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1 | <?xml version="1.0" encoding="UTF-8"?> |
2 | <!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN" | |
3 | "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" []> | |
1da177e4 LT |
4 | |
5 | <!-- ****************************************************** --> | |
6 | <!-- Header --> | |
7 | <!-- ****************************************************** --> | |
5f8206c0 | 8 | <book id="Writing-an-ALSA-Driver"> |
1da177e4 LT |
9 | <bookinfo> |
10 | <title>Writing an ALSA Driver</title> | |
11 | <author> | |
12 | <firstname>Takashi</firstname> | |
13 | <surname>Iwai</surname> | |
14 | <affiliation> | |
15 | <address> | |
16 | <email>tiwai@suse.de</email> | |
17 | </address> | |
18 | </affiliation> | |
19 | </author> | |
20 | ||
3f03f7c5 | 21 | <date>Oct 15, 2007</date> |
d1761d1b | 22 | <edition>0.3.7</edition> |
1da177e4 LT |
23 | |
24 | <abstract> | |
25 | <para> | |
26 | This document describes how to write an ALSA (Advanced Linux | |
27 | Sound Architecture) driver. | |
28 | </para> | |
29 | </abstract> | |
30 | ||
31 | <legalnotice> | |
32 | <para> | |
7c22f1aa | 33 | Copyright (c) 2002-2005 Takashi Iwai <email>tiwai@suse.de</email> |
1da177e4 LT |
34 | </para> |
35 | ||
36 | <para> | |
37 | This document is free; you can redistribute it and/or modify it | |
38 | under the terms of the GNU General Public License as published by | |
39 | the Free Software Foundation; either version 2 of the License, or | |
40 | (at your option) any later version. | |
41 | </para> | |
42 | ||
43 | <para> | |
44 | This document is distributed in the hope that it will be useful, | |
45 | but <emphasis>WITHOUT ANY WARRANTY</emphasis>; without even the | |
46 | implied warranty of <emphasis>MERCHANTABILITY or FITNESS FOR A | |
47 | PARTICULAR PURPOSE</emphasis>. See the GNU General Public License | |
48 | for more details. | |
49 | </para> | |
50 | ||
51 | <para> | |
52 | You should have received a copy of the GNU General Public | |
53 | License along with this program; if not, write to the Free | |
54 | Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, | |
55 | MA 02111-1307 USA | |
56 | </para> | |
57 | </legalnotice> | |
58 | ||
59 | </bookinfo> | |
60 | ||
61 | <!-- ****************************************************** --> | |
62 | <!-- Preface --> | |
63 | <!-- ****************************************************** --> | |
64 | <preface id="preface"> | |
65 | <title>Preface</title> | |
66 | <para> | |
67 | This document describes how to write an | |
68 | <ulink url="http://www.alsa-project.org/"><citetitle> | |
69 | ALSA (Advanced Linux Sound Architecture)</citetitle></ulink> | |
3f03f7c5 | 70 | driver. The document focuses mainly on PCI soundcards. |
1da177e4 LT |
71 | In the case of other device types, the API might |
72 | be different, too. However, at least the ALSA kernel API is | |
73 | consistent, and therefore it would be still a bit help for | |
74 | writing them. | |
75 | </para> | |
76 | ||
77 | <para> | |
3f03f7c5 MO |
78 | This document targets people who already have enough |
79 | C language skills and have basic linux kernel programming | |
80 | knowledge. This document doesn't explain the general | |
81 | topic of linux kernel coding and doesn't cover low-level | |
82 | driver implementation details. It only describes | |
1da177e4 LT |
83 | the standard way to write a PCI sound driver on ALSA. |
84 | </para> | |
85 | ||
86 | <para> | |
3f03f7c5 MO |
87 | If you are already familiar with the older ALSA ver.0.5.x API, you |
88 | can check the drivers such as <filename>sound/pci/es1938.c</filename> or | |
89 | <filename>sound/pci/maestro3.c</filename> which have also almost the same | |
1da177e4 LT |
90 | code-base in the ALSA 0.5.x tree, so you can compare the differences. |
91 | </para> | |
92 | ||
93 | <para> | |
3f03f7c5 | 94 | This document is still a draft version. Any feedback and |
1da177e4 LT |
95 | corrections, please!! |
96 | </para> | |
97 | </preface> | |
98 | ||
99 | ||
100 | <!-- ****************************************************** --> | |
101 | <!-- File Tree Structure --> | |
102 | <!-- ****************************************************** --> | |
103 | <chapter id="file-tree"> | |
104 | <title>File Tree Structure</title> | |
105 | ||
106 | <section id="file-tree-general"> | |
107 | <title>General</title> | |
108 | <para> | |
3f03f7c5 | 109 | The ALSA drivers are provided in two ways. |
1da177e4 LT |
110 | </para> |
111 | ||
112 | <para> | |
113 | One is the trees provided as a tarball or via cvs from the | |
114 | ALSA's ftp site, and another is the 2.6 (or later) Linux kernel | |
115 | tree. To synchronize both, the ALSA driver tree is split into | |
116 | two different trees: alsa-kernel and alsa-driver. The former | |
3f03f7c5 | 117 | contains purely the source code for the Linux 2.6 (or later) |
1da177e4 LT |
118 | tree. This tree is designed only for compilation on 2.6 or |
119 | later environment. The latter, alsa-driver, contains many subtle | |
3f03f7c5 MO |
120 | files for compiling ALSA drivers outside of the Linux kernel tree, |
121 | wrapper functions for older 2.2 and 2.4 kernels, to adapt the latest kernel API, | |
1da177e4 LT |
122 | and additional drivers which are still in development or in |
123 | tests. The drivers in alsa-driver tree will be moved to | |
3f03f7c5 | 124 | alsa-kernel (and eventually to the 2.6 kernel tree) when they are |
1da177e4 LT |
125 | finished and confirmed to work fine. |
126 | </para> | |
127 | ||
128 | <para> | |
129 | The file tree structure of ALSA driver is depicted below. Both | |
130 | alsa-kernel and alsa-driver have almost the same file | |
131 | structure, except for <quote>core</quote> directory. It's | |
132 | named as <quote>acore</quote> in alsa-driver tree. | |
133 | ||
134 | <example> | |
135 | <title>ALSA File Tree Structure</title> | |
136 | <literallayout> | |
137 | sound | |
138 | /core | |
139 | /oss | |
140 | /seq | |
141 | /oss | |
142 | /instr | |
143 | /ioctl32 | |
144 | /include | |
145 | /drivers | |
146 | /mpu401 | |
147 | /opl3 | |
148 | /i2c | |
149 | /l3 | |
150 | /synth | |
151 | /emux | |
152 | /pci | |
153 | /(cards) | |
154 | /isa | |
155 | /(cards) | |
156 | /arm | |
157 | /ppc | |
158 | /sparc | |
159 | /usb | |
160 | /pcmcia /(cards) | |
161 | /oss | |
162 | </literallayout> | |
163 | </example> | |
164 | </para> | |
165 | </section> | |
166 | ||
167 | <section id="file-tree-core-directory"> | |
168 | <title>core directory</title> | |
169 | <para> | |
3f03f7c5 | 170 | This directory contains the middle layer which is the heart |
1da177e4 LT |
171 | of ALSA drivers. In this directory, the native ALSA modules are |
172 | stored. The sub-directories contain different modules and are | |
173 | dependent upon the kernel config. | |
174 | </para> | |
175 | ||
176 | <section id="file-tree-core-directory-oss"> | |
177 | <title>core/oss</title> | |
178 | ||
179 | <para> | |
180 | The codes for PCM and mixer OSS emulation modules are stored | |
181 | in this directory. The rawmidi OSS emulation is included in | |
182 | the ALSA rawmidi code since it's quite small. The sequencer | |
3f03f7c5 | 183 | code is stored in <filename>core/seq/oss</filename> directory (see |
1da177e4 LT |
184 | <link linkend="file-tree-core-directory-seq-oss"><citetitle> |
185 | below</citetitle></link>). | |
186 | </para> | |
187 | </section> | |
188 | ||
189 | <section id="file-tree-core-directory-ioctl32"> | |
190 | <title>core/ioctl32</title> | |
191 | ||
192 | <para> | |
193 | This directory contains the 32bit-ioctl wrappers for 64bit | |
194 | architectures such like x86-64, ppc64 and sparc64. For 32bit | |
195 | and alpha architectures, these are not compiled. | |
196 | </para> | |
197 | </section> | |
198 | ||
199 | <section id="file-tree-core-directory-seq"> | |
200 | <title>core/seq</title> | |
201 | <para> | |
3f03f7c5 | 202 | This directory and its sub-directories are for the ALSA |
1da177e4 LT |
203 | sequencer. This directory contains the sequencer core and |
204 | primary sequencer modules such like snd-seq-midi, | |
205 | snd-seq-virmidi, etc. They are compiled only when | |
206 | <constant>CONFIG_SND_SEQUENCER</constant> is set in the kernel | |
207 | config. | |
208 | </para> | |
209 | </section> | |
210 | ||
211 | <section id="file-tree-core-directory-seq-oss"> | |
212 | <title>core/seq/oss</title> | |
213 | <para> | |
214 | This contains the OSS sequencer emulation codes. | |
215 | </para> | |
216 | </section> | |
217 | ||
218 | <section id="file-tree-core-directory-deq-instr"> | |
219 | <title>core/seq/instr</title> | |
220 | <para> | |
221 | This directory contains the modules for the sequencer | |
222 | instrument layer. | |
223 | </para> | |
224 | </section> | |
225 | </section> | |
226 | ||
227 | <section id="file-tree-include-directory"> | |
228 | <title>include directory</title> | |
229 | <para> | |
230 | This is the place for the public header files of ALSA drivers, | |
3f03f7c5 | 231 | which are to be exported to user-space, or included by |
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232 | several files at different directories. Basically, the private |
233 | header files should not be placed in this directory, but you may | |
3f03f7c5 | 234 | still find files there, due to historical reasons :) |
1da177e4 LT |
235 | </para> |
236 | </section> | |
237 | ||
238 | <section id="file-tree-drivers-directory"> | |
239 | <title>drivers directory</title> | |
240 | <para> | |
3f03f7c5 MO |
241 | This directory contains code shared among different drivers |
242 | on different architectures. They are hence supposed not to be | |
1da177e4 LT |
243 | architecture-specific. |
244 | For example, the dummy pcm driver and the serial MIDI | |
245 | driver are found in this directory. In the sub-directories, | |
3f03f7c5 | 246 | there is code for components which are independent from |
1da177e4 LT |
247 | bus and cpu architectures. |
248 | </para> | |
249 | ||
250 | <section id="file-tree-drivers-directory-mpu401"> | |
251 | <title>drivers/mpu401</title> | |
252 | <para> | |
253 | The MPU401 and MPU401-UART modules are stored here. | |
254 | </para> | |
255 | </section> | |
256 | ||
257 | <section id="file-tree-drivers-directory-opl3"> | |
258 | <title>drivers/opl3 and opl4</title> | |
259 | <para> | |
260 | The OPL3 and OPL4 FM-synth stuff is found here. | |
261 | </para> | |
262 | </section> | |
263 | </section> | |
264 | ||
265 | <section id="file-tree-i2c-directory"> | |
266 | <title>i2c directory</title> | |
267 | <para> | |
268 | This contains the ALSA i2c components. | |
269 | </para> | |
270 | ||
271 | <para> | |
272 | Although there is a standard i2c layer on Linux, ALSA has its | |
3f03f7c5 | 273 | own i2c code for some cards, because the soundcard needs only a |
1da177e4 LT |
274 | simple operation and the standard i2c API is too complicated for |
275 | such a purpose. | |
276 | </para> | |
277 | ||
278 | <section id="file-tree-i2c-directory-l3"> | |
279 | <title>i2c/l3</title> | |
280 | <para> | |
281 | This is a sub-directory for ARM L3 i2c. | |
282 | </para> | |
283 | </section> | |
284 | </section> | |
285 | ||
286 | <section id="file-tree-synth-directory"> | |
287 | <title>synth directory</title> | |
288 | <para> | |
289 | This contains the synth middle-level modules. | |
290 | </para> | |
291 | ||
292 | <para> | |
293 | So far, there is only Emu8000/Emu10k1 synth driver under | |
3f03f7c5 | 294 | the <filename>synth/emux</filename> sub-directory. |
1da177e4 LT |
295 | </para> |
296 | </section> | |
297 | ||
298 | <section id="file-tree-pci-directory"> | |
299 | <title>pci directory</title> | |
300 | <para> | |
3f03f7c5 MO |
301 | This directory and its sub-directories hold the top-level card modules |
302 | for PCI soundcards and the code specific to the PCI BUS. | |
1da177e4 LT |
303 | </para> |
304 | ||
305 | <para> | |
3f03f7c5 MO |
306 | The drivers compiled from a single file are stored directly |
307 | in the pci directory, while the drivers with several source files are | |
308 | stored on their own sub-directory (e.g. emu10k1, ice1712). | |
1da177e4 LT |
309 | </para> |
310 | </section> | |
311 | ||
312 | <section id="file-tree-isa-directory"> | |
313 | <title>isa directory</title> | |
314 | <para> | |
3f03f7c5 | 315 | This directory and its sub-directories hold the top-level card modules |
1da177e4 LT |
316 | for ISA soundcards. |
317 | </para> | |
318 | </section> | |
319 | ||
320 | <section id="file-tree-arm-ppc-sparc-directories"> | |
321 | <title>arm, ppc, and sparc directories</title> | |
322 | <para> | |
3f03f7c5 MO |
323 | They are used for top-level card modules which are |
324 | specific to one of these architectures. | |
1da177e4 LT |
325 | </para> |
326 | </section> | |
327 | ||
328 | <section id="file-tree-usb-directory"> | |
329 | <title>usb directory</title> | |
330 | <para> | |
3f03f7c5 MO |
331 | This directory contains the USB-audio driver. In the latest version, the |
332 | USB MIDI driver is integrated in the usb-audio driver. | |
1da177e4 LT |
333 | </para> |
334 | </section> | |
335 | ||
336 | <section id="file-tree-pcmcia-directory"> | |
337 | <title>pcmcia directory</title> | |
338 | <para> | |
339 | The PCMCIA, especially PCCard drivers will go here. CardBus | |
3f03f7c5 MO |
340 | drivers will be in the pci directory, because their API is identical |
341 | to that of standard PCI cards. | |
1da177e4 LT |
342 | </para> |
343 | </section> | |
344 | ||
345 | <section id="file-tree-oss-directory"> | |
346 | <title>oss directory</title> | |
347 | <para> | |
3f03f7c5 MO |
348 | The OSS/Lite source files are stored here in Linux 2.6 (or |
349 | later) tree. In the ALSA driver tarball, this directory is empty, | |
350 | of course :) | |
1da177e4 LT |
351 | </para> |
352 | </section> | |
353 | </chapter> | |
354 | ||
355 | ||
356 | <!-- ****************************************************** --> | |
357 | <!-- Basic Flow for PCI Drivers --> | |
358 | <!-- ****************************************************** --> | |
359 | <chapter id="basic-flow"> | |
360 | <title>Basic Flow for PCI Drivers</title> | |
361 | ||
362 | <section id="basic-flow-outline"> | |
363 | <title>Outline</title> | |
364 | <para> | |
3f03f7c5 | 365 | The minimum flow for PCI soundcards is as follows: |
1da177e4 LT |
366 | |
367 | <itemizedlist> | |
368 | <listitem><para>define the PCI ID table (see the section | |
369 | <link linkend="pci-resource-entries"><citetitle>PCI Entries | |
370 | </citetitle></link>).</para></listitem> | |
371 | <listitem><para>create <function>probe()</function> callback.</para></listitem> | |
372 | <listitem><para>create <function>remove()</function> callback.</para></listitem> | |
3f03f7c5 MO |
373 | <listitem><para>create a <structname>pci_driver</structname> structure |
374 | containing the three pointers above.</para></listitem> | |
375 | <listitem><para>create an <function>init()</function> function just calling | |
376 | the <function>pci_register_driver()</function> to register the pci_driver table | |
377 | defined above.</para></listitem> | |
378 | <listitem><para>create an <function>exit()</function> function to call | |
379 | the <function>pci_unregister_driver()</function> function.</para></listitem> | |
1da177e4 LT |
380 | </itemizedlist> |
381 | </para> | |
382 | </section> | |
383 | ||
384 | <section id="basic-flow-example"> | |
385 | <title>Full Code Example</title> | |
386 | <para> | |
387 | The code example is shown below. Some parts are kept | |
388 | unimplemented at this moment but will be filled in the | |
3f03f7c5 MO |
389 | next sections. The numbers in the comment lines of the |
390 | <function>snd_mychip_probe()</function> function | |
391 | refer to details explained in the following section. | |
1da177e4 LT |
392 | |
393 | <example> | |
3f03f7c5 | 394 | <title>Basic Flow for PCI Drivers - Example</title> |
1da177e4 LT |
395 | <programlisting> |
396 | <![CDATA[ | |
1da177e4 LT |
397 | #include <linux/init.h> |
398 | #include <linux/pci.h> | |
399 | #include <linux/slab.h> | |
400 | #include <sound/core.h> | |
401 | #include <sound/initval.h> | |
402 | ||
403 | /* module parameters (see "Module Parameters") */ | |
3f03f7c5 | 404 | /* SNDRV_CARDS: maximum number of cards supported by this module */ |
1da177e4 LT |
405 | static int index[SNDRV_CARDS] = SNDRV_DEFAULT_IDX; |
406 | static char *id[SNDRV_CARDS] = SNDRV_DEFAULT_STR; | |
a67ff6a5 | 407 | static bool enable[SNDRV_CARDS] = SNDRV_DEFAULT_ENABLE_PNP; |
1da177e4 LT |
408 | |
409 | /* definition of the chip-specific record */ | |
446ab5f5 TI |
410 | struct mychip { |
411 | struct snd_card *card; | |
3f03f7c5 MO |
412 | /* the rest of the implementation will be in section |
413 | * "PCI Resource Management" | |
95a5b085 | 414 | */ |
1da177e4 LT |
415 | }; |
416 | ||
417 | /* chip-specific destructor | |
3f03f7c5 | 418 | * (see "PCI Resource Management") |
1da177e4 | 419 | */ |
446ab5f5 | 420 | static int snd_mychip_free(struct mychip *chip) |
1da177e4 | 421 | { |
95a5b085 | 422 | .... /* will be implemented later... */ |
1da177e4 LT |
423 | } |
424 | ||
425 | /* component-destructor | |
426 | * (see "Management of Cards and Components") | |
427 | */ | |
446ab5f5 | 428 | static int snd_mychip_dev_free(struct snd_device *device) |
1da177e4 | 429 | { |
446ab5f5 | 430 | return snd_mychip_free(device->device_data); |
1da177e4 LT |
431 | } |
432 | ||
433 | /* chip-specific constructor | |
434 | * (see "Management of Cards and Components") | |
435 | */ | |
090015ae TI |
436 | static int snd_mychip_create(struct snd_card *card, |
437 | struct pci_dev *pci, | |
438 | struct mychip **rchip) | |
1da177e4 | 439 | { |
446ab5f5 | 440 | struct mychip *chip; |
1da177e4 | 441 | int err; |
446ab5f5 | 442 | static struct snd_device_ops ops = { |
1da177e4 LT |
443 | .dev_free = snd_mychip_dev_free, |
444 | }; | |
445 | ||
446 | *rchip = NULL; | |
447 | ||
95a5b085 | 448 | /* check PCI availability here |
3f03f7c5 | 449 | * (see "PCI Resource Management") |
95a5b085 | 450 | */ |
1da177e4 LT |
451 | .... |
452 | ||
453 | /* allocate a chip-specific data with zero filled */ | |
561b220a | 454 | chip = kzalloc(sizeof(*chip), GFP_KERNEL); |
1da177e4 LT |
455 | if (chip == NULL) |
456 | return -ENOMEM; | |
457 | ||
458 | chip->card = card; | |
459 | ||
95a5b085 | 460 | /* rest of initialization here; will be implemented |
3f03f7c5 | 461 | * later, see "PCI Resource Management" |
95a5b085 | 462 | */ |
1da177e4 LT |
463 | .... |
464 | ||
95a5b085 TI |
465 | err = snd_device_new(card, SNDRV_DEV_LOWLEVEL, chip, &ops); |
466 | if (err < 0) { | |
1da177e4 LT |
467 | snd_mychip_free(chip); |
468 | return err; | |
469 | } | |
470 | ||
1da177e4 LT |
471 | *rchip = chip; |
472 | return 0; | |
473 | } | |
474 | ||
475 | /* constructor -- see "Constructor" sub-section */ | |
090015ae TI |
476 | static int snd_mychip_probe(struct pci_dev *pci, |
477 | const struct pci_device_id *pci_id) | |
1da177e4 LT |
478 | { |
479 | static int dev; | |
446ab5f5 TI |
480 | struct snd_card *card; |
481 | struct mychip *chip; | |
1da177e4 LT |
482 | int err; |
483 | ||
484 | /* (1) */ | |
485 | if (dev >= SNDRV_CARDS) | |
486 | return -ENODEV; | |
487 | if (!enable[dev]) { | |
488 | dev++; | |
489 | return -ENOENT; | |
490 | } | |
491 | ||
492 | /* (2) */ | |
393aa9c1 TI |
493 | err = snd_card_new(&pci->dev, index[dev], id[dev], THIS_MODULE, |
494 | 0, &card); | |
d453379b TI |
495 | if (err < 0) |
496 | return err; | |
1da177e4 LT |
497 | |
498 | /* (3) */ | |
95a5b085 TI |
499 | err = snd_mychip_create(card, pci, &chip); |
500 | if (err < 0) { | |
1da177e4 LT |
501 | snd_card_free(card); |
502 | return err; | |
503 | } | |
504 | ||
505 | /* (4) */ | |
506 | strcpy(card->driver, "My Chip"); | |
507 | strcpy(card->shortname, "My Own Chip 123"); | |
508 | sprintf(card->longname, "%s at 0x%lx irq %i", | |
509 | card->shortname, chip->ioport, chip->irq); | |
510 | ||
511 | /* (5) */ | |
95a5b085 | 512 | .... /* implemented later */ |
1da177e4 LT |
513 | |
514 | /* (6) */ | |
95a5b085 TI |
515 | err = snd_card_register(card); |
516 | if (err < 0) { | |
1da177e4 LT |
517 | snd_card_free(card); |
518 | return err; | |
519 | } | |
520 | ||
521 | /* (7) */ | |
522 | pci_set_drvdata(pci, card); | |
523 | dev++; | |
524 | return 0; | |
525 | } | |
526 | ||
3f03f7c5 | 527 | /* destructor -- see the "Destructor" sub-section */ |
090015ae | 528 | static void snd_mychip_remove(struct pci_dev *pci) |
1da177e4 LT |
529 | { |
530 | snd_card_free(pci_get_drvdata(pci)); | |
531 | pci_set_drvdata(pci, NULL); | |
532 | } | |
533 | ]]> | |
534 | </programlisting> | |
535 | </example> | |
536 | </para> | |
537 | </section> | |
538 | ||
539 | <section id="basic-flow-constructor"> | |
540 | <title>Constructor</title> | |
541 | <para> | |
3f03f7c5 MO |
542 | The real constructor of PCI drivers is the <function>probe</function> callback. |
543 | The <function>probe</function> callback and other component-constructors which are called | |
090015ae TI |
544 | from the <function>probe</function> callback cannot be used with |
545 | the <parameter>__init</parameter> prefix | |
1da177e4 LT |
546 | because any PCI device could be a hotplug device. |
547 | </para> | |
548 | ||
549 | <para> | |
3f03f7c5 | 550 | In the <function>probe</function> callback, the following scheme is often used. |
1da177e4 LT |
551 | </para> |
552 | ||
553 | <section id="basic-flow-constructor-device-index"> | |
554 | <title>1) Check and increment the device index.</title> | |
555 | <para> | |
556 | <informalexample> | |
557 | <programlisting> | |
558 | <![CDATA[ | |
559 | static int dev; | |
560 | .... | |
561 | if (dev >= SNDRV_CARDS) | |
562 | return -ENODEV; | |
563 | if (!enable[dev]) { | |
564 | dev++; | |
565 | return -ENOENT; | |
566 | } | |
567 | ]]> | |
568 | </programlisting> | |
569 | </informalexample> | |
570 | ||
571 | where enable[dev] is the module option. | |
572 | </para> | |
573 | ||
574 | <para> | |
3f03f7c5 | 575 | Each time the <function>probe</function> callback is called, check the |
1da177e4 LT |
576 | availability of the device. If not available, simply increment |
577 | the device index and returns. dev will be incremented also | |
578 | later (<link | |
579 | linkend="basic-flow-constructor-set-pci"><citetitle>step | |
580 | 7</citetitle></link>). | |
581 | </para> | |
582 | </section> | |
583 | ||
584 | <section id="basic-flow-constructor-create-card"> | |
585 | <title>2) Create a card instance</title> | |
586 | <para> | |
587 | <informalexample> | |
588 | <programlisting> | |
589 | <![CDATA[ | |
446ab5f5 | 590 | struct snd_card *card; |
d453379b | 591 | int err; |
1da177e4 | 592 | .... |
393aa9c1 TI |
593 | err = snd_card_new(&pci->dev, index[dev], id[dev], THIS_MODULE, |
594 | 0, &card); | |
1da177e4 LT |
595 | ]]> |
596 | </programlisting> | |
597 | </informalexample> | |
598 | </para> | |
599 | ||
600 | <para> | |
3f03f7c5 | 601 | The details will be explained in the section |
1da177e4 LT |
602 | <link linkend="card-management-card-instance"><citetitle> |
603 | Management of Cards and Components</citetitle></link>. | |
604 | </para> | |
605 | </section> | |
606 | ||
607 | <section id="basic-flow-constructor-create-main"> | |
608 | <title>3) Create a main component</title> | |
609 | <para> | |
610 | In this part, the PCI resources are allocated. | |
611 | ||
612 | <informalexample> | |
613 | <programlisting> | |
614 | <![CDATA[ | |
446ab5f5 | 615 | struct mychip *chip; |
1da177e4 | 616 | .... |
95a5b085 TI |
617 | err = snd_mychip_create(card, pci, &chip); |
618 | if (err < 0) { | |
1da177e4 LT |
619 | snd_card_free(card); |
620 | return err; | |
621 | } | |
622 | ]]> | |
623 | </programlisting> | |
624 | </informalexample> | |
625 | ||
3f03f7c5 | 626 | The details will be explained in the section <link |
1da177e4 | 627 | linkend="pci-resource"><citetitle>PCI Resource |
3f03f7c5 | 628 | Management</citetitle></link>. |
1da177e4 LT |
629 | </para> |
630 | </section> | |
631 | ||
632 | <section id="basic-flow-constructor-main-component"> | |
633 | <title>4) Set the driver ID and name strings.</title> | |
634 | <para> | |
635 | <informalexample> | |
636 | <programlisting> | |
637 | <![CDATA[ | |
638 | strcpy(card->driver, "My Chip"); | |
639 | strcpy(card->shortname, "My Own Chip 123"); | |
640 | sprintf(card->longname, "%s at 0x%lx irq %i", | |
641 | card->shortname, chip->ioport, chip->irq); | |
642 | ]]> | |
643 | </programlisting> | |
644 | </informalexample> | |
645 | ||
646 | The driver field holds the minimal ID string of the | |
3f03f7c5 | 647 | chip. This is used by alsa-lib's configurator, so keep it |
1da177e4 LT |
648 | simple but unique. |
649 | Even the same driver can have different driver IDs to | |
650 | distinguish the functionality of each chip type. | |
651 | </para> | |
652 | ||
653 | <para> | |
654 | The shortname field is a string shown as more verbose | |
3f03f7c5 | 655 | name. The longname field contains the information |
1da177e4 LT |
656 | shown in <filename>/proc/asound/cards</filename>. |
657 | </para> | |
658 | </section> | |
659 | ||
660 | <section id="basic-flow-constructor-create-other"> | |
661 | <title>5) Create other components, such as mixer, MIDI, etc.</title> | |
662 | <para> | |
663 | Here you define the basic components such as | |
664 | <link linkend="pcm-interface"><citetitle>PCM</citetitle></link>, | |
665 | mixer (e.g. <link linkend="api-ac97"><citetitle>AC97</citetitle></link>), | |
666 | MIDI (e.g. <link linkend="midi-interface"><citetitle>MPU-401</citetitle></link>), | |
667 | and other interfaces. | |
668 | Also, if you want a <link linkend="proc-interface"><citetitle>proc | |
669 | file</citetitle></link>, define it here, too. | |
670 | </para> | |
671 | </section> | |
672 | ||
673 | <section id="basic-flow-constructor-register-card"> | |
674 | <title>6) Register the card instance.</title> | |
675 | <para> | |
676 | <informalexample> | |
677 | <programlisting> | |
678 | <![CDATA[ | |
95a5b085 TI |
679 | err = snd_card_register(card); |
680 | if (err < 0) { | |
1da177e4 LT |
681 | snd_card_free(card); |
682 | return err; | |
683 | } | |
684 | ]]> | |
685 | </programlisting> | |
686 | </informalexample> | |
687 | </para> | |
688 | ||
689 | <para> | |
690 | Will be explained in the section <link | |
691 | linkend="card-management-registration"><citetitle>Management | |
692 | of Cards and Components</citetitle></link>, too. | |
693 | </para> | |
694 | </section> | |
695 | ||
696 | <section id="basic-flow-constructor-set-pci"> | |
697 | <title>7) Set the PCI driver data and return zero.</title> | |
698 | <para> | |
699 | <informalexample> | |
700 | <programlisting> | |
701 | <![CDATA[ | |
702 | pci_set_drvdata(pci, card); | |
703 | dev++; | |
704 | return 0; | |
705 | ]]> | |
706 | </programlisting> | |
707 | </informalexample> | |
708 | ||
709 | In the above, the card record is stored. This pointer is | |
3f03f7c5 | 710 | used in the remove callback and power-management |
1da177e4 LT |
711 | callbacks, too. |
712 | </para> | |
713 | </section> | |
714 | </section> | |
715 | ||
716 | <section id="basic-flow-destructor"> | |
717 | <title>Destructor</title> | |
718 | <para> | |
719 | The destructor, remove callback, simply releases the card | |
720 | instance. Then the ALSA middle layer will release all the | |
721 | attached components automatically. | |
722 | </para> | |
723 | ||
724 | <para> | |
725 | It would be typically like the following: | |
726 | ||
727 | <informalexample> | |
728 | <programlisting> | |
729 | <![CDATA[ | |
090015ae | 730 | static void snd_mychip_remove(struct pci_dev *pci) |
1da177e4 LT |
731 | { |
732 | snd_card_free(pci_get_drvdata(pci)); | |
733 | pci_set_drvdata(pci, NULL); | |
734 | } | |
735 | ]]> | |
736 | </programlisting> | |
737 | </informalexample> | |
738 | ||
739 | The above code assumes that the card pointer is set to the PCI | |
740 | driver data. | |
741 | </para> | |
742 | </section> | |
743 | ||
744 | <section id="basic-flow-header-files"> | |
745 | <title>Header Files</title> | |
746 | <para> | |
747 | For the above example, at least the following include files | |
748 | are necessary. | |
749 | ||
750 | <informalexample> | |
751 | <programlisting> | |
752 | <![CDATA[ | |
1da177e4 LT |
753 | #include <linux/init.h> |
754 | #include <linux/pci.h> | |
755 | #include <linux/slab.h> | |
756 | #include <sound/core.h> | |
757 | #include <sound/initval.h> | |
758 | ]]> | |
759 | </programlisting> | |
760 | </informalexample> | |
761 | ||
762 | where the last one is necessary only when module options are | |
3f03f7c5 MO |
763 | defined in the source file. If the code is split into several |
764 | files, the files without module options don't need them. | |
1da177e4 LT |
765 | </para> |
766 | ||
767 | <para> | |
3f03f7c5 MO |
768 | In addition to these headers, you'll need |
769 | <filename><linux/interrupt.h></filename> for interrupt | |
770 | handling, and <filename><asm/io.h></filename> for I/O | |
771 | access. If you use the <function>mdelay()</function> or | |
1da177e4 | 772 | <function>udelay()</function> functions, you'll need to include |
3f03f7c5 | 773 | <filename><linux/delay.h></filename> too. |
1da177e4 LT |
774 | </para> |
775 | ||
776 | <para> | |
3f03f7c5 MO |
777 | The ALSA interfaces like the PCM and control APIs are defined in other |
778 | <filename><sound/xxx.h></filename> header files. | |
1da177e4 LT |
779 | They have to be included after |
780 | <filename><sound/core.h></filename>. | |
781 | </para> | |
782 | ||
783 | </section> | |
784 | </chapter> | |
785 | ||
786 | ||
787 | <!-- ****************************************************** --> | |
788 | <!-- Management of Cards and Components --> | |
789 | <!-- ****************************************************** --> | |
790 | <chapter id="card-management"> | |
791 | <title>Management of Cards and Components</title> | |
792 | ||
793 | <section id="card-management-card-instance"> | |
794 | <title>Card Instance</title> | |
795 | <para> | |
796 | For each soundcard, a <quote>card</quote> record must be allocated. | |
797 | </para> | |
798 | ||
799 | <para> | |
800 | A card record is the headquarters of the soundcard. It manages | |
3f03f7c5 | 801 | the whole list of devices (components) on the soundcard, such as |
1da177e4 LT |
802 | PCM, mixers, MIDI, synthesizer, and so on. Also, the card |
803 | record holds the ID and the name strings of the card, manages | |
804 | the root of proc files, and controls the power-management states | |
805 | and hotplug disconnections. The component list on the card | |
3f03f7c5 | 806 | record is used to manage the correct release of resources at |
1da177e4 LT |
807 | destruction. |
808 | </para> | |
809 | ||
810 | <para> | |
811 | As mentioned above, to create a card instance, call | |
393aa9c1 | 812 | <function>snd_card_new()</function>. |
1da177e4 LT |
813 | |
814 | <informalexample> | |
815 | <programlisting> | |
816 | <![CDATA[ | |
446ab5f5 | 817 | struct snd_card *card; |
d453379b | 818 | int err; |
393aa9c1 | 819 | err = snd_card_new(&pci->dev, index, id, module, extra_size, &card); |
1da177e4 LT |
820 | ]]> |
821 | </programlisting> | |
822 | </informalexample> | |
823 | </para> | |
824 | ||
825 | <para> | |
393aa9c1 TI |
826 | The function takes six arguments: the parent device pointer, |
827 | the card-index number, the id string, the module pointer (usually | |
1da177e4 | 828 | <constant>THIS_MODULE</constant>), |
d453379b TI |
829 | the size of extra-data space, and the pointer to return the |
830 | card instance. The extra_size argument is used to | |
1da177e4 | 831 | allocate card->private_data for the |
3f03f7c5 | 832 | chip-specific data. Note that these data |
393aa9c1 TI |
833 | are allocated by <function>snd_card_new()</function>. |
834 | </para> | |
835 | ||
836 | <para> | |
837 | The first argument, the pointer of struct | |
838 | <structname>device</structname>, specifies the parent device. | |
839 | For PCI devices, typically &pci-> is passed there. | |
1da177e4 LT |
840 | </para> |
841 | </section> | |
842 | ||
843 | <section id="card-management-component"> | |
844 | <title>Components</title> | |
845 | <para> | |
846 | After the card is created, you can attach the components | |
3f03f7c5 | 847 | (devices) to the card instance. In an ALSA driver, a component is |
446ab5f5 | 848 | represented as a struct <structname>snd_device</structname> object. |
1da177e4 | 849 | A component can be a PCM instance, a control interface, a raw |
3f03f7c5 | 850 | MIDI interface, etc. Each such instance has one component |
1da177e4 LT |
851 | entry. |
852 | </para> | |
853 | ||
854 | <para> | |
855 | A component can be created via | |
856 | <function>snd_device_new()</function> function. | |
857 | ||
858 | <informalexample> | |
859 | <programlisting> | |
860 | <![CDATA[ | |
861 | snd_device_new(card, SNDRV_DEV_XXX, chip, &ops); | |
862 | ]]> | |
863 | </programlisting> | |
864 | </informalexample> | |
865 | </para> | |
866 | ||
867 | <para> | |
868 | This takes the card pointer, the device-level | |
869 | (<constant>SNDRV_DEV_XXX</constant>), the data pointer, and the | |
870 | callback pointers (<parameter>&ops</parameter>). The | |
871 | device-level defines the type of components and the order of | |
3f03f7c5 | 872 | registration and de-registration. For most components, the |
1da177e4 LT |
873 | device-level is already defined. For a user-defined component, |
874 | you can use <constant>SNDRV_DEV_LOWLEVEL</constant>. | |
875 | </para> | |
876 | ||
877 | <para> | |
878 | This function itself doesn't allocate the data space. The data | |
879 | must be allocated manually beforehand, and its pointer is passed | |
04044b81 AO |
880 | as the argument. This pointer (<parameter>chip</parameter> in the |
881 | above example) is used as the identifier for the instance. | |
1da177e4 LT |
882 | </para> |
883 | ||
884 | <para> | |
3f03f7c5 | 885 | Each pre-defined ALSA component such as ac97 and pcm calls |
1da177e4 LT |
886 | <function>snd_device_new()</function> inside its |
887 | constructor. The destructor for each component is defined in the | |
888 | callback pointers. Hence, you don't need to take care of | |
889 | calling a destructor for such a component. | |
890 | </para> | |
891 | ||
892 | <para> | |
3f03f7c5 MO |
893 | If you wish to create your own component, you need to |
894 | set the destructor function to the dev_free callback in | |
895 | the <parameter>ops</parameter>, so that it can be released | |
896 | automatically via <function>snd_card_free()</function>. | |
897 | The next example will show an implementation of chip-specific | |
898 | data. | |
1da177e4 LT |
899 | </para> |
900 | </section> | |
901 | ||
902 | <section id="card-management-chip-specific"> | |
903 | <title>Chip-Specific Data</title> | |
904 | <para> | |
3f03f7c5 | 905 | Chip-specific information, e.g. the I/O port address, its |
1da177e4 LT |
906 | resource pointer, or the irq number, is stored in the |
907 | chip-specific record. | |
1da177e4 LT |
908 | |
909 | <informalexample> | |
910 | <programlisting> | |
911 | <![CDATA[ | |
446ab5f5 | 912 | struct mychip { |
1da177e4 LT |
913 | .... |
914 | }; | |
915 | ]]> | |
916 | </programlisting> | |
917 | </informalexample> | |
918 | </para> | |
919 | ||
920 | <para> | |
3f03f7c5 | 921 | In general, there are two ways of allocating the chip record. |
1da177e4 LT |
922 | </para> |
923 | ||
924 | <section id="card-management-chip-specific-snd-card-new"> | |
393aa9c1 | 925 | <title>1. Allocating via <function>snd_card_new()</function>.</title> |
1da177e4 | 926 | <para> |
3f03f7c5 | 927 | As mentioned above, you can pass the extra-data-length |
393aa9c1 | 928 | to the 5th argument of <function>snd_card_new()</function>, i.e. |
1da177e4 LT |
929 | |
930 | <informalexample> | |
931 | <programlisting> | |
932 | <![CDATA[ | |
393aa9c1 TI |
933 | err = snd_card_new(&pci->dev, index[dev], id[dev], THIS_MODULE, |
934 | sizeof(struct mychip), &card); | |
1da177e4 LT |
935 | ]]> |
936 | </programlisting> | |
937 | </informalexample> | |
938 | ||
3f03f7c5 | 939 | struct <structname>mychip</structname> is the type of the chip record. |
1da177e4 LT |
940 | </para> |
941 | ||
942 | <para> | |
943 | In return, the allocated record can be accessed as | |
944 | ||
945 | <informalexample> | |
946 | <programlisting> | |
947 | <![CDATA[ | |
437a5a46 | 948 | struct mychip *chip = card->private_data; |
1da177e4 LT |
949 | ]]> |
950 | </programlisting> | |
951 | </informalexample> | |
952 | ||
953 | With this method, you don't have to allocate twice. | |
954 | The record is released together with the card instance. | |
955 | </para> | |
956 | </section> | |
957 | ||
958 | <section id="card-management-chip-specific-allocate-extra"> | |
959 | <title>2. Allocating an extra device.</title> | |
960 | ||
961 | <para> | |
962 | After allocating a card instance via | |
393aa9c1 | 963 | <function>snd_card_new()</function> (with |
d453379b | 964 | <constant>0</constant> on the 4th arg), call |
561b220a | 965 | <function>kzalloc()</function>. |
1da177e4 LT |
966 | |
967 | <informalexample> | |
968 | <programlisting> | |
969 | <![CDATA[ | |
446ab5f5 TI |
970 | struct snd_card *card; |
971 | struct mychip *chip; | |
393aa9c1 TI |
972 | err = snd_card_new(&pci->dev, index[dev], id[dev], THIS_MODULE, |
973 | 0, &card); | |
1da177e4 | 974 | ..... |
561b220a | 975 | chip = kzalloc(sizeof(*chip), GFP_KERNEL); |
1da177e4 LT |
976 | ]]> |
977 | </programlisting> | |
978 | </informalexample> | |
979 | </para> | |
980 | ||
981 | <para> | |
982 | The chip record should have the field to hold the card | |
983 | pointer at least, | |
984 | ||
985 | <informalexample> | |
986 | <programlisting> | |
987 | <![CDATA[ | |
446ab5f5 TI |
988 | struct mychip { |
989 | struct snd_card *card; | |
1da177e4 LT |
990 | .... |
991 | }; | |
992 | ]]> | |
993 | </programlisting> | |
994 | </informalexample> | |
995 | </para> | |
996 | ||
997 | <para> | |
998 | Then, set the card pointer in the returned chip instance. | |
999 | ||
1000 | <informalexample> | |
1001 | <programlisting> | |
1002 | <![CDATA[ | |
1003 | chip->card = card; | |
1004 | ]]> | |
1005 | </programlisting> | |
1006 | </informalexample> | |
1007 | </para> | |
1008 | ||
1009 | <para> | |
1010 | Next, initialize the fields, and register this chip | |
1011 | record as a low-level device with a specified | |
1012 | <parameter>ops</parameter>, | |
1013 | ||
1014 | <informalexample> | |
1015 | <programlisting> | |
1016 | <![CDATA[ | |
446ab5f5 | 1017 | static struct snd_device_ops ops = { |
1da177e4 LT |
1018 | .dev_free = snd_mychip_dev_free, |
1019 | }; | |
1020 | .... | |
1021 | snd_device_new(card, SNDRV_DEV_LOWLEVEL, chip, &ops); | |
1022 | ]]> | |
1023 | </programlisting> | |
1024 | </informalexample> | |
1025 | ||
1026 | <function>snd_mychip_dev_free()</function> is the | |
1027 | device-destructor function, which will call the real | |
1028 | destructor. | |
1029 | </para> | |
1030 | ||
1031 | <para> | |
1032 | <informalexample> | |
1033 | <programlisting> | |
1034 | <![CDATA[ | |
446ab5f5 | 1035 | static int snd_mychip_dev_free(struct snd_device *device) |
1da177e4 | 1036 | { |
446ab5f5 | 1037 | return snd_mychip_free(device->device_data); |
1da177e4 LT |
1038 | } |
1039 | ]]> | |
1040 | </programlisting> | |
1041 | </informalexample> | |
1042 | ||
1043 | where <function>snd_mychip_free()</function> is the real destructor. | |
1044 | </para> | |
1045 | </section> | |
1046 | </section> | |
1047 | ||
1048 | <section id="card-management-registration"> | |
1049 | <title>Registration and Release</title> | |
1050 | <para> | |
1051 | After all components are assigned, register the card instance | |
3f03f7c5 MO |
1052 | by calling <function>snd_card_register()</function>. Access |
1053 | to the device files is enabled at this point. That is, before | |
1da177e4 LT |
1054 | <function>snd_card_register()</function> is called, the |
1055 | components are safely inaccessible from external side. If this | |
1056 | call fails, exit the probe function after releasing the card via | |
1057 | <function>snd_card_free()</function>. | |
1058 | </para> | |
1059 | ||
1060 | <para> | |
1061 | For releasing the card instance, you can call simply | |
3f03f7c5 | 1062 | <function>snd_card_free()</function>. As mentioned earlier, all |
1da177e4 LT |
1063 | components are released automatically by this call. |
1064 | </para> | |
1065 | ||
1da177e4 LT |
1066 | <para> |
1067 | For a device which allows hotplugging, you can use | |
2b29b13c TI |
1068 | <function>snd_card_free_when_closed</function>. This one will |
1069 | postpone the destruction until all devices are closed. | |
1da177e4 LT |
1070 | </para> |
1071 | ||
1072 | </section> | |
1073 | ||
1074 | </chapter> | |
1075 | ||
1076 | ||
1077 | <!-- ****************************************************** --> | |
3f03f7c5 | 1078 | <!-- PCI Resource Management --> |
1da177e4 LT |
1079 | <!-- ****************************************************** --> |
1080 | <chapter id="pci-resource"> | |
3f03f7c5 | 1081 | <title>PCI Resource Management</title> |
1da177e4 LT |
1082 | |
1083 | <section id="pci-resource-example"> | |
1084 | <title>Full Code Example</title> | |
1085 | <para> | |
3f03f7c5 MO |
1086 | In this section, we'll complete the chip-specific constructor, |
1087 | destructor and PCI entries. Example code is shown first, | |
1da177e4 LT |
1088 | below. |
1089 | ||
1090 | <example> | |
3f03f7c5 | 1091 | <title>PCI Resource Management Example</title> |
1da177e4 LT |
1092 | <programlisting> |
1093 | <![CDATA[ | |
446ab5f5 TI |
1094 | struct mychip { |
1095 | struct snd_card *card; | |
1da177e4 LT |
1096 | struct pci_dev *pci; |
1097 | ||
1098 | unsigned long port; | |
1099 | int irq; | |
1100 | }; | |
1101 | ||
446ab5f5 | 1102 | static int snd_mychip_free(struct mychip *chip) |
1da177e4 LT |
1103 | { |
1104 | /* disable hardware here if any */ | |
95a5b085 | 1105 | .... /* (not implemented in this document) */ |
1da177e4 LT |
1106 | |
1107 | /* release the irq */ | |
1108 | if (chip->irq >= 0) | |
437a5a46 | 1109 | free_irq(chip->irq, chip); |
3f03f7c5 | 1110 | /* release the I/O ports & memory */ |
1da177e4 LT |
1111 | pci_release_regions(chip->pci); |
1112 | /* disable the PCI entry */ | |
1113 | pci_disable_device(chip->pci); | |
1114 | /* release the data */ | |
1115 | kfree(chip); | |
1116 | return 0; | |
1117 | } | |
1118 | ||
1119 | /* chip-specific constructor */ | |
090015ae TI |
1120 | static int snd_mychip_create(struct snd_card *card, |
1121 | struct pci_dev *pci, | |
1122 | struct mychip **rchip) | |
1da177e4 | 1123 | { |
446ab5f5 | 1124 | struct mychip *chip; |
1da177e4 | 1125 | int err; |
446ab5f5 | 1126 | static struct snd_device_ops ops = { |
1da177e4 LT |
1127 | .dev_free = snd_mychip_dev_free, |
1128 | }; | |
1129 | ||
1130 | *rchip = NULL; | |
1131 | ||
1132 | /* initialize the PCI entry */ | |
95a5b085 TI |
1133 | err = pci_enable_device(pci); |
1134 | if (err < 0) | |
1da177e4 LT |
1135 | return err; |
1136 | /* check PCI availability (28bit DMA) */ | |
2c5510d4 YH |
1137 | if (pci_set_dma_mask(pci, DMA_BIT_MASK(28)) < 0 || |
1138 | pci_set_consistent_dma_mask(pci, DMA_BIT_MASK(28)) < 0) { | |
1da177e4 LT |
1139 | printk(KERN_ERR "error to set 28bit mask DMA\n"); |
1140 | pci_disable_device(pci); | |
1141 | return -ENXIO; | |
1142 | } | |
1143 | ||
561b220a | 1144 | chip = kzalloc(sizeof(*chip), GFP_KERNEL); |
1da177e4 LT |
1145 | if (chip == NULL) { |
1146 | pci_disable_device(pci); | |
1147 | return -ENOMEM; | |
1148 | } | |
1149 | ||
1150 | /* initialize the stuff */ | |
1151 | chip->card = card; | |
1152 | chip->pci = pci; | |
1153 | chip->irq = -1; | |
1154 | ||
1155 | /* (1) PCI resource allocation */ | |
95a5b085 TI |
1156 | err = pci_request_regions(pci, "My Chip"); |
1157 | if (err < 0) { | |
1da177e4 LT |
1158 | kfree(chip); |
1159 | pci_disable_device(pci); | |
1160 | return err; | |
1161 | } | |
1162 | chip->port = pci_resource_start(pci, 0); | |
1163 | if (request_irq(pci->irq, snd_mychip_interrupt, | |
ce1fd369 | 1164 | IRQF_SHARED, KBUILD_MODNAME, chip)) { |
1da177e4 LT |
1165 | printk(KERN_ERR "cannot grab irq %d\n", pci->irq); |
1166 | snd_mychip_free(chip); | |
1167 | return -EBUSY; | |
1168 | } | |
1169 | chip->irq = pci->irq; | |
1170 | ||
1171 | /* (2) initialization of the chip hardware */ | |
95a5b085 | 1172 | .... /* (not implemented in this document) */ |
1da177e4 | 1173 | |
95a5b085 TI |
1174 | err = snd_device_new(card, SNDRV_DEV_LOWLEVEL, chip, &ops); |
1175 | if (err < 0) { | |
1da177e4 LT |
1176 | snd_mychip_free(chip); |
1177 | return err; | |
1178 | } | |
1179 | ||
1da177e4 LT |
1180 | *rchip = chip; |
1181 | return 0; | |
1182 | } | |
1183 | ||
1184 | /* PCI IDs */ | |
f40b6890 | 1185 | static struct pci_device_id snd_mychip_ids[] = { |
1da177e4 LT |
1186 | { PCI_VENDOR_ID_FOO, PCI_DEVICE_ID_BAR, |
1187 | PCI_ANY_ID, PCI_ANY_ID, 0, 0, 0, }, | |
1188 | .... | |
1189 | { 0, } | |
1190 | }; | |
1191 | MODULE_DEVICE_TABLE(pci, snd_mychip_ids); | |
1192 | ||
1193 | /* pci_driver definition */ | |
1194 | static struct pci_driver driver = { | |
ce1fd369 | 1195 | .name = KBUILD_MODNAME, |
1da177e4 LT |
1196 | .id_table = snd_mychip_ids, |
1197 | .probe = snd_mychip_probe, | |
090015ae | 1198 | .remove = snd_mychip_remove, |
1da177e4 LT |
1199 | }; |
1200 | ||
3f03f7c5 | 1201 | /* module initialization */ |
1da177e4 LT |
1202 | static int __init alsa_card_mychip_init(void) |
1203 | { | |
01d25d46 | 1204 | return pci_register_driver(&driver); |
1da177e4 LT |
1205 | } |
1206 | ||
3f03f7c5 | 1207 | /* module clean up */ |
1da177e4 LT |
1208 | static void __exit alsa_card_mychip_exit(void) |
1209 | { | |
1210 | pci_unregister_driver(&driver); | |
1211 | } | |
1212 | ||
1213 | module_init(alsa_card_mychip_init) | |
1214 | module_exit(alsa_card_mychip_exit) | |
1215 | ||
1216 | EXPORT_NO_SYMBOLS; /* for old kernels only */ | |
1217 | ]]> | |
1218 | </programlisting> | |
1219 | </example> | |
1220 | </para> | |
1221 | </section> | |
1222 | ||
1223 | <section id="pci-resource-some-haftas"> | |
1224 | <title>Some Hafta's</title> | |
1225 | <para> | |
1226 | The allocation of PCI resources is done in the | |
1227 | <function>probe()</function> function, and usually an extra | |
1228 | <function>xxx_create()</function> function is written for this | |
56b146d3 | 1229 | purpose. |
1da177e4 LT |
1230 | </para> |
1231 | ||
1232 | <para> | |
3f03f7c5 MO |
1233 | In the case of PCI devices, you first have to call |
1234 | the <function>pci_enable_device()</function> function before | |
1da177e4 | 1235 | allocating resources. Also, you need to set the proper PCI DMA |
3f03f7c5 | 1236 | mask to limit the accessed I/O range. In some cases, you might |
1da177e4 | 1237 | need to call <function>pci_set_master()</function> function, |
56b146d3 | 1238 | too. |
1da177e4 LT |
1239 | </para> |
1240 | ||
1241 | <para> | |
1242 | Suppose the 28bit mask, and the code to be added would be like: | |
1243 | ||
1244 | <informalexample> | |
1245 | <programlisting> | |
1246 | <![CDATA[ | |
95a5b085 TI |
1247 | err = pci_enable_device(pci); |
1248 | if (err < 0) | |
1da177e4 | 1249 | return err; |
2c5510d4 YH |
1250 | if (pci_set_dma_mask(pci, DMA_BIT_MASK(28)) < 0 || |
1251 | pci_set_consistent_dma_mask(pci, DMA_BIT_MASK(28)) < 0) { | |
1da177e4 LT |
1252 | printk(KERN_ERR "error to set 28bit mask DMA\n"); |
1253 | pci_disable_device(pci); | |
1254 | return -ENXIO; | |
1255 | } | |
1256 | ||
1257 | ]]> | |
1258 | </programlisting> | |
1259 | </informalexample> | |
1260 | </para> | |
1261 | </section> | |
1262 | ||
1263 | <section id="pci-resource-resource-allocation"> | |
1264 | <title>Resource Allocation</title> | |
1265 | <para> | |
3f03f7c5 | 1266 | The allocation of I/O ports and irqs is done via standard kernel |
1da177e4 LT |
1267 | functions. Unlike ALSA ver.0.5.x., there are no helpers for |
1268 | that. And these resources must be released in the destructor | |
1269 | function (see below). Also, on ALSA 0.9.x, you don't need to | |
3f03f7c5 | 1270 | allocate (pseudo-)DMA for PCI like in ALSA 0.5.x. |
1da177e4 LT |
1271 | </para> |
1272 | ||
1273 | <para> | |
3f03f7c5 | 1274 | Now assume that the PCI device has an I/O port with 8 bytes |
446ab5f5 | 1275 | and an interrupt. Then struct <structname>mychip</structname> will have the |
56b146d3 | 1276 | following fields: |
1da177e4 LT |
1277 | |
1278 | <informalexample> | |
1279 | <programlisting> | |
1280 | <![CDATA[ | |
446ab5f5 TI |
1281 | struct mychip { |
1282 | struct snd_card *card; | |
1da177e4 LT |
1283 | |
1284 | unsigned long port; | |
1285 | int irq; | |
1286 | }; | |
1287 | ]]> | |
1288 | </programlisting> | |
1289 | </informalexample> | |
1290 | </para> | |
1291 | ||
1292 | <para> | |
3f03f7c5 | 1293 | For an I/O port (and also a memory region), you need to have |
1da177e4 LT |
1294 | the resource pointer for the standard resource management. For |
1295 | an irq, you have to keep only the irq number (integer). But you | |
1296 | need to initialize this number as -1 before actual allocation, | |
1297 | since irq 0 is valid. The port address and its resource pointer | |
1298 | can be initialized as null by | |
561b220a | 1299 | <function>kzalloc()</function> automatically, so you |
1da177e4 LT |
1300 | don't have to take care of resetting them. |
1301 | </para> | |
1302 | ||
1303 | <para> | |
3f03f7c5 | 1304 | The allocation of an I/O port is done like this: |
1da177e4 LT |
1305 | |
1306 | <informalexample> | |
1307 | <programlisting> | |
1308 | <![CDATA[ | |
95a5b085 TI |
1309 | err = pci_request_regions(pci, "My Chip"); |
1310 | if (err < 0) { | |
1da177e4 LT |
1311 | kfree(chip); |
1312 | pci_disable_device(pci); | |
1313 | return err; | |
1314 | } | |
1315 | chip->port = pci_resource_start(pci, 0); | |
1316 | ]]> | |
1317 | </programlisting> | |
1318 | </informalexample> | |
1319 | </para> | |
1320 | ||
1321 | <para> | |
1322 | <!-- obsolete --> | |
3f03f7c5 | 1323 | It will reserve the I/O port region of 8 bytes of the given |
1da177e4 LT |
1324 | PCI device. The returned value, chip->res_port, is allocated |
1325 | via <function>kmalloc()</function> by | |
1326 | <function>request_region()</function>. The pointer must be | |
3f03f7c5 MO |
1327 | released via <function>kfree()</function>, but there is a |
1328 | problem with this. This issue will be explained later. | |
1da177e4 LT |
1329 | </para> |
1330 | ||
1331 | <para> | |
1332 | The allocation of an interrupt source is done like this: | |
1333 | ||
1334 | <informalexample> | |
1335 | <programlisting> | |
1336 | <![CDATA[ | |
1337 | if (request_irq(pci->irq, snd_mychip_interrupt, | |
ce1fd369 | 1338 | IRQF_SHARED, KBUILD_MODNAME, chip)) { |
1da177e4 LT |
1339 | printk(KERN_ERR "cannot grab irq %d\n", pci->irq); |
1340 | snd_mychip_free(chip); | |
1341 | return -EBUSY; | |
1342 | } | |
1343 | chip->irq = pci->irq; | |
1344 | ]]> | |
1345 | </programlisting> | |
1346 | </informalexample> | |
1347 | ||
1348 | where <function>snd_mychip_interrupt()</function> is the | |
1349 | interrupt handler defined <link | |
1350 | linkend="pcm-interface-interrupt-handler"><citetitle>later</citetitle></link>. | |
1351 | Note that chip->irq should be defined | |
1352 | only when <function>request_irq()</function> succeeded. | |
1353 | </para> | |
1354 | ||
1355 | <para> | |
3f03f7c5 MO |
1356 | On the PCI bus, interrupts can be shared. Thus, |
1357 | <constant>IRQF_SHARED</constant> is used as the interrupt flag of | |
1da177e4 LT |
1358 | <function>request_irq()</function>. |
1359 | </para> | |
1360 | ||
1361 | <para> | |
1362 | The last argument of <function>request_irq()</function> is the | |
1363 | data pointer passed to the interrupt handler. Usually, the | |
1364 | chip-specific record is used for that, but you can use what you | |
1365 | like, too. | |
1366 | </para> | |
1367 | ||
1368 | <para> | |
3f03f7c5 | 1369 | I won't give details about the interrupt handler at this |
1da177e4 LT |
1370 | point, but at least its appearance can be explained now. The |
1371 | interrupt handler looks usually like the following: | |
1372 | ||
1373 | <informalexample> | |
1374 | <programlisting> | |
1375 | <![CDATA[ | |
ad4d1dea | 1376 | static irqreturn_t snd_mychip_interrupt(int irq, void *dev_id) |
1da177e4 | 1377 | { |
446ab5f5 | 1378 | struct mychip *chip = dev_id; |
1da177e4 LT |
1379 | .... |
1380 | return IRQ_HANDLED; | |
1381 | } | |
1382 | ]]> | |
1383 | </programlisting> | |
1384 | </informalexample> | |
1385 | </para> | |
1386 | ||
1387 | <para> | |
1388 | Now let's write the corresponding destructor for the resources | |
1389 | above. The role of destructor is simple: disable the hardware | |
1390 | (if already activated) and release the resources. So far, we | |
3f03f7c5 | 1391 | have no hardware part, so the disabling code is not written here. |
1da177e4 LT |
1392 | </para> |
1393 | ||
1394 | <para> | |
3f03f7c5 | 1395 | To release the resources, the <quote>check-and-release</quote> |
1da177e4 LT |
1396 | method is a safer way. For the interrupt, do like this: |
1397 | ||
1398 | <informalexample> | |
1399 | <programlisting> | |
1400 | <![CDATA[ | |
1401 | if (chip->irq >= 0) | |
437a5a46 | 1402 | free_irq(chip->irq, chip); |
1da177e4 LT |
1403 | ]]> |
1404 | </programlisting> | |
1405 | </informalexample> | |
1406 | ||
1407 | Since the irq number can start from 0, you should initialize | |
1408 | chip->irq with a negative value (e.g. -1), so that you can | |
1409 | check the validity of the irq number as above. | |
1410 | </para> | |
1411 | ||
1412 | <para> | |
1413 | When you requested I/O ports or memory regions via | |
1414 | <function>pci_request_region()</function> or | |
3f03f7c5 | 1415 | <function>pci_request_regions()</function> like in this example, |
1da177e4 LT |
1416 | release the resource(s) using the corresponding function, |
1417 | <function>pci_release_region()</function> or | |
1418 | <function>pci_release_regions()</function>. | |
1419 | ||
1420 | <informalexample> | |
1421 | <programlisting> | |
1422 | <![CDATA[ | |
1423 | pci_release_regions(chip->pci); | |
1424 | ]]> | |
1425 | </programlisting> | |
1426 | </informalexample> | |
1427 | </para> | |
1428 | ||
1429 | <para> | |
1430 | When you requested manually via <function>request_region()</function> | |
1431 | or <function>request_mem_region</function>, you can release it via | |
1432 | <function>release_resource()</function>. Suppose that you keep | |
1433 | the resource pointer returned from <function>request_region()</function> | |
3f03f7c5 | 1434 | in chip->res_port, the release procedure looks like: |
1da177e4 LT |
1435 | |
1436 | <informalexample> | |
1437 | <programlisting> | |
1438 | <![CDATA[ | |
b1d5776d | 1439 | release_and_free_resource(chip->res_port); |
1da177e4 LT |
1440 | ]]> |
1441 | </programlisting> | |
1442 | </informalexample> | |
1da177e4 LT |
1443 | </para> |
1444 | ||
1445 | <para> | |
1446 | Don't forget to call <function>pci_disable_device()</function> | |
3f03f7c5 | 1447 | before the end. |
1da177e4 LT |
1448 | </para> |
1449 | ||
1450 | <para> | |
1451 | And finally, release the chip-specific record. | |
1452 | ||
1453 | <informalexample> | |
1454 | <programlisting> | |
1455 | <![CDATA[ | |
1456 | kfree(chip); | |
1457 | ]]> | |
1458 | </programlisting> | |
1459 | </informalexample> | |
1460 | </para> | |
1461 | ||
1da177e4 | 1462 | <para> |
3f03f7c5 | 1463 | We didn't implement the hardware disabling part in the above. |
1da177e4 LT |
1464 | If you need to do this, please note that the destructor may be |
1465 | called even before the initialization of the chip is completed. | |
3f03f7c5 | 1466 | It would be better to have a flag to skip hardware disabling |
1da177e4 LT |
1467 | if the hardware was not initialized yet. |
1468 | </para> | |
1469 | ||
1470 | <para> | |
1471 | When the chip-data is assigned to the card using | |
1472 | <function>snd_device_new()</function> with | |
1473 | <constant>SNDRV_DEV_LOWLELVEL</constant> , its destructor is | |
1474 | called at the last. That is, it is assured that all other | |
3f03f7c5 MO |
1475 | components like PCMs and controls have already been released. |
1476 | You don't have to stop PCMs, etc. explicitly, but just | |
1477 | call low-level hardware stopping. | |
1da177e4 LT |
1478 | </para> |
1479 | ||
1480 | <para> | |
1481 | The management of a memory-mapped region is almost as same as | |
3f03f7c5 | 1482 | the management of an I/O port. You'll need three fields like |
1da177e4 LT |
1483 | the following: |
1484 | ||
1485 | <informalexample> | |
1486 | <programlisting> | |
1487 | <![CDATA[ | |
446ab5f5 | 1488 | struct mychip { |
1da177e4 LT |
1489 | .... |
1490 | unsigned long iobase_phys; | |
1491 | void __iomem *iobase_virt; | |
1492 | }; | |
1493 | ]]> | |
1494 | </programlisting> | |
1495 | </informalexample> | |
1496 | ||
1497 | and the allocation would be like below: | |
1498 | ||
1499 | <informalexample> | |
1500 | <programlisting> | |
1501 | <![CDATA[ | |
1502 | if ((err = pci_request_regions(pci, "My Chip")) < 0) { | |
1503 | kfree(chip); | |
1504 | return err; | |
1505 | } | |
1506 | chip->iobase_phys = pci_resource_start(pci, 0); | |
1507 | chip->iobase_virt = ioremap_nocache(chip->iobase_phys, | |
1508 | pci_resource_len(pci, 0)); | |
1509 | ]]> | |
1510 | </programlisting> | |
1511 | </informalexample> | |
1512 | ||
1513 | and the corresponding destructor would be: | |
1514 | ||
1515 | <informalexample> | |
1516 | <programlisting> | |
1517 | <![CDATA[ | |
446ab5f5 | 1518 | static int snd_mychip_free(struct mychip *chip) |
1da177e4 LT |
1519 | { |
1520 | .... | |
1521 | if (chip->iobase_virt) | |
1522 | iounmap(chip->iobase_virt); | |
1523 | .... | |
1524 | pci_release_regions(chip->pci); | |
1525 | .... | |
1526 | } | |
1527 | ]]> | |
1528 | </programlisting> | |
1529 | </informalexample> | |
1530 | </para> | |
1531 | ||
1532 | </section> | |
1533 | ||
1da177e4 LT |
1534 | <section id="pci-resource-entries"> |
1535 | <title>PCI Entries</title> | |
1536 | <para> | |
3f03f7c5 MO |
1537 | So far, so good. Let's finish the missing PCI |
1538 | stuff. At first, we need a | |
1da177e4 LT |
1539 | <structname>pci_device_id</structname> table for this |
1540 | chipset. It's a table of PCI vendor/device ID number, and some | |
1541 | masks. | |
1542 | </para> | |
1543 | ||
1544 | <para> | |
1545 | For example, | |
1546 | ||
1547 | <informalexample> | |
1548 | <programlisting> | |
1549 | <![CDATA[ | |
f40b6890 | 1550 | static struct pci_device_id snd_mychip_ids[] = { |
1da177e4 LT |
1551 | { PCI_VENDOR_ID_FOO, PCI_DEVICE_ID_BAR, |
1552 | PCI_ANY_ID, PCI_ANY_ID, 0, 0, 0, }, | |
1553 | .... | |
1554 | { 0, } | |
1555 | }; | |
1556 | MODULE_DEVICE_TABLE(pci, snd_mychip_ids); | |
1557 | ]]> | |
1558 | </programlisting> | |
1559 | </informalexample> | |
1560 | </para> | |
1561 | ||
1562 | <para> | |
1563 | The first and second fields of | |
3f03f7c5 MO |
1564 | the <structname>pci_device_id</structname> structure are the vendor and |
1565 | device IDs. If you have no reason to filter the matching | |
1566 | devices, you can leave the remaining fields as above. The last | |
1567 | field of the <structname>pci_device_id</structname> struct contains | |
1da177e4 | 1568 | private data for this entry. You can specify any value here, for |
3f03f7c5 MO |
1569 | example, to define specific operations for supported device IDs. |
1570 | Such an example is found in the intel8x0 driver. | |
1da177e4 LT |
1571 | </para> |
1572 | ||
1573 | <para> | |
1574 | The last entry of this list is the terminator. You must | |
1575 | specify this all-zero entry. | |
1576 | </para> | |
1577 | ||
1578 | <para> | |
1579 | Then, prepare the <structname>pci_driver</structname> record: | |
1580 | ||
1581 | <informalexample> | |
1582 | <programlisting> | |
1583 | <![CDATA[ | |
1584 | static struct pci_driver driver = { | |
ce1fd369 | 1585 | .name = KBUILD_MODNAME, |
1da177e4 LT |
1586 | .id_table = snd_mychip_ids, |
1587 | .probe = snd_mychip_probe, | |
090015ae | 1588 | .remove = snd_mychip_remove, |
1da177e4 LT |
1589 | }; |
1590 | ]]> | |
1591 | </programlisting> | |
1592 | </informalexample> | |
1593 | </para> | |
1594 | ||
1595 | <para> | |
1596 | The <structfield>probe</structfield> and | |
3f03f7c5 MO |
1597 | <structfield>remove</structfield> functions have already |
1598 | been defined in the previous sections. | |
090015ae | 1599 | The <structfield>name</structfield> |
1da177e4 LT |
1600 | field is the name string of this device. Note that you must not |
1601 | use a slash <quote>/</quote> in this string. | |
1602 | </para> | |
1603 | ||
1604 | <para> | |
1605 | And at last, the module entries: | |
1606 | ||
1607 | <informalexample> | |
1608 | <programlisting> | |
1609 | <![CDATA[ | |
1610 | static int __init alsa_card_mychip_init(void) | |
1611 | { | |
01d25d46 | 1612 | return pci_register_driver(&driver); |
1da177e4 LT |
1613 | } |
1614 | ||
1615 | static void __exit alsa_card_mychip_exit(void) | |
1616 | { | |
1617 | pci_unregister_driver(&driver); | |
1618 | } | |
1619 | ||
1620 | module_init(alsa_card_mychip_init) | |
1621 | module_exit(alsa_card_mychip_exit) | |
1622 | ]]> | |
1623 | </programlisting> | |
1624 | </informalexample> | |
1625 | </para> | |
1626 | ||
1627 | <para> | |
1628 | Note that these module entries are tagged with | |
1629 | <parameter>__init</parameter> and | |
090015ae | 1630 | <parameter>__exit</parameter> prefixes. |
1da177e4 LT |
1631 | </para> |
1632 | ||
1633 | <para> | |
1634 | Oh, one thing was forgotten. If you have no exported symbols, | |
3f03f7c5 | 1635 | you need to declare it in 2.2 or 2.4 kernels (it's not necessary in 2.6 kernels). |
1da177e4 LT |
1636 | |
1637 | <informalexample> | |
1638 | <programlisting> | |
1639 | <![CDATA[ | |
1640 | EXPORT_NO_SYMBOLS; | |
1641 | ]]> | |
1642 | </programlisting> | |
1643 | </informalexample> | |
1644 | ||
1645 | That's all! | |
1646 | </para> | |
1647 | </section> | |
1648 | </chapter> | |
1649 | ||
1650 | ||
1651 | <!-- ****************************************************** --> | |
1652 | <!-- PCM Interface --> | |
1653 | <!-- ****************************************************** --> | |
1654 | <chapter id="pcm-interface"> | |
1655 | <title>PCM Interface</title> | |
1656 | ||
1657 | <section id="pcm-interface-general"> | |
1658 | <title>General</title> | |
1659 | <para> | |
1660 | The PCM middle layer of ALSA is quite powerful and it is only | |
1661 | necessary for each driver to implement the low-level functions | |
1662 | to access its hardware. | |
1663 | </para> | |
1664 | ||
1665 | <para> | |
1666 | For accessing to the PCM layer, you need to include | |
3f03f7c5 | 1667 | <filename><sound/pcm.h></filename> first. In addition, |
1da177e4 LT |
1668 | <filename><sound/pcm_params.h></filename> might be needed |
1669 | if you access to some functions related with hw_param. | |
1670 | </para> | |
1671 | ||
1672 | <para> | |
1673 | Each card device can have up to four pcm instances. A pcm | |
1674 | instance corresponds to a pcm device file. The limitation of | |
1675 | number of instances comes only from the available bit size of | |
3f03f7c5 MO |
1676 | the Linux's device numbers. Once when 64bit device number is |
1677 | used, we'll have more pcm instances available. | |
1da177e4 LT |
1678 | </para> |
1679 | ||
1680 | <para> | |
1681 | A pcm instance consists of pcm playback and capture streams, | |
1682 | and each pcm stream consists of one or more pcm substreams. Some | |
3f03f7c5 | 1683 | soundcards support multiple playback functions. For example, |
1da177e4 LT |
1684 | emu10k1 has a PCM playback of 32 stereo substreams. In this case, at |
1685 | each open, a free substream is (usually) automatically chosen | |
1686 | and opened. Meanwhile, when only one substream exists and it was | |
3f03f7c5 MO |
1687 | already opened, the successful open will either block |
1688 | or error with <constant>EAGAIN</constant> according to the | |
1689 | file open mode. But you don't have to care about such details in your | |
1690 | driver. The PCM middle layer will take care of such work. | |
1da177e4 LT |
1691 | </para> |
1692 | </section> | |
1693 | ||
1694 | <section id="pcm-interface-example"> | |
1695 | <title>Full Code Example</title> | |
1696 | <para> | |
1697 | The example code below does not include any hardware access | |
1698 | routines but shows only the skeleton, how to build up the PCM | |
1699 | interfaces. | |
1700 | ||
1701 | <example> | |
1702 | <title>PCM Example Code</title> | |
1703 | <programlisting> | |
1704 | <![CDATA[ | |
1705 | #include <sound/pcm.h> | |
1706 | .... | |
1707 | ||
1708 | /* hardware definition */ | |
446ab5f5 | 1709 | static struct snd_pcm_hardware snd_mychip_playback_hw = { |
1da177e4 LT |
1710 | .info = (SNDRV_PCM_INFO_MMAP | |
1711 | SNDRV_PCM_INFO_INTERLEAVED | | |
1712 | SNDRV_PCM_INFO_BLOCK_TRANSFER | | |
1713 | SNDRV_PCM_INFO_MMAP_VALID), | |
1714 | .formats = SNDRV_PCM_FMTBIT_S16_LE, | |
1715 | .rates = SNDRV_PCM_RATE_8000_48000, | |
1716 | .rate_min = 8000, | |
1717 | .rate_max = 48000, | |
1718 | .channels_min = 2, | |
1719 | .channels_max = 2, | |
1720 | .buffer_bytes_max = 32768, | |
1721 | .period_bytes_min = 4096, | |
1722 | .period_bytes_max = 32768, | |
1723 | .periods_min = 1, | |
1724 | .periods_max = 1024, | |
1725 | }; | |
1726 | ||
1727 | /* hardware definition */ | |
446ab5f5 | 1728 | static struct snd_pcm_hardware snd_mychip_capture_hw = { |
1da177e4 LT |
1729 | .info = (SNDRV_PCM_INFO_MMAP | |
1730 | SNDRV_PCM_INFO_INTERLEAVED | | |
1731 | SNDRV_PCM_INFO_BLOCK_TRANSFER | | |
1732 | SNDRV_PCM_INFO_MMAP_VALID), | |
1733 | .formats = SNDRV_PCM_FMTBIT_S16_LE, | |
1734 | .rates = SNDRV_PCM_RATE_8000_48000, | |
1735 | .rate_min = 8000, | |
1736 | .rate_max = 48000, | |
1737 | .channels_min = 2, | |
1738 | .channels_max = 2, | |
1739 | .buffer_bytes_max = 32768, | |
1740 | .period_bytes_min = 4096, | |
1741 | .period_bytes_max = 32768, | |
1742 | .periods_min = 1, | |
1743 | .periods_max = 1024, | |
1744 | }; | |
1745 | ||
1746 | /* open callback */ | |
446ab5f5 | 1747 | static int snd_mychip_playback_open(struct snd_pcm_substream *substream) |
1da177e4 | 1748 | { |
446ab5f5 TI |
1749 | struct mychip *chip = snd_pcm_substream_chip(substream); |
1750 | struct snd_pcm_runtime *runtime = substream->runtime; | |
1da177e4 LT |
1751 | |
1752 | runtime->hw = snd_mychip_playback_hw; | |
95a5b085 TI |
1753 | /* more hardware-initialization will be done here */ |
1754 | .... | |
1da177e4 LT |
1755 | return 0; |
1756 | } | |
1757 | ||
1758 | /* close callback */ | |
446ab5f5 | 1759 | static int snd_mychip_playback_close(struct snd_pcm_substream *substream) |
1da177e4 | 1760 | { |
446ab5f5 | 1761 | struct mychip *chip = snd_pcm_substream_chip(substream); |
95a5b085 TI |
1762 | /* the hardware-specific codes will be here */ |
1763 | .... | |
1da177e4 LT |
1764 | return 0; |
1765 | ||
1766 | } | |
1767 | ||
1768 | /* open callback */ | |
446ab5f5 | 1769 | static int snd_mychip_capture_open(struct snd_pcm_substream *substream) |
1da177e4 | 1770 | { |
446ab5f5 TI |
1771 | struct mychip *chip = snd_pcm_substream_chip(substream); |
1772 | struct snd_pcm_runtime *runtime = substream->runtime; | |
1da177e4 LT |
1773 | |
1774 | runtime->hw = snd_mychip_capture_hw; | |
95a5b085 TI |
1775 | /* more hardware-initialization will be done here */ |
1776 | .... | |
1da177e4 LT |
1777 | return 0; |
1778 | } | |
1779 | ||
1780 | /* close callback */ | |
446ab5f5 | 1781 | static int snd_mychip_capture_close(struct snd_pcm_substream *substream) |
1da177e4 | 1782 | { |
446ab5f5 | 1783 | struct mychip *chip = snd_pcm_substream_chip(substream); |
95a5b085 TI |
1784 | /* the hardware-specific codes will be here */ |
1785 | .... | |
1da177e4 LT |
1786 | return 0; |
1787 | ||
1788 | } | |
1789 | ||
1790 | /* hw_params callback */ | |
446ab5f5 TI |
1791 | static int snd_mychip_pcm_hw_params(struct snd_pcm_substream *substream, |
1792 | struct snd_pcm_hw_params *hw_params) | |
1da177e4 LT |
1793 | { |
1794 | return snd_pcm_lib_malloc_pages(substream, | |
1795 | params_buffer_bytes(hw_params)); | |
1796 | } | |
1797 | ||
1798 | /* hw_free callback */ | |
446ab5f5 | 1799 | static int snd_mychip_pcm_hw_free(struct snd_pcm_substream *substream) |
1da177e4 LT |
1800 | { |
1801 | return snd_pcm_lib_free_pages(substream); | |
1802 | } | |
1803 | ||
1804 | /* prepare callback */ | |
446ab5f5 | 1805 | static int snd_mychip_pcm_prepare(struct snd_pcm_substream *substream) |
1da177e4 | 1806 | { |
446ab5f5 TI |
1807 | struct mychip *chip = snd_pcm_substream_chip(substream); |
1808 | struct snd_pcm_runtime *runtime = substream->runtime; | |
1da177e4 LT |
1809 | |
1810 | /* set up the hardware with the current configuration | |
1811 | * for example... | |
1812 | */ | |
1813 | mychip_set_sample_format(chip, runtime->format); | |
1814 | mychip_set_sample_rate(chip, runtime->rate); | |
1815 | mychip_set_channels(chip, runtime->channels); | |
0b7bed4e | 1816 | mychip_set_dma_setup(chip, runtime->dma_addr, |
1da177e4 LT |
1817 | chip->buffer_size, |
1818 | chip->period_size); | |
1819 | return 0; | |
1820 | } | |
1821 | ||
1822 | /* trigger callback */ | |
446ab5f5 | 1823 | static int snd_mychip_pcm_trigger(struct snd_pcm_substream *substream, |
1da177e4 LT |
1824 | int cmd) |
1825 | { | |
1826 | switch (cmd) { | |
1827 | case SNDRV_PCM_TRIGGER_START: | |
95a5b085 TI |
1828 | /* do something to start the PCM engine */ |
1829 | .... | |
1da177e4 LT |
1830 | break; |
1831 | case SNDRV_PCM_TRIGGER_STOP: | |
95a5b085 TI |
1832 | /* do something to stop the PCM engine */ |
1833 | .... | |
1da177e4 LT |
1834 | break; |
1835 | default: | |
1836 | return -EINVAL; | |
1837 | } | |
1838 | } | |
1839 | ||
1840 | /* pointer callback */ | |
1841 | static snd_pcm_uframes_t | |
446ab5f5 | 1842 | snd_mychip_pcm_pointer(struct snd_pcm_substream *substream) |
1da177e4 | 1843 | { |
446ab5f5 | 1844 | struct mychip *chip = snd_pcm_substream_chip(substream); |
1da177e4 LT |
1845 | unsigned int current_ptr; |
1846 | ||
1847 | /* get the current hardware pointer */ | |
1848 | current_ptr = mychip_get_hw_pointer(chip); | |
1849 | return current_ptr; | |
1850 | } | |
1851 | ||
1852 | /* operators */ | |
446ab5f5 | 1853 | static struct snd_pcm_ops snd_mychip_playback_ops = { |
1da177e4 LT |
1854 | .open = snd_mychip_playback_open, |
1855 | .close = snd_mychip_playback_close, | |
1856 | .ioctl = snd_pcm_lib_ioctl, | |
1857 | .hw_params = snd_mychip_pcm_hw_params, | |
1858 | .hw_free = snd_mychip_pcm_hw_free, | |
1859 | .prepare = snd_mychip_pcm_prepare, | |
1860 | .trigger = snd_mychip_pcm_trigger, | |
1861 | .pointer = snd_mychip_pcm_pointer, | |
1862 | }; | |
1863 | ||
1864 | /* operators */ | |
446ab5f5 | 1865 | static struct snd_pcm_ops snd_mychip_capture_ops = { |
1da177e4 LT |
1866 | .open = snd_mychip_capture_open, |
1867 | .close = snd_mychip_capture_close, | |
1868 | .ioctl = snd_pcm_lib_ioctl, | |
1869 | .hw_params = snd_mychip_pcm_hw_params, | |
1870 | .hw_free = snd_mychip_pcm_hw_free, | |
1871 | .prepare = snd_mychip_pcm_prepare, | |
1872 | .trigger = snd_mychip_pcm_trigger, | |
1873 | .pointer = snd_mychip_pcm_pointer, | |
1874 | }; | |
1875 | ||
1876 | /* | |
1877 | * definitions of capture are omitted here... | |
1878 | */ | |
1879 | ||
1880 | /* create a pcm device */ | |
090015ae | 1881 | static int snd_mychip_new_pcm(struct mychip *chip) |
1da177e4 | 1882 | { |
446ab5f5 | 1883 | struct snd_pcm *pcm; |
1da177e4 LT |
1884 | int err; |
1885 | ||
95a5b085 TI |
1886 | err = snd_pcm_new(chip->card, "My Chip", 0, 1, 1, &pcm); |
1887 | if (err < 0) | |
1da177e4 LT |
1888 | return err; |
1889 | pcm->private_data = chip; | |
1890 | strcpy(pcm->name, "My Chip"); | |
1891 | chip->pcm = pcm; | |
1892 | /* set operators */ | |
1893 | snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_PLAYBACK, | |
1894 | &snd_mychip_playback_ops); | |
1895 | snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_CAPTURE, | |
1896 | &snd_mychip_capture_ops); | |
1897 | /* pre-allocation of buffers */ | |
1898 | /* NOTE: this may fail */ | |
1899 | snd_pcm_lib_preallocate_pages_for_all(pcm, SNDRV_DMA_TYPE_DEV, | |
1900 | snd_dma_pci_data(chip->pci), | |
1901 | 64*1024, 64*1024); | |
1902 | return 0; | |
1903 | } | |
1904 | ]]> | |
1905 | </programlisting> | |
1906 | </example> | |
1907 | </para> | |
1908 | </section> | |
1909 | ||
1910 | <section id="pcm-interface-constructor"> | |
1911 | <title>Constructor</title> | |
1912 | <para> | |
3f03f7c5 | 1913 | A pcm instance is allocated by the <function>snd_pcm_new()</function> |
1da177e4 LT |
1914 | function. It would be better to create a constructor for pcm, |
1915 | namely, | |
1916 | ||
1917 | <informalexample> | |
1918 | <programlisting> | |
1919 | <![CDATA[ | |
090015ae | 1920 | static int snd_mychip_new_pcm(struct mychip *chip) |
1da177e4 | 1921 | { |
446ab5f5 | 1922 | struct snd_pcm *pcm; |
1da177e4 LT |
1923 | int err; |
1924 | ||
95a5b085 TI |
1925 | err = snd_pcm_new(chip->card, "My Chip", 0, 1, 1, &pcm); |
1926 | if (err < 0) | |
1da177e4 LT |
1927 | return err; |
1928 | pcm->private_data = chip; | |
1929 | strcpy(pcm->name, "My Chip"); | |
1930 | chip->pcm = pcm; | |
1931 | .... | |
1932 | return 0; | |
1933 | } | |
1934 | ]]> | |
1935 | </programlisting> | |
1936 | </informalexample> | |
1937 | </para> | |
1938 | ||
1939 | <para> | |
3f03f7c5 | 1940 | The <function>snd_pcm_new()</function> function takes four |
1da177e4 LT |
1941 | arguments. The first argument is the card pointer to which this |
1942 | pcm is assigned, and the second is the ID string. | |
1943 | </para> | |
1944 | ||
1945 | <para> | |
1946 | The third argument (<parameter>index</parameter>, 0 in the | |
3f03f7c5 MO |
1947 | above) is the index of this new pcm. It begins from zero. If |
1948 | you create more than one pcm instances, specify the | |
1da177e4 LT |
1949 | different numbers in this argument. For example, |
1950 | <parameter>index</parameter> = 1 for the second PCM device. | |
1951 | </para> | |
1952 | ||
1953 | <para> | |
1954 | The fourth and fifth arguments are the number of substreams | |
3f03f7c5 MO |
1955 | for playback and capture, respectively. Here 1 is used for |
1956 | both arguments. When no playback or capture substreams are available, | |
1da177e4 LT |
1957 | pass 0 to the corresponding argument. |
1958 | </para> | |
1959 | ||
1960 | <para> | |
1961 | If a chip supports multiple playbacks or captures, you can | |
1962 | specify more numbers, but they must be handled properly in | |
1963 | open/close, etc. callbacks. When you need to know which | |
1964 | substream you are referring to, then it can be obtained from | |
446ab5f5 | 1965 | struct <structname>snd_pcm_substream</structname> data passed to each callback |
1da177e4 LT |
1966 | as follows: |
1967 | ||
1968 | <informalexample> | |
1969 | <programlisting> | |
1970 | <![CDATA[ | |
446ab5f5 | 1971 | struct snd_pcm_substream *substream; |
1da177e4 LT |
1972 | int index = substream->number; |
1973 | ]]> | |
1974 | </programlisting> | |
1975 | </informalexample> | |
1976 | </para> | |
1977 | ||
1978 | <para> | |
1979 | After the pcm is created, you need to set operators for each | |
1980 | pcm stream. | |
1981 | ||
1982 | <informalexample> | |
1983 | <programlisting> | |
1984 | <![CDATA[ | |
1985 | snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_PLAYBACK, | |
1986 | &snd_mychip_playback_ops); | |
1987 | snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_CAPTURE, | |
1988 | &snd_mychip_capture_ops); | |
1989 | ]]> | |
1990 | </programlisting> | |
1991 | </informalexample> | |
1992 | </para> | |
1993 | ||
1994 | <para> | |
1995 | The operators are defined typically like this: | |
1996 | ||
1997 | <informalexample> | |
1998 | <programlisting> | |
1999 | <![CDATA[ | |
446ab5f5 | 2000 | static struct snd_pcm_ops snd_mychip_playback_ops = { |
1da177e4 LT |
2001 | .open = snd_mychip_pcm_open, |
2002 | .close = snd_mychip_pcm_close, | |
2003 | .ioctl = snd_pcm_lib_ioctl, | |
2004 | .hw_params = snd_mychip_pcm_hw_params, | |
2005 | .hw_free = snd_mychip_pcm_hw_free, | |
2006 | .prepare = snd_mychip_pcm_prepare, | |
2007 | .trigger = snd_mychip_pcm_trigger, | |
2008 | .pointer = snd_mychip_pcm_pointer, | |
2009 | }; | |
2010 | ]]> | |
2011 | </programlisting> | |
2012 | </informalexample> | |
2013 | ||
3f03f7c5 | 2014 | All the callbacks are described in the |
1da177e4 | 2015 | <link linkend="pcm-interface-operators"><citetitle> |
3f03f7c5 | 2016 | Operators</citetitle></link> subsection. |
1da177e4 LT |
2017 | </para> |
2018 | ||
2019 | <para> | |
3f03f7c5 | 2020 | After setting the operators, you probably will want to |
1da177e4 LT |
2021 | pre-allocate the buffer. For the pre-allocation, simply call |
2022 | the following: | |
2023 | ||
2024 | <informalexample> | |
2025 | <programlisting> | |
2026 | <![CDATA[ | |
2027 | snd_pcm_lib_preallocate_pages_for_all(pcm, SNDRV_DMA_TYPE_DEV, | |
2028 | snd_dma_pci_data(chip->pci), | |
2029 | 64*1024, 64*1024); | |
2030 | ]]> | |
2031 | </programlisting> | |
2032 | </informalexample> | |
2033 | ||
3f03f7c5 MO |
2034 | It will allocate a buffer up to 64kB as default. |
2035 | Buffer management details will be described in the later section <link | |
1da177e4 LT |
2036 | linkend="buffer-and-memory"><citetitle>Buffer and Memory |
2037 | Management</citetitle></link>. | |
2038 | </para> | |
2039 | ||
2040 | <para> | |
2041 | Additionally, you can set some extra information for this pcm | |
2042 | in pcm->info_flags. | |
2043 | The available values are defined as | |
2044 | <constant>SNDRV_PCM_INFO_XXX</constant> in | |
2045 | <filename><sound/asound.h></filename>, which is used for | |
2046 | the hardware definition (described later). When your soundchip | |
2047 | supports only half-duplex, specify like this: | |
2048 | ||
2049 | <informalexample> | |
2050 | <programlisting> | |
2051 | <![CDATA[ | |
2052 | pcm->info_flags = SNDRV_PCM_INFO_HALF_DUPLEX; | |
2053 | ]]> | |
2054 | </programlisting> | |
2055 | </informalexample> | |
2056 | </para> | |
2057 | </section> | |
2058 | ||
2059 | <section id="pcm-interface-destructor"> | |
2060 | <title>... And the Destructor?</title> | |
2061 | <para> | |
2062 | The destructor for a pcm instance is not always | |
2063 | necessary. Since the pcm device will be released by the middle | |
3f03f7c5 | 2064 | layer code automatically, you don't have to call the destructor |
1da177e4 LT |
2065 | explicitly. |
2066 | </para> | |
2067 | ||
2068 | <para> | |
3f03f7c5 MO |
2069 | The destructor would be necessary if you created |
2070 | special records internally and needed to release them. In such a | |
1da177e4 LT |
2071 | case, set the destructor function to |
2072 | pcm->private_free: | |
2073 | ||
2074 | <example> | |
2075 | <title>PCM Instance with a Destructor</title> | |
2076 | <programlisting> | |
2077 | <![CDATA[ | |
446ab5f5 | 2078 | static void mychip_pcm_free(struct snd_pcm *pcm) |
1da177e4 | 2079 | { |
446ab5f5 | 2080 | struct mychip *chip = snd_pcm_chip(pcm); |
1da177e4 LT |
2081 | /* free your own data */ |
2082 | kfree(chip->my_private_pcm_data); | |
95a5b085 | 2083 | /* do what you like else */ |
1da177e4 LT |
2084 | .... |
2085 | } | |
2086 | ||
090015ae | 2087 | static int snd_mychip_new_pcm(struct mychip *chip) |
1da177e4 | 2088 | { |
446ab5f5 | 2089 | struct snd_pcm *pcm; |
1da177e4 LT |
2090 | .... |
2091 | /* allocate your own data */ | |
2092 | chip->my_private_pcm_data = kmalloc(...); | |
2093 | /* set the destructor */ | |
2094 | pcm->private_data = chip; | |
2095 | pcm->private_free = mychip_pcm_free; | |
2096 | .... | |
2097 | } | |
2098 | ]]> | |
2099 | </programlisting> | |
2100 | </example> | |
2101 | </para> | |
2102 | </section> | |
2103 | ||
2104 | <section id="pcm-interface-runtime"> | |
2105 | <title>Runtime Pointer - The Chest of PCM Information</title> | |
2106 | <para> | |
2107 | When the PCM substream is opened, a PCM runtime instance is | |
2108 | allocated and assigned to the substream. This pointer is | |
2109 | accessible via <constant>substream->runtime</constant>. | |
3f03f7c5 MO |
2110 | This runtime pointer holds most information you need |
2111 | to control the PCM: the copy of hw_params and sw_params configurations, the buffer | |
2112 | pointers, mmap records, spinlocks, etc. | |
1da177e4 LT |
2113 | </para> |
2114 | ||
2115 | <para> | |
2116 | The definition of runtime instance is found in | |
3f03f7c5 MO |
2117 | <filename><sound/pcm.h></filename>. Here are |
2118 | the contents of this file: | |
1da177e4 LT |
2119 | <informalexample> |
2120 | <programlisting> | |
2121 | <![CDATA[ | |
2122 | struct _snd_pcm_runtime { | |
2123 | /* -- Status -- */ | |
446ab5f5 | 2124 | struct snd_pcm_substream *trigger_master; |
1da177e4 LT |
2125 | snd_timestamp_t trigger_tstamp; /* trigger timestamp */ |
2126 | int overrange; | |
2127 | snd_pcm_uframes_t avail_max; | |
2128 | snd_pcm_uframes_t hw_ptr_base; /* Position at buffer restart */ | |
2129 | snd_pcm_uframes_t hw_ptr_interrupt; /* Position at interrupt time*/ | |
2130 | ||
2131 | /* -- HW params -- */ | |
2132 | snd_pcm_access_t access; /* access mode */ | |
2133 | snd_pcm_format_t format; /* SNDRV_PCM_FORMAT_* */ | |
2134 | snd_pcm_subformat_t subformat; /* subformat */ | |
2135 | unsigned int rate; /* rate in Hz */ | |
2136 | unsigned int channels; /* channels */ | |
2137 | snd_pcm_uframes_t period_size; /* period size */ | |
2138 | unsigned int periods; /* periods */ | |
2139 | snd_pcm_uframes_t buffer_size; /* buffer size */ | |
2140 | unsigned int tick_time; /* tick time */ | |
2141 | snd_pcm_uframes_t min_align; /* Min alignment for the format */ | |
2142 | size_t byte_align; | |
2143 | unsigned int frame_bits; | |
2144 | unsigned int sample_bits; | |
2145 | unsigned int info; | |
2146 | unsigned int rate_num; | |
2147 | unsigned int rate_den; | |
2148 | ||
2149 | /* -- SW params -- */ | |
07799e75 | 2150 | struct timespec tstamp_mode; /* mmap timestamp is updated */ |
1da177e4 LT |
2151 | unsigned int period_step; |
2152 | unsigned int sleep_min; /* min ticks to sleep */ | |
1da177e4 LT |
2153 | snd_pcm_uframes_t start_threshold; |
2154 | snd_pcm_uframes_t stop_threshold; | |
2155 | snd_pcm_uframes_t silence_threshold; /* Silence filling happens when | |
2156 | noise is nearest than this */ | |
2157 | snd_pcm_uframes_t silence_size; /* Silence filling size */ | |
2158 | snd_pcm_uframes_t boundary; /* pointers wrap point */ | |
2159 | ||
2160 | snd_pcm_uframes_t silenced_start; | |
2161 | snd_pcm_uframes_t silenced_size; | |
2162 | ||
2163 | snd_pcm_sync_id_t sync; /* hardware synchronization ID */ | |
2164 | ||
2165 | /* -- mmap -- */ | |
446ab5f5 TI |
2166 | volatile struct snd_pcm_mmap_status *status; |
2167 | volatile struct snd_pcm_mmap_control *control; | |
1da177e4 LT |
2168 | atomic_t mmap_count; |
2169 | ||
2170 | /* -- locking / scheduling -- */ | |
2171 | spinlock_t lock; | |
2172 | wait_queue_head_t sleep; | |
2173 | struct timer_list tick_timer; | |
2174 | struct fasync_struct *fasync; | |
2175 | ||
2176 | /* -- private section -- */ | |
2177 | void *private_data; | |
446ab5f5 | 2178 | void (*private_free)(struct snd_pcm_runtime *runtime); |
1da177e4 LT |
2179 | |
2180 | /* -- hardware description -- */ | |
446ab5f5 TI |
2181 | struct snd_pcm_hardware hw; |
2182 | struct snd_pcm_hw_constraints hw_constraints; | |
1da177e4 LT |
2183 | |
2184 | /* -- interrupt callbacks -- */ | |
446ab5f5 TI |
2185 | void (*transfer_ack_begin)(struct snd_pcm_substream *substream); |
2186 | void (*transfer_ack_end)(struct snd_pcm_substream *substream); | |
1da177e4 LT |
2187 | |
2188 | /* -- timer -- */ | |
2189 | unsigned int timer_resolution; /* timer resolution */ | |
2190 | ||
2191 | /* -- DMA -- */ | |
2192 | unsigned char *dma_area; /* DMA area */ | |
2193 | dma_addr_t dma_addr; /* physical bus address (not accessible from main CPU) */ | |
2194 | size_t dma_bytes; /* size of DMA area */ | |
2195 | ||
2196 | struct snd_dma_buffer *dma_buffer_p; /* allocated buffer */ | |
2197 | ||
2198 | #if defined(CONFIG_SND_PCM_OSS) || defined(CONFIG_SND_PCM_OSS_MODULE) | |
2199 | /* -- OSS things -- */ | |
446ab5f5 | 2200 | struct snd_pcm_oss_runtime oss; |
1da177e4 LT |
2201 | #endif |
2202 | }; | |
2203 | ]]> | |
2204 | </programlisting> | |
2205 | </informalexample> | |
2206 | </para> | |
2207 | ||
2208 | <para> | |
2209 | For the operators (callbacks) of each sound driver, most of | |
2210 | these records are supposed to be read-only. Only the PCM | |
3f03f7c5 | 2211 | middle-layer changes / updates them. The exceptions are |
1da177e4 LT |
2212 | the hardware description (hw), interrupt callbacks |
2213 | (transfer_ack_xxx), DMA buffer information, and the private | |
2214 | data. Besides, if you use the standard buffer allocation | |
2215 | method via <function>snd_pcm_lib_malloc_pages()</function>, | |
2216 | you don't need to set the DMA buffer information by yourself. | |
2217 | </para> | |
2218 | ||
2219 | <para> | |
2220 | In the sections below, important records are explained. | |
2221 | </para> | |
2222 | ||
2223 | <section id="pcm-interface-runtime-hw"> | |
2224 | <title>Hardware Description</title> | |
2225 | <para> | |
446ab5f5 | 2226 | The hardware descriptor (struct <structname>snd_pcm_hardware</structname>) |
1da177e4 LT |
2227 | contains the definitions of the fundamental hardware |
2228 | configuration. Above all, you'll need to define this in | |
2229 | <link linkend="pcm-interface-operators-open-callback"><citetitle> | |
2230 | the open callback</citetitle></link>. | |
2231 | Note that the runtime instance holds the copy of the | |
2232 | descriptor, not the pointer to the existing descriptor. That | |
2233 | is, in the open callback, you can modify the copied descriptor | |
2234 | (<constant>runtime->hw</constant>) as you need. For example, if the maximum | |
2235 | number of channels is 1 only on some chip models, you can | |
2236 | still use the same hardware descriptor and change the | |
2237 | channels_max later: | |
2238 | <informalexample> | |
2239 | <programlisting> | |
2240 | <![CDATA[ | |
446ab5f5 | 2241 | struct snd_pcm_runtime *runtime = substream->runtime; |
1da177e4 LT |
2242 | ... |
2243 | runtime->hw = snd_mychip_playback_hw; /* common definition */ | |
2244 | if (chip->model == VERY_OLD_ONE) | |
2245 | runtime->hw.channels_max = 1; | |
2246 | ]]> | |
2247 | </programlisting> | |
2248 | </informalexample> | |
2249 | </para> | |
2250 | ||
2251 | <para> | |
3f03f7c5 | 2252 | Typically, you'll have a hardware descriptor as below: |
1da177e4 LT |
2253 | <informalexample> |
2254 | <programlisting> | |
2255 | <![CDATA[ | |
446ab5f5 | 2256 | static struct snd_pcm_hardware snd_mychip_playback_hw = { |
1da177e4 LT |
2257 | .info = (SNDRV_PCM_INFO_MMAP | |
2258 | SNDRV_PCM_INFO_INTERLEAVED | | |
2259 | SNDRV_PCM_INFO_BLOCK_TRANSFER | | |
2260 | SNDRV_PCM_INFO_MMAP_VALID), | |
2261 | .formats = SNDRV_PCM_FMTBIT_S16_LE, | |
2262 | .rates = SNDRV_PCM_RATE_8000_48000, | |
2263 | .rate_min = 8000, | |
2264 | .rate_max = 48000, | |
2265 | .channels_min = 2, | |
2266 | .channels_max = 2, | |
2267 | .buffer_bytes_max = 32768, | |
2268 | .period_bytes_min = 4096, | |
2269 | .period_bytes_max = 32768, | |
2270 | .periods_min = 1, | |
2271 | .periods_max = 1024, | |
2272 | }; | |
2273 | ]]> | |
2274 | </programlisting> | |
2275 | </informalexample> | |
2276 | </para> | |
2277 | ||
2278 | <para> | |
2279 | <itemizedlist> | |
2280 | <listitem><para> | |
2281 | The <structfield>info</structfield> field contains the type and | |
2282 | capabilities of this pcm. The bit flags are defined in | |
2283 | <filename><sound/asound.h></filename> as | |
2284 | <constant>SNDRV_PCM_INFO_XXX</constant>. Here, at least, you | |
2285 | have to specify whether the mmap is supported and which | |
2286 | interleaved format is supported. | |
04044b81 | 2287 | When the hardware supports mmap, add the |
1da177e4 LT |
2288 | <constant>SNDRV_PCM_INFO_MMAP</constant> flag here. When the |
2289 | hardware supports the interleaved or the non-interleaved | |
3f03f7c5 | 2290 | formats, <constant>SNDRV_PCM_INFO_INTERLEAVED</constant> or |
1da177e4 LT |
2291 | <constant>SNDRV_PCM_INFO_NONINTERLEAVED</constant> flag must |
2292 | be set, respectively. If both are supported, you can set both, | |
2293 | too. | |
2294 | </para> | |
2295 | ||
2296 | <para> | |
2297 | In the above example, <constant>MMAP_VALID</constant> and | |
3f03f7c5 | 2298 | <constant>BLOCK_TRANSFER</constant> are specified for the OSS mmap |
1da177e4 LT |
2299 | mode. Usually both are set. Of course, |
2300 | <constant>MMAP_VALID</constant> is set only if the mmap is | |
2301 | really supported. | |
2302 | </para> | |
2303 | ||
2304 | <para> | |
2305 | The other possible flags are | |
2306 | <constant>SNDRV_PCM_INFO_PAUSE</constant> and | |
2307 | <constant>SNDRV_PCM_INFO_RESUME</constant>. The | |
2308 | <constant>PAUSE</constant> bit means that the pcm supports the | |
2309 | <quote>pause</quote> operation, while the | |
2310 | <constant>RESUME</constant> bit means that the pcm supports | |
5fe76e4d | 2311 | the full <quote>suspend/resume</quote> operation. |
3f03f7c5 | 2312 | If the <constant>PAUSE</constant> flag is set, |
5fe76e4d TI |
2313 | the <structfield>trigger</structfield> callback below |
2314 | must handle the corresponding (pause push/release) commands. | |
2315 | The suspend/resume trigger commands can be defined even without | |
3f03f7c5 | 2316 | the <constant>RESUME</constant> flag. See <link |
5fe76e4d TI |
2317 | linkend="power-management"><citetitle> |
2318 | Power Management</citetitle></link> section for details. | |
1da177e4 LT |
2319 | </para> |
2320 | ||
2321 | <para> | |
2322 | When the PCM substreams can be synchronized (typically, | |
5bda9fa1 | 2323 | synchronized start/stop of a playback and a capture streams), |
1da177e4 LT |
2324 | you can give <constant>SNDRV_PCM_INFO_SYNC_START</constant>, |
2325 | too. In this case, you'll need to check the linked-list of | |
2326 | PCM substreams in the trigger callback. This will be | |
2327 | described in the later section. | |
2328 | </para> | |
2329 | </listitem> | |
2330 | ||
2331 | <listitem> | |
2332 | <para> | |
2333 | <structfield>formats</structfield> field contains the bit-flags | |
2334 | of supported formats (<constant>SNDRV_PCM_FMTBIT_XXX</constant>). | |
2335 | If the hardware supports more than one format, give all or'ed | |
2336 | bits. In the example above, the signed 16bit little-endian | |
2337 | format is specified. | |
2338 | </para> | |
2339 | </listitem> | |
2340 | ||
2341 | <listitem> | |
2342 | <para> | |
2343 | <structfield>rates</structfield> field contains the bit-flags of | |
2344 | supported rates (<constant>SNDRV_PCM_RATE_XXX</constant>). | |
2345 | When the chip supports continuous rates, pass | |
2346 | <constant>CONTINUOUS</constant> bit additionally. | |
2347 | The pre-defined rate bits are provided only for typical | |
2348 | rates. If your chip supports unconventional rates, you need to add | |
3f03f7c5 | 2349 | the <constant>KNOT</constant> bit and set up the hardware |
1da177e4 LT |
2350 | constraint manually (explained later). |
2351 | </para> | |
2352 | </listitem> | |
2353 | ||
2354 | <listitem> | |
2355 | <para> | |
2356 | <structfield>rate_min</structfield> and | |
3f03f7c5 MO |
2357 | <structfield>rate_max</structfield> define the minimum and |
2358 | maximum sample rate. This should correspond somehow to | |
1da177e4 LT |
2359 | <structfield>rates</structfield> bits. |
2360 | </para> | |
2361 | </listitem> | |
2362 | ||
2363 | <listitem> | |
2364 | <para> | |
2365 | <structfield>channel_min</structfield> and | |
2366 | <structfield>channel_max</structfield> | |
3f03f7c5 | 2367 | define, as you might already expected, the minimum and maximum |
1da177e4 LT |
2368 | number of channels. |
2369 | </para> | |
2370 | </listitem> | |
2371 | ||
2372 | <listitem> | |
2373 | <para> | |
2374 | <structfield>buffer_bytes_max</structfield> defines the | |
3f03f7c5 | 2375 | maximum buffer size in bytes. There is no |
1da177e4 | 2376 | <structfield>buffer_bytes_min</structfield> field, since |
3f03f7c5 MO |
2377 | it can be calculated from the minimum period size and the |
2378 | minimum number of periods. | |
1da177e4 | 2379 | Meanwhile, <structfield>period_bytes_min</structfield> and |
3f03f7c5 | 2380 | define the minimum and maximum size of the period in bytes. |
1da177e4 | 2381 | <structfield>periods_max</structfield> and |
3f03f7c5 MO |
2382 | <structfield>periods_min</structfield> define the maximum and |
2383 | minimum number of periods in the buffer. | |
1da177e4 LT |
2384 | </para> |
2385 | ||
2386 | <para> | |
3f03f7c5 MO |
2387 | The <quote>period</quote> is a term that corresponds to |
2388 | a fragment in the OSS world. The period defines the size at | |
2389 | which a PCM interrupt is generated. This size strongly | |
1da177e4 LT |
2390 | depends on the hardware. |
2391 | Generally, the smaller period size will give you more | |
2392 | interrupts, that is, more controls. | |
2393 | In the case of capture, this size defines the input latency. | |
2394 | On the other hand, the whole buffer size defines the | |
2395 | output latency for the playback direction. | |
2396 | </para> | |
2397 | </listitem> | |
2398 | ||
2399 | <listitem> | |
2400 | <para> | |
2401 | There is also a field <structfield>fifo_size</structfield>. | |
3f03f7c5 MO |
2402 | This specifies the size of the hardware FIFO, but currently it |
2403 | is neither used in the driver nor in the alsa-lib. So, you | |
1da177e4 LT |
2404 | can ignore this field. |
2405 | </para> | |
2406 | </listitem> | |
2407 | </itemizedlist> | |
2408 | </para> | |
2409 | </section> | |
2410 | ||
2411 | <section id="pcm-interface-runtime-config"> | |
2412 | <title>PCM Configurations</title> | |
2413 | <para> | |
2414 | Ok, let's go back again to the PCM runtime records. | |
2415 | The most frequently referred records in the runtime instance are | |
2416 | the PCM configurations. | |
3f03f7c5 | 2417 | The PCM configurations are stored in the runtime instance |
1da177e4 LT |
2418 | after the application sends <type>hw_params</type> data via |
2419 | alsa-lib. There are many fields copied from hw_params and | |
2420 | sw_params structs. For example, | |
2421 | <structfield>format</structfield> holds the format type | |
2422 | chosen by the application. This field contains the enum value | |
2423 | <constant>SNDRV_PCM_FORMAT_XXX</constant>. | |
2424 | </para> | |
2425 | ||
2426 | <para> | |
2427 | One thing to be noted is that the configured buffer and period | |
3f03f7c5 | 2428 | sizes are stored in <quote>frames</quote> in the runtime. |
1da177e4 LT |
2429 | In the ALSA world, 1 frame = channels * samples-size. |
2430 | For conversion between frames and bytes, you can use the | |
3f03f7c5 MO |
2431 | <function>frames_to_bytes()</function> and |
2432 | <function>bytes_to_frames()</function> helper functions. | |
1da177e4 LT |
2433 | <informalexample> |
2434 | <programlisting> | |
2435 | <![CDATA[ | |
2436 | period_bytes = frames_to_bytes(runtime, runtime->period_size); | |
2437 | ]]> | |
2438 | </programlisting> | |
2439 | </informalexample> | |
2440 | </para> | |
2441 | ||
2442 | <para> | |
2443 | Also, many software parameters (sw_params) are | |
2444 | stored in frames, too. Please check the type of the field. | |
2445 | <type>snd_pcm_uframes_t</type> is for the frames as unsigned | |
2446 | integer while <type>snd_pcm_sframes_t</type> is for the frames | |
2447 | as signed integer. | |
2448 | </para> | |
2449 | </section> | |
2450 | ||
2451 | <section id="pcm-interface-runtime-dma"> | |
2452 | <title>DMA Buffer Information</title> | |
2453 | <para> | |
2454 | The DMA buffer is defined by the following four fields, | |
2455 | <structfield>dma_area</structfield>, | |
2456 | <structfield>dma_addr</structfield>, | |
2457 | <structfield>dma_bytes</structfield> and | |
2458 | <structfield>dma_private</structfield>. | |
2459 | The <structfield>dma_area</structfield> holds the buffer | |
2460 | pointer (the logical address). You can call | |
2461 | <function>memcpy</function> from/to | |
2462 | this pointer. Meanwhile, <structfield>dma_addr</structfield> | |
2463 | holds the physical address of the buffer. This field is | |
2464 | specified only when the buffer is a linear buffer. | |
2465 | <structfield>dma_bytes</structfield> holds the size of buffer | |
2466 | in bytes. <structfield>dma_private</structfield> is used for | |
2467 | the ALSA DMA allocator. | |
2468 | </para> | |
2469 | ||
2470 | <para> | |
2471 | If you use a standard ALSA function, | |
2472 | <function>snd_pcm_lib_malloc_pages()</function>, for | |
2473 | allocating the buffer, these fields are set by the ALSA middle | |
2474 | layer, and you should <emphasis>not</emphasis> change them by | |
2475 | yourself. You can read them but not write them. | |
2476 | On the other hand, if you want to allocate the buffer by | |
2477 | yourself, you'll need to manage it in hw_params callback. | |
2478 | At least, <structfield>dma_bytes</structfield> is mandatory. | |
2479 | <structfield>dma_area</structfield> is necessary when the | |
2480 | buffer is mmapped. If your driver doesn't support mmap, this | |
2481 | field is not necessary. <structfield>dma_addr</structfield> | |
3f03f7c5 | 2482 | is also optional. You can use |
1da177e4 LT |
2483 | <structfield>dma_private</structfield> as you like, too. |
2484 | </para> | |
2485 | </section> | |
2486 | ||
2487 | <section id="pcm-interface-runtime-status"> | |
2488 | <title>Running Status</title> | |
2489 | <para> | |
2490 | The running status can be referred via <constant>runtime->status</constant>. | |
3f03f7c5 | 2491 | This is the pointer to the struct <structname>snd_pcm_mmap_status</structname> |
1da177e4 LT |
2492 | record. For example, you can get the current DMA hardware |
2493 | pointer via <constant>runtime->status->hw_ptr</constant>. | |
2494 | </para> | |
2495 | ||
2496 | <para> | |
2497 | The DMA application pointer can be referred via | |
3f03f7c5 | 2498 | <constant>runtime->control</constant>, which points to the |
446ab5f5 | 2499 | struct <structname>snd_pcm_mmap_control</structname> record. |
1da177e4 LT |
2500 | However, accessing directly to this value is not recommended. |
2501 | </para> | |
2502 | </section> | |
2503 | ||
2504 | <section id="pcm-interface-runtime-private"> | |
2505 | <title>Private Data</title> | |
2506 | <para> | |
2507 | You can allocate a record for the substream and store it in | |
2508 | <constant>runtime->private_data</constant>. Usually, this | |
3f03f7c5 | 2509 | is done in |
1da177e4 LT |
2510 | <link linkend="pcm-interface-operators-open-callback"><citetitle> |
2511 | the open callback</citetitle></link>. | |
2512 | Don't mix this with <constant>pcm->private_data</constant>. | |
3f03f7c5 | 2513 | The <constant>pcm->private_data</constant> usually points to the |
1da177e4 | 2514 | chip instance assigned statically at the creation of PCM, while the |
3f03f7c5 MO |
2515 | <constant>runtime->private_data</constant> points to a dynamic |
2516 | data structure created at the PCM open callback. | |
1da177e4 LT |
2517 | |
2518 | <informalexample> | |
2519 | <programlisting> | |
2520 | <![CDATA[ | |
446ab5f5 | 2521 | static int snd_xxx_open(struct snd_pcm_substream *substream) |
1da177e4 | 2522 | { |
446ab5f5 | 2523 | struct my_pcm_data *data; |
1da177e4 LT |
2524 | .... |
2525 | data = kmalloc(sizeof(*data), GFP_KERNEL); | |
2526 | substream->runtime->private_data = data; | |
2527 | .... | |
2528 | } | |
2529 | ]]> | |
2530 | </programlisting> | |
2531 | </informalexample> | |
2532 | </para> | |
2533 | ||
2534 | <para> | |
2535 | The allocated object must be released in | |
2536 | <link linkend="pcm-interface-operators-open-callback"><citetitle> | |
2537 | the close callback</citetitle></link>. | |
2538 | </para> | |
2539 | </section> | |
2540 | ||
2541 | <section id="pcm-interface-runtime-intr"> | |
2542 | <title>Interrupt Callbacks</title> | |
2543 | <para> | |
2544 | The field <structfield>transfer_ack_begin</structfield> and | |
2545 | <structfield>transfer_ack_end</structfield> are called at | |
3f03f7c5 | 2546 | the beginning and at the end of |
1da177e4 LT |
2547 | <function>snd_pcm_period_elapsed()</function>, respectively. |
2548 | </para> | |
2549 | </section> | |
2550 | ||
2551 | </section> | |
2552 | ||
2553 | <section id="pcm-interface-operators"> | |
2554 | <title>Operators</title> | |
2555 | <para> | |
3f03f7c5 | 2556 | OK, now let me give details about each pcm callback |
1da177e4 | 2557 | (<parameter>ops</parameter>). In general, every callback must |
3f03f7c5 MO |
2558 | return 0 if successful, or a negative error number |
2559 | such as <constant>-EINVAL</constant>. To choose an appropriate | |
2560 | error number, it is advised to check what value other parts of | |
2561 | the kernel return when the same kind of request fails. | |
1da177e4 LT |
2562 | </para> |
2563 | ||
2564 | <para> | |
2565 | The callback function takes at least the argument with | |
3f03f7c5 MO |
2566 | <structname>snd_pcm_substream</structname> pointer. To retrieve |
2567 | the chip record from the given substream instance, you can use the | |
1da177e4 LT |
2568 | following macro. |
2569 | ||
2570 | <informalexample> | |
2571 | <programlisting> | |
2572 | <![CDATA[ | |
2573 | int xxx() { | |
446ab5f5 | 2574 | struct mychip *chip = snd_pcm_substream_chip(substream); |
1da177e4 LT |
2575 | .... |
2576 | } | |
2577 | ]]> | |
2578 | </programlisting> | |
2579 | </informalexample> | |
2580 | ||
2581 | The macro reads <constant>substream->private_data</constant>, | |
2582 | which is a copy of <constant>pcm->private_data</constant>. | |
2583 | You can override the former if you need to assign different data | |
3f03f7c5 | 2584 | records per PCM substream. For example, the cmi8330 driver assigns |
1da177e4 LT |
2585 | different private_data for playback and capture directions, |
2586 | because it uses two different codecs (SB- and AD-compatible) for | |
2587 | different directions. | |
2588 | </para> | |
2589 | ||
2590 | <section id="pcm-interface-operators-open-callback"> | |
2591 | <title>open callback</title> | |
2592 | <para> | |
2593 | <informalexample> | |
2594 | <programlisting> | |
2595 | <![CDATA[ | |
446ab5f5 | 2596 | static int snd_xxx_open(struct snd_pcm_substream *substream); |
1da177e4 LT |
2597 | ]]> |
2598 | </programlisting> | |
2599 | </informalexample> | |
2600 | ||
2601 | This is called when a pcm substream is opened. | |
2602 | </para> | |
2603 | ||
2604 | <para> | |
2605 | At least, here you have to initialize the runtime->hw | |
2606 | record. Typically, this is done by like this: | |
2607 | ||
2608 | <informalexample> | |
2609 | <programlisting> | |
2610 | <![CDATA[ | |
446ab5f5 | 2611 | static int snd_xxx_open(struct snd_pcm_substream *substream) |
1da177e4 | 2612 | { |
446ab5f5 TI |
2613 | struct mychip *chip = snd_pcm_substream_chip(substream); |
2614 | struct snd_pcm_runtime *runtime = substream->runtime; | |
1da177e4 LT |
2615 | |
2616 | runtime->hw = snd_mychip_playback_hw; | |
2617 | return 0; | |
2618 | } | |
2619 | ]]> | |
2620 | </programlisting> | |
2621 | </informalexample> | |
2622 | ||
2623 | where <parameter>snd_mychip_playback_hw</parameter> is the | |
2624 | pre-defined hardware description. | |
2625 | </para> | |
2626 | ||
2627 | <para> | |
2628 | You can allocate a private data in this callback, as described | |
2629 | in <link linkend="pcm-interface-runtime-private"><citetitle> | |
2630 | Private Data</citetitle></link> section. | |
2631 | </para> | |
2632 | ||
2633 | <para> | |
2634 | If the hardware configuration needs more constraints, set the | |
2635 | hardware constraints here, too. | |
2636 | See <link linkend="pcm-interface-constraints"><citetitle> | |
2637 | Constraints</citetitle></link> for more details. | |
2638 | </para> | |
2639 | </section> | |
2640 | ||
2641 | <section id="pcm-interface-operators-close-callback"> | |
2642 | <title>close callback</title> | |
2643 | <para> | |
2644 | <informalexample> | |
2645 | <programlisting> | |
2646 | <![CDATA[ | |
446ab5f5 | 2647 | static int snd_xxx_close(struct snd_pcm_substream *substream); |
1da177e4 LT |
2648 | ]]> |
2649 | </programlisting> | |
2650 | </informalexample> | |
2651 | ||
2652 | Obviously, this is called when a pcm substream is closed. | |
2653 | </para> | |
2654 | ||
2655 | <para> | |
2656 | Any private instance for a pcm substream allocated in the | |
2657 | open callback will be released here. | |
2658 | ||
2659 | <informalexample> | |
2660 | <programlisting> | |
2661 | <![CDATA[ | |
446ab5f5 | 2662 | static int snd_xxx_close(struct snd_pcm_substream *substream) |
1da177e4 LT |
2663 | { |
2664 | .... | |
2665 | kfree(substream->runtime->private_data); | |
2666 | .... | |
2667 | } | |
2668 | ]]> | |
2669 | </programlisting> | |
2670 | </informalexample> | |
2671 | </para> | |
2672 | </section> | |
2673 | ||
2674 | <section id="pcm-interface-operators-ioctl-callback"> | |
2675 | <title>ioctl callback</title> | |
2676 | <para> | |
3f03f7c5 | 2677 | This is used for any special call to pcm ioctls. But |
1da177e4 LT |
2678 | usually you can pass a generic ioctl callback, |
2679 | <function>snd_pcm_lib_ioctl</function>. | |
2680 | </para> | |
2681 | </section> | |
2682 | ||
2683 | <section id="pcm-interface-operators-hw-params-callback"> | |
2684 | <title>hw_params callback</title> | |
2685 | <para> | |
2686 | <informalexample> | |
2687 | <programlisting> | |
2688 | <![CDATA[ | |
446ab5f5 TI |
2689 | static int snd_xxx_hw_params(struct snd_pcm_substream *substream, |
2690 | struct snd_pcm_hw_params *hw_params); | |
1da177e4 LT |
2691 | ]]> |
2692 | </programlisting> | |
2693 | </informalexample> | |
1da177e4 LT |
2694 | </para> |
2695 | ||
2696 | <para> | |
2697 | This is called when the hardware parameter | |
2698 | (<structfield>hw_params</structfield>) is set | |
2699 | up by the application, | |
2700 | that is, once when the buffer size, the period size, the | |
2701 | format, etc. are defined for the pcm substream. | |
2702 | </para> | |
2703 | ||
2704 | <para> | |
3f03f7c5 | 2705 | Many hardware setups should be done in this callback, |
1da177e4 LT |
2706 | including the allocation of buffers. |
2707 | </para> | |
2708 | ||
2709 | <para> | |
2710 | Parameters to be initialized are retrieved by | |
3f03f7c5 | 2711 | <function>params_xxx()</function> macros. To allocate |
1da177e4 LT |
2712 | buffer, you can call a helper function, |
2713 | ||
2714 | <informalexample> | |
2715 | <programlisting> | |
2716 | <![CDATA[ | |
2717 | snd_pcm_lib_malloc_pages(substream, params_buffer_bytes(hw_params)); | |
2718 | ]]> | |
2719 | </programlisting> | |
2720 | </informalexample> | |
2721 | ||
2722 | <function>snd_pcm_lib_malloc_pages()</function> is available | |
2723 | only when the DMA buffers have been pre-allocated. | |
2724 | See the section <link | |
2725 | linkend="buffer-and-memory-buffer-types"><citetitle> | |
2726 | Buffer Types</citetitle></link> for more details. | |
2727 | </para> | |
2728 | ||
2729 | <para> | |
2730 | Note that this and <structfield>prepare</structfield> callbacks | |
2731 | may be called multiple times per initialization. | |
2732 | For example, the OSS emulation may | |
2733 | call these callbacks at each change via its ioctl. | |
2734 | </para> | |
2735 | ||
2736 | <para> | |
3f03f7c5 MO |
2737 | Thus, you need to be careful not to allocate the same buffers |
2738 | many times, which will lead to memory leaks! Calling the | |
1da177e4 LT |
2739 | helper function above many times is OK. It will release the |
2740 | previous buffer automatically when it was already allocated. | |
2741 | </para> | |
2742 | ||
2743 | <para> | |
2744 | Another note is that this callback is non-atomic | |
941a74ca TI |
2745 | (schedulable) as default, i.e. when no |
2746 | <structfield>nonatomic</structfield> flag set. | |
2747 | This is important, because the | |
1da177e4 | 2748 | <structfield>trigger</structfield> callback |
3f03f7c5 | 2749 | is atomic (non-schedulable). That is, mutexes or any |
1da177e4 LT |
2750 | schedule-related functions are not available in |
2751 | <structfield>trigger</structfield> callback. | |
2752 | Please see the subsection | |
2753 | <link linkend="pcm-interface-atomicity"><citetitle> | |
2754 | Atomicity</citetitle></link> for details. | |
2755 | </para> | |
2756 | </section> | |
2757 | ||
2758 | <section id="pcm-interface-operators-hw-free-callback"> | |
2759 | <title>hw_free callback</title> | |
2760 | <para> | |
2761 | <informalexample> | |
2762 | <programlisting> | |
2763 | <![CDATA[ | |
446ab5f5 | 2764 | static int snd_xxx_hw_free(struct snd_pcm_substream *substream); |
1da177e4 LT |
2765 | ]]> |
2766 | </programlisting> | |
2767 | </informalexample> | |
2768 | </para> | |
2769 | ||
2770 | <para> | |
2771 | This is called to release the resources allocated via | |
2772 | <structfield>hw_params</structfield>. For example, releasing the | |
2773 | buffer via | |
2774 | <function>snd_pcm_lib_malloc_pages()</function> is done by | |
2775 | calling the following: | |
2776 | ||
2777 | <informalexample> | |
2778 | <programlisting> | |
2779 | <![CDATA[ | |
2780 | snd_pcm_lib_free_pages(substream); | |
2781 | ]]> | |
2782 | </programlisting> | |
2783 | </informalexample> | |
2784 | </para> | |
2785 | ||
2786 | <para> | |
2787 | This function is always called before the close callback is called. | |
2788 | Also, the callback may be called multiple times, too. | |
2789 | Keep track whether the resource was already released. | |
2790 | </para> | |
2791 | </section> | |
2792 | ||
2793 | <section id="pcm-interface-operators-prepare-callback"> | |
2794 | <title>prepare callback</title> | |
2795 | <para> | |
2796 | <informalexample> | |
2797 | <programlisting> | |
2798 | <![CDATA[ | |
446ab5f5 | 2799 | static int snd_xxx_prepare(struct snd_pcm_substream *substream); |
1da177e4 LT |
2800 | ]]> |
2801 | </programlisting> | |
2802 | </informalexample> | |
2803 | </para> | |
2804 | ||
2805 | <para> | |
2806 | This callback is called when the pcm is | |
2807 | <quote>prepared</quote>. You can set the format type, sample | |
2808 | rate, etc. here. The difference from | |
2809 | <structfield>hw_params</structfield> is that the | |
3f03f7c5 | 2810 | <structfield>prepare</structfield> callback will be called each |
1da177e4 LT |
2811 | time |
2812 | <function>snd_pcm_prepare()</function> is called, i.e. when | |
3f03f7c5 | 2813 | recovering after underruns, etc. |
1da177e4 LT |
2814 | </para> |
2815 | ||
2816 | <para> | |
3f03f7c5 MO |
2817 | Note that this callback is now non-atomic. |
2818 | You can use schedule-related functions safely in this callback. | |
1da177e4 LT |
2819 | </para> |
2820 | ||
2821 | <para> | |
2822 | In this and the following callbacks, you can refer to the | |
2823 | values via the runtime record, | |
2824 | substream->runtime. | |
2825 | For example, to get the current | |
2826 | rate, format or channels, access to | |
2827 | runtime->rate, | |
2828 | runtime->format or | |
2829 | runtime->channels, respectively. | |
2830 | The physical address of the allocated buffer is set to | |
2831 | runtime->dma_area. The buffer and period sizes are | |
2832 | in runtime->buffer_size and runtime->period_size, | |
2833 | respectively. | |
2834 | </para> | |
2835 | ||
2836 | <para> | |
2837 | Be careful that this callback will be called many times at | |
3f03f7c5 | 2838 | each setup, too. |
1da177e4 LT |
2839 | </para> |
2840 | </section> | |
2841 | ||
2842 | <section id="pcm-interface-operators-trigger-callback"> | |
2843 | <title>trigger callback</title> | |
2844 | <para> | |
2845 | <informalexample> | |
2846 | <programlisting> | |
2847 | <![CDATA[ | |
446ab5f5 | 2848 | static int snd_xxx_trigger(struct snd_pcm_substream *substream, int cmd); |
1da177e4 LT |
2849 | ]]> |
2850 | </programlisting> | |
2851 | </informalexample> | |
2852 | ||
2853 | This is called when the pcm is started, stopped or paused. | |
2854 | </para> | |
2855 | ||
2856 | <para> | |
2857 | Which action is specified in the second argument, | |
2858 | <constant>SNDRV_PCM_TRIGGER_XXX</constant> in | |
2859 | <filename><sound/pcm.h></filename>. At least, | |
3f03f7c5 | 2860 | the <constant>START</constant> and <constant>STOP</constant> |
1da177e4 LT |
2861 | commands must be defined in this callback. |
2862 | ||
2863 | <informalexample> | |
2864 | <programlisting> | |
2865 | <![CDATA[ | |
2866 | switch (cmd) { | |
2867 | case SNDRV_PCM_TRIGGER_START: | |
95a5b085 | 2868 | /* do something to start the PCM engine */ |
1da177e4 LT |
2869 | break; |
2870 | case SNDRV_PCM_TRIGGER_STOP: | |
95a5b085 | 2871 | /* do something to stop the PCM engine */ |
1da177e4 LT |
2872 | break; |
2873 | default: | |
2874 | return -EINVAL; | |
2875 | } | |
2876 | ]]> | |
2877 | </programlisting> | |
2878 | </informalexample> | |
2879 | </para> | |
2880 | ||
2881 | <para> | |
3f03f7c5 | 2882 | When the pcm supports the pause operation (given in the info |
d4dab5ab | 2883 | field of the hardware table), the <constant>PAUSE_PUSH</constant> |
1da177e4 LT |
2884 | and <constant>PAUSE_RELEASE</constant> commands must be |
2885 | handled here, too. The former is the command to pause the pcm, | |
2886 | and the latter to restart the pcm again. | |
2887 | </para> | |
2888 | ||
2889 | <para> | |
5fe76e4d TI |
2890 | When the pcm supports the suspend/resume operation, |
2891 | regardless of full or partial suspend/resume support, | |
3f03f7c5 | 2892 | the <constant>SUSPEND</constant> and <constant>RESUME</constant> |
1da177e4 LT |
2893 | commands must be handled, too. |
2894 | These commands are issued when the power-management status is | |
2895 | changed. Obviously, the <constant>SUSPEND</constant> and | |
3f03f7c5 MO |
2896 | <constant>RESUME</constant> commands |
2897 | suspend and resume the pcm substream, and usually, they | |
2898 | are identical to the <constant>STOP</constant> and | |
1da177e4 | 2899 | <constant>START</constant> commands, respectively. |
3f03f7c5 | 2900 | See the <link linkend="power-management"><citetitle> |
5fe76e4d | 2901 | Power Management</citetitle></link> section for details. |
1da177e4 LT |
2902 | </para> |
2903 | ||
2904 | <para> | |
941a74ca TI |
2905 | As mentioned, this callback is atomic as default unless |
2906 | <structfield>nonatomic</structfield> flag set, and | |
2907 | you cannot call functions which may sleep. | |
1da177e4 LT |
2908 | The trigger callback should be as minimal as possible, |
2909 | just really triggering the DMA. The other stuff should be | |
2910 | initialized hw_params and prepare callbacks properly | |
2911 | beforehand. | |
2912 | </para> | |
2913 | </section> | |
2914 | ||
2915 | <section id="pcm-interface-operators-pointer-callback"> | |
2916 | <title>pointer callback</title> | |
2917 | <para> | |
2918 | <informalexample> | |
2919 | <programlisting> | |
2920 | <![CDATA[ | |
446ab5f5 | 2921 | static snd_pcm_uframes_t snd_xxx_pointer(struct snd_pcm_substream *substream) |
1da177e4 LT |
2922 | ]]> |
2923 | </programlisting> | |
2924 | </informalexample> | |
2925 | ||
2926 | This callback is called when the PCM middle layer inquires | |
2927 | the current hardware position on the buffer. The position must | |
3f03f7c5 MO |
2928 | be returned in frames, |
2929 | ranging from 0 to buffer_size - 1. | |
1da177e4 LT |
2930 | </para> |
2931 | ||
2932 | <para> | |
2933 | This is called usually from the buffer-update routine in the | |
2934 | pcm middle layer, which is invoked when | |
2935 | <function>snd_pcm_period_elapsed()</function> is called in the | |
2936 | interrupt routine. Then the pcm middle layer updates the | |
2937 | position and calculates the available space, and wakes up the | |
2938 | sleeping poll threads, etc. | |
2939 | </para> | |
2940 | ||
2941 | <para> | |
941a74ca | 2942 | This callback is also atomic as default. |
1da177e4 LT |
2943 | </para> |
2944 | </section> | |
2945 | ||
2946 | <section id="pcm-interface-operators-copy-silence"> | |
2947 | <title>copy and silence callbacks</title> | |
2948 | <para> | |
2949 | These callbacks are not mandatory, and can be omitted in | |
2950 | most cases. These callbacks are used when the hardware buffer | |
3f03f7c5 | 2951 | cannot be in the normal memory space. Some chips have their |
1da177e4 LT |
2952 | own buffer on the hardware which is not mappable. In such a |
2953 | case, you have to transfer the data manually from the memory | |
2954 | buffer to the hardware buffer. Or, if the buffer is | |
2955 | non-contiguous on both physical and virtual memory spaces, | |
2956 | these callbacks must be defined, too. | |
2957 | </para> | |
2958 | ||
2959 | <para> | |
2960 | If these two callbacks are defined, copy and set-silence | |
2961 | operations are done by them. The detailed will be described in | |
2962 | the later section <link | |
2963 | linkend="buffer-and-memory"><citetitle>Buffer and Memory | |
2964 | Management</citetitle></link>. | |
2965 | </para> | |
2966 | </section> | |
2967 | ||
2968 | <section id="pcm-interface-operators-ack"> | |
2969 | <title>ack callback</title> | |
2970 | <para> | |
2971 | This callback is also not mandatory. This callback is called | |
2972 | when the appl_ptr is updated in read or write operations. | |
2973 | Some drivers like emu10k1-fx and cs46xx need to track the | |
2974 | current appl_ptr for the internal buffer, and this callback | |
2975 | is useful only for such a purpose. | |
2976 | </para> | |
2977 | <para> | |
941a74ca | 2978 | This callback is atomic as default. |
1da177e4 LT |
2979 | </para> |
2980 | </section> | |
2981 | ||
2982 | <section id="pcm-interface-operators-page-callback"> | |
2983 | <title>page callback</title> | |
2984 | ||
2985 | <para> | |
3f03f7c5 MO |
2986 | This callback is optional too. This callback is used |
2987 | mainly for non-contiguous buffers. The mmap calls this | |
1da177e4 LT |
2988 | callback to get the page address. Some examples will be |
2989 | explained in the later section <link | |
2990 | linkend="buffer-and-memory"><citetitle>Buffer and Memory | |
2991 | Management</citetitle></link>, too. | |
2992 | </para> | |
2993 | </section> | |
2994 | </section> | |
2995 | ||
2996 | <section id="pcm-interface-interrupt-handler"> | |
2997 | <title>Interrupt Handler</title> | |
2998 | <para> | |
2999 | The rest of pcm stuff is the PCM interrupt handler. The | |
3000 | role of PCM interrupt handler in the sound driver is to update | |
3001 | the buffer position and to tell the PCM middle layer when the | |
3002 | buffer position goes across the prescribed period size. To | |
3f03f7c5 | 3003 | inform this, call the <function>snd_pcm_period_elapsed()</function> |
1da177e4 LT |
3004 | function. |
3005 | </para> | |
3006 | ||
3007 | <para> | |
3008 | There are several types of sound chips to generate the interrupts. | |
3009 | </para> | |
3010 | ||
3011 | <section id="pcm-interface-interrupt-handler-boundary"> | |
3012 | <title>Interrupts at the period (fragment) boundary</title> | |
3013 | <para> | |
3014 | This is the most frequently found type: the hardware | |
3015 | generates an interrupt at each period boundary. | |
3016 | In this case, you can call | |
3017 | <function>snd_pcm_period_elapsed()</function> at each | |
3018 | interrupt. | |
3019 | </para> | |
3020 | ||
3021 | <para> | |
3022 | <function>snd_pcm_period_elapsed()</function> takes the | |
3023 | substream pointer as its argument. Thus, you need to keep the | |
3024 | substream pointer accessible from the chip instance. For | |
3025 | example, define substream field in the chip record to hold the | |
3026 | current running substream pointer, and set the pointer value | |
3027 | at open callback (and reset at close callback). | |
3028 | </para> | |
3029 | ||
3030 | <para> | |
0418726b | 3031 | If you acquire a spinlock in the interrupt handler, and the |
1da177e4 LT |
3032 | lock is used in other pcm callbacks, too, then you have to |
3033 | release the lock before calling | |
3034 | <function>snd_pcm_period_elapsed()</function>, because | |
3035 | <function>snd_pcm_period_elapsed()</function> calls other pcm | |
3036 | callbacks inside. | |
3037 | </para> | |
3038 | ||
3039 | <para> | |
3f03f7c5 | 3040 | Typical code would be like: |
1da177e4 LT |
3041 | |
3042 | <example> | |
3043 | <title>Interrupt Handler Case #1</title> | |
3044 | <programlisting> | |
3045 | <![CDATA[ | |
ad4d1dea | 3046 | static irqreturn_t snd_mychip_interrupt(int irq, void *dev_id) |
1da177e4 | 3047 | { |
446ab5f5 | 3048 | struct mychip *chip = dev_id; |
1da177e4 LT |
3049 | spin_lock(&chip->lock); |
3050 | .... | |
3051 | if (pcm_irq_invoked(chip)) { | |
3052 | /* call updater, unlock before it */ | |
3053 | spin_unlock(&chip->lock); | |
3054 | snd_pcm_period_elapsed(chip->substream); | |
3055 | spin_lock(&chip->lock); | |
95a5b085 | 3056 | /* acknowledge the interrupt if necessary */ |
1da177e4 LT |
3057 | } |
3058 | .... | |
3059 | spin_unlock(&chip->lock); | |
3060 | return IRQ_HANDLED; | |
3061 | } | |
3062 | ]]> | |
3063 | </programlisting> | |
3064 | </example> | |
3065 | </para> | |
3066 | </section> | |
3067 | ||
3068 | <section id="pcm-interface-interrupt-handler-timer"> | |
3f03f7c5 | 3069 | <title>High frequency timer interrupts</title> |
1da177e4 | 3070 | <para> |
d4dab5ab | 3071 | This happens when the hardware doesn't generate interrupts |
3f03f7c5 | 3072 | at the period boundary but issues timer interrupts at a fixed |
1da177e4 LT |
3073 | timer rate (e.g. es1968 or ymfpci drivers). |
3074 | In this case, you need to check the current hardware | |
3f03f7c5 MO |
3075 | position and accumulate the processed sample length at each |
3076 | interrupt. When the accumulated size exceeds the period | |
1da177e4 LT |
3077 | size, call |
3078 | <function>snd_pcm_period_elapsed()</function> and reset the | |
3079 | accumulator. | |
3080 | </para> | |
3081 | ||
3082 | <para> | |
3f03f7c5 | 3083 | Typical code would be like the following. |
1da177e4 LT |
3084 | |
3085 | <example> | |
3086 | <title>Interrupt Handler Case #2</title> | |
3087 | <programlisting> | |
3088 | <![CDATA[ | |
ad4d1dea | 3089 | static irqreturn_t snd_mychip_interrupt(int irq, void *dev_id) |
1da177e4 | 3090 | { |
446ab5f5 | 3091 | struct mychip *chip = dev_id; |
1da177e4 LT |
3092 | spin_lock(&chip->lock); |
3093 | .... | |
3094 | if (pcm_irq_invoked(chip)) { | |
3095 | unsigned int last_ptr, size; | |
3096 | /* get the current hardware pointer (in frames) */ | |
3097 | last_ptr = get_hw_ptr(chip); | |
3098 | /* calculate the processed frames since the | |
3099 | * last update | |
3100 | */ | |
3101 | if (last_ptr < chip->last_ptr) | |
3102 | size = runtime->buffer_size + last_ptr | |
3103 | - chip->last_ptr; | |
3104 | else | |
3105 | size = last_ptr - chip->last_ptr; | |
3106 | /* remember the last updated point */ | |
3107 | chip->last_ptr = last_ptr; | |
3108 | /* accumulate the size */ | |
3109 | chip->size += size; | |
3110 | /* over the period boundary? */ | |
3111 | if (chip->size >= runtime->period_size) { | |
3112 | /* reset the accumulator */ | |
3113 | chip->size %= runtime->period_size; | |
3114 | /* call updater */ | |
3115 | spin_unlock(&chip->lock); | |
3116 | snd_pcm_period_elapsed(substream); | |
3117 | spin_lock(&chip->lock); | |
3118 | } | |
95a5b085 | 3119 | /* acknowledge the interrupt if necessary */ |
1da177e4 LT |
3120 | } |
3121 | .... | |
3122 | spin_unlock(&chip->lock); | |
3123 | return IRQ_HANDLED; | |
3124 | } | |
3125 | ]]> | |
3126 | </programlisting> | |
3127 | </example> | |
3128 | </para> | |
3129 | </section> | |
3130 | ||
3131 | <section id="pcm-interface-interrupt-handler-both"> | |
3132 | <title>On calling <function>snd_pcm_period_elapsed()</function></title> | |
3133 | <para> | |
3134 | In both cases, even if more than one period are elapsed, you | |
3135 | don't have to call | |
3136 | <function>snd_pcm_period_elapsed()</function> many times. Call | |
3137 | only once. And the pcm layer will check the current hardware | |
3138 | pointer and update to the latest status. | |
3139 | </para> | |
3140 | </section> | |
3141 | </section> | |
3142 | ||
3143 | <section id="pcm-interface-atomicity"> | |
3144 | <title>Atomicity</title> | |
3145 | <para> | |
3f03f7c5 MO |
3146 | One of the most important (and thus difficult to debug) problems |
3147 | in kernel programming are race conditions. | |
3148 | In the Linux kernel, they are usually avoided via spin-locks, mutexes | |
3149 | or semaphores. In general, if a race condition can happen | |
3150 | in an interrupt handler, it has to be managed atomically, and you | |
3151 | have to use a spinlock to protect the critical session. If the | |
3152 | critical section is not in interrupt handler code and | |
3153 | if taking a relatively long time to execute is acceptable, you | |
3154 | should use mutexes or semaphores instead. | |
1da177e4 LT |
3155 | </para> |
3156 | ||
3157 | <para> | |
3158 | As already seen, some pcm callbacks are atomic and some are | |
3f03f7c5 | 3159 | not. For example, the <parameter>hw_params</parameter> callback is |
1da177e4 LT |
3160 | non-atomic, while <parameter>trigger</parameter> callback is |
3161 | atomic. This means, the latter is called already in a spinlock | |
3162 | held by the PCM middle layer. Please take this atomicity into | |
3f03f7c5 | 3163 | account when you choose a locking scheme in the callbacks. |
1da177e4 LT |
3164 | </para> |
3165 | ||
3166 | <para> | |
3167 | In the atomic callbacks, you cannot use functions which may call | |
3168 | <function>schedule</function> or go to | |
3f03f7c5 | 3169 | <function>sleep</function>. Semaphores and mutexes can sleep, |
1da177e4 LT |
3170 | and hence they cannot be used inside the atomic callbacks |
3171 | (e.g. <parameter>trigger</parameter> callback). | |
3f03f7c5 | 3172 | To implement some delay in such a callback, please use |
1da177e4 LT |
3173 | <function>udelay()</function> or <function>mdelay()</function>. |
3174 | </para> | |
3175 | ||
3176 | <para> | |
3177 | All three atomic callbacks (trigger, pointer, and ack) are | |
3178 | called with local interrupts disabled. | |
3179 | </para> | |
3180 | ||
941a74ca TI |
3181 | <para> |
3182 | The recent changes in PCM core code, however, allow all PCM | |
3183 | operations to be non-atomic. This assumes that the all caller | |
3184 | sides are in non-atomic contexts. For example, the function | |
3185 | <function>snd_pcm_period_elapsed()</function> is called | |
3186 | typically from the interrupt handler. But, if you set up the | |
3187 | driver to use a threaded interrupt handler, this call can be in | |
3188 | non-atomic context, too. In such a case, you can set | |
3189 | <structfield>nonatomic</structfield> filed of | |
3190 | <structname>snd_pcm</structname> object after creating it. | |
3191 | When this flag is set, mutex and rwsem are used internally in | |
3192 | the PCM core instead of spin and rwlocks, so that you can call | |
3193 | all PCM functions safely in a non-atomic context. | |
3194 | </para> | |
3195 | ||
1da177e4 LT |
3196 | </section> |
3197 | <section id="pcm-interface-constraints"> | |
3198 | <title>Constraints</title> | |
3199 | <para> | |
3200 | If your chip supports unconventional sample rates, or only the | |
3201 | limited samples, you need to set a constraint for the | |
3202 | condition. | |
3203 | </para> | |
3204 | ||
3205 | <para> | |
3206 | For example, in order to restrict the sample rates in the some | |
3207 | supported values, use | |
3208 | <function>snd_pcm_hw_constraint_list()</function>. | |
3209 | You need to call this function in the open callback. | |
3210 | ||
3211 | <example> | |
3212 | <title>Example of Hardware Constraints</title> | |
3213 | <programlisting> | |
3214 | <![CDATA[ | |
3215 | static unsigned int rates[] = | |
3216 | {4000, 10000, 22050, 44100}; | |
446ab5f5 | 3217 | static struct snd_pcm_hw_constraint_list constraints_rates = { |
1da177e4 LT |
3218 | .count = ARRAY_SIZE(rates), |
3219 | .list = rates, | |
3220 | .mask = 0, | |
3221 | }; | |
3222 | ||
446ab5f5 | 3223 | static int snd_mychip_pcm_open(struct snd_pcm_substream *substream) |
1da177e4 LT |
3224 | { |
3225 | int err; | |
3226 | .... | |
3227 | err = snd_pcm_hw_constraint_list(substream->runtime, 0, | |
3228 | SNDRV_PCM_HW_PARAM_RATE, | |
3229 | &constraints_rates); | |
3230 | if (err < 0) | |
3231 | return err; | |
3232 | .... | |
3233 | } | |
3234 | ]]> | |
3235 | </programlisting> | |
3236 | </example> | |
3237 | </para> | |
3238 | ||
3239 | <para> | |
3240 | There are many different constraints. | |
3f03f7c5 | 3241 | Look at <filename>sound/pcm.h</filename> for a complete list. |
1da177e4 LT |
3242 | You can even define your own constraint rules. |
3243 | For example, let's suppose my_chip can manage a substream of 1 channel | |
3244 | if and only if the format is S16_LE, otherwise it supports any format | |
5bda9fa1 | 3245 | specified in the <structname>snd_pcm_hardware</structname> structure (or in any |
1da177e4 LT |
3246 | other constraint_list). You can build a rule like this: |
3247 | ||
3248 | <example> | |
3249 | <title>Example of Hardware Constraints for Channels</title> | |
3250 | <programlisting> | |
3251 | <![CDATA[ | |
a690a2a1 | 3252 | static int hw_rule_channels_by_format(struct snd_pcm_hw_params *params, |
446ab5f5 | 3253 | struct snd_pcm_hw_rule *rule) |
1da177e4 | 3254 | { |
446ab5f5 | 3255 | struct snd_interval *c = hw_param_interval(params, |
a690a2a1 | 3256 | SNDRV_PCM_HW_PARAM_CHANNELS); |
446ab5f5 | 3257 | struct snd_mask *f = hw_param_mask(params, SNDRV_PCM_HW_PARAM_FORMAT); |
a690a2a1 | 3258 | struct snd_interval ch; |
1da177e4 | 3259 | |
a690a2a1 TI |
3260 | snd_interval_any(&ch); |
3261 | if (f->bits[0] == SNDRV_PCM_FMTBIT_S16_LE) { | |
3262 | ch.min = ch.max = 1; | |
3263 | ch.integer = 1; | |
3264 | return snd_interval_refine(c, &ch); | |
1da177e4 LT |
3265 | } |
3266 | return 0; | |
3267 | } | |
3268 | ]]> | |
3269 | </programlisting> | |
3270 | </example> | |
3271 | </para> | |
3272 | ||
3273 | <para> | |
3274 | Then you need to call this function to add your rule: | |
3275 | ||
3276 | <informalexample> | |
3277 | <programlisting> | |
3278 | <![CDATA[ | |
3279 | snd_pcm_hw_rule_add(substream->runtime, 0, SNDRV_PCM_HW_PARAM_CHANNELS, | |
16c5ab1d TI |
3280 | hw_rule_channels_by_format, NULL, |
3281 | SNDRV_PCM_HW_PARAM_FORMAT, -1); | |
1da177e4 LT |
3282 | ]]> |
3283 | </programlisting> | |
3284 | </informalexample> | |
3285 | </para> | |
3286 | ||
3287 | <para> | |
a690a2a1 TI |
3288 | The rule function is called when an application sets the PCM |
3289 | format, and it refines the number of channels accordingly. | |
3290 | But an application may set the number of channels before | |
3291 | setting the format. Thus you also need to define the inverse rule: | |
1da177e4 LT |
3292 | |
3293 | <example> | |
a690a2a1 | 3294 | <title>Example of Hardware Constraints for Formats</title> |
1da177e4 LT |
3295 | <programlisting> |
3296 | <![CDATA[ | |
a690a2a1 | 3297 | static int hw_rule_format_by_channels(struct snd_pcm_hw_params *params, |
446ab5f5 | 3298 | struct snd_pcm_hw_rule *rule) |
1da177e4 | 3299 | { |
446ab5f5 | 3300 | struct snd_interval *c = hw_param_interval(params, |
a690a2a1 | 3301 | SNDRV_PCM_HW_PARAM_CHANNELS); |
446ab5f5 | 3302 | struct snd_mask *f = hw_param_mask(params, SNDRV_PCM_HW_PARAM_FORMAT); |
a690a2a1 | 3303 | struct snd_mask fmt; |
1da177e4 | 3304 | |
a690a2a1 TI |
3305 | snd_mask_any(&fmt); /* Init the struct */ |
3306 | if (c->min < 2) { | |
3307 | fmt.bits[0] &= SNDRV_PCM_FMTBIT_S16_LE; | |
3308 | return snd_mask_refine(f, &fmt); | |
1da177e4 LT |
3309 | } |
3310 | return 0; | |
3311 | } | |
3312 | ]]> | |
3313 | </programlisting> | |
3314 | </example> | |
3315 | </para> | |
3316 | ||
3317 | <para> | |
3318 | ...and in the open callback: | |
3319 | <informalexample> | |
3320 | <programlisting> | |
3321 | <![CDATA[ | |
3322 | snd_pcm_hw_rule_add(substream->runtime, 0, SNDRV_PCM_HW_PARAM_FORMAT, | |
16c5ab1d TI |
3323 | hw_rule_format_by_channels, NULL, |
3324 | SNDRV_PCM_HW_PARAM_CHANNELS, -1); | |
1da177e4 LT |
3325 | ]]> |
3326 | </programlisting> | |
3327 | </informalexample> | |
3328 | </para> | |
3329 | ||
3330 | <para> | |
3f03f7c5 | 3331 | I won't give more details here, rather I |
1da177e4 LT |
3332 | would like to say, <quote>Luke, use the source.</quote> |
3333 | </para> | |
3334 | </section> | |
3335 | ||
3336 | </chapter> | |
3337 | ||
3338 | ||
3339 | <!-- ****************************************************** --> | |
3340 | <!-- Control Interface --> | |
3341 | <!-- ****************************************************** --> | |
3342 | <chapter id="control-interface"> | |
3343 | <title>Control Interface</title> | |
3344 | ||
3345 | <section id="control-interface-general"> | |
3346 | <title>General</title> | |
3347 | <para> | |
3348 | The control interface is used widely for many switches, | |
3f03f7c5 MO |
3349 | sliders, etc. which are accessed from user-space. Its most |
3350 | important use is the mixer interface. In other words, since ALSA | |
3351 | 0.9.x, all the mixer stuff is implemented on the control kernel API. | |
1da177e4 LT |
3352 | </para> |
3353 | ||
3354 | <para> | |
3355 | ALSA has a well-defined AC97 control module. If your chip | |
3356 | supports only the AC97 and nothing else, you can skip this | |
3357 | section. | |
3358 | </para> | |
3359 | ||
3360 | <para> | |
3361 | The control API is defined in | |
3362 | <filename><sound/control.h></filename>. | |
3f03f7c5 | 3363 | Include this file if you want to add your own controls. |
1da177e4 LT |
3364 | </para> |
3365 | </section> | |
3366 | ||
3367 | <section id="control-interface-definition"> | |
3368 | <title>Definition of Controls</title> | |
3369 | <para> | |
3f03f7c5 MO |
3370 | To create a new control, you need to define the |
3371 | following three | |
1da177e4 LT |
3372 | callbacks: <structfield>info</structfield>, |
3373 | <structfield>get</structfield> and | |
3374 | <structfield>put</structfield>. Then, define a | |
446ab5f5 | 3375 | struct <structname>snd_kcontrol_new</structname> record, such as: |
1da177e4 LT |
3376 | |
3377 | <example> | |
3378 | <title>Definition of a Control</title> | |
3379 | <programlisting> | |
3380 | <![CDATA[ | |
090015ae | 3381 | static struct snd_kcontrol_new my_control = { |
1da177e4 LT |
3382 | .iface = SNDRV_CTL_ELEM_IFACE_MIXER, |
3383 | .name = "PCM Playback Switch", | |
3384 | .index = 0, | |
3385 | .access = SNDRV_CTL_ELEM_ACCESS_READWRITE, | |
0b7bed4e | 3386 | .private_value = 0xffff, |
1da177e4 LT |
3387 | .info = my_control_info, |
3388 | .get = my_control_get, | |
3389 | .put = my_control_put | |
3390 | }; | |
3391 | ]]> | |
3392 | </programlisting> | |
3393 | </example> | |
3394 | </para> | |
3395 | ||
1da177e4 | 3396 | <para> |
3f03f7c5 MO |
3397 | The <structfield>iface</structfield> field specifies the control |
3398 | type, <constant>SNDRV_CTL_ELEM_IFACE_XXX</constant>, which | |
67ed4161 CL |
3399 | is usually <constant>MIXER</constant>. |
3400 | Use <constant>CARD</constant> for global controls that are not | |
3401 | logically part of the mixer. | |
3402 | If the control is closely associated with some specific device on | |
3403 | the sound card, use <constant>HWDEP</constant>, | |
3404 | <constant>PCM</constant>, <constant>RAWMIDI</constant>, | |
3405 | <constant>TIMER</constant>, or <constant>SEQUENCER</constant>, and | |
3406 | specify the device number with the | |
3407 | <structfield>device</structfield> and | |
3408 | <structfield>subdevice</structfield> fields. | |
1da177e4 LT |
3409 | </para> |
3410 | ||
3411 | <para> | |
3412 | The <structfield>name</structfield> is the name identifier | |
3f03f7c5 | 3413 | string. Since ALSA 0.9.x, the control name is very important, |
1da177e4 LT |
3414 | because its role is classified from its name. There are |
3415 | pre-defined standard control names. The details are described in | |
3f03f7c5 MO |
3416 | the <link linkend="control-interface-control-names"><citetitle> |
3417 | Control Names</citetitle></link> subsection. | |
1da177e4 LT |
3418 | </para> |
3419 | ||
3420 | <para> | |
3421 | The <structfield>index</structfield> field holds the index number | |
3422 | of this control. If there are several different controls with | |
3423 | the same name, they can be distinguished by the index | |
3424 | number. This is the case when | |
3425 | several codecs exist on the card. If the index is zero, you can | |
3426 | omit the definition above. | |
3427 | </para> | |
3428 | ||
3429 | <para> | |
3430 | The <structfield>access</structfield> field contains the access | |
3431 | type of this control. Give the combination of bit masks, | |
3432 | <constant>SNDRV_CTL_ELEM_ACCESS_XXX</constant>, there. | |
3f03f7c5 MO |
3433 | The details will be explained in |
3434 | the <link linkend="control-interface-access-flags"><citetitle> | |
3435 | Access Flags</citetitle></link> subsection. | |
1da177e4 LT |
3436 | </para> |
3437 | ||
3438 | <para> | |
0b7bed4e | 3439 | The <structfield>private_value</structfield> field contains |
1da177e4 | 3440 | an arbitrary long integer value for this record. When using |
3f03f7c5 | 3441 | the generic <structfield>info</structfield>, |
1da177e4 LT |
3442 | <structfield>get</structfield> and |
3443 | <structfield>put</structfield> callbacks, you can pass a value | |
3444 | through this field. If several small numbers are necessary, you can | |
3445 | combine them in bitwise. Or, it's possible to give a pointer | |
3446 | (casted to unsigned long) of some record to this field, too. | |
3447 | </para> | |
3448 | ||
d1761d1b CL |
3449 | <para> |
3450 | The <structfield>tlv</structfield> field can be used to provide | |
3451 | metadata about the control; see the | |
3452 | <link linkend="control-interface-tlv"> | |
3453 | <citetitle>Metadata</citetitle></link> subsection. | |
3454 | </para> | |
3455 | ||
1da177e4 LT |
3456 | <para> |
3457 | The other three are | |
3458 | <link linkend="control-interface-callbacks"><citetitle> | |
3459 | callback functions</citetitle></link>. | |
3460 | </para> | |
3461 | </section> | |
3462 | ||
3463 | <section id="control-interface-control-names"> | |
3464 | <title>Control Names</title> | |
3465 | <para> | |
3f03f7c5 | 3466 | There are some standards to define the control names. A |
1da177e4 LT |
3467 | control is usually defined from the three parts as |
3468 | <quote>SOURCE DIRECTION FUNCTION</quote>. | |
3469 | </para> | |
3470 | ||
3471 | <para> | |
3472 | The first, <constant>SOURCE</constant>, specifies the source | |
3473 | of the control, and is a string such as <quote>Master</quote>, | |
3f03f7c5 | 3474 | <quote>PCM</quote>, <quote>CD</quote> and |
1da177e4 LT |
3475 | <quote>Line</quote>. There are many pre-defined sources. |
3476 | </para> | |
3477 | ||
3478 | <para> | |
3479 | The second, <constant>DIRECTION</constant>, is one of the | |
3480 | following strings according to the direction of the control: | |
3481 | <quote>Playback</quote>, <quote>Capture</quote>, <quote>Bypass | |
3482 | Playback</quote> and <quote>Bypass Capture</quote>. Or, it can | |
3483 | be omitted, meaning both playback and capture directions. | |
3484 | </para> | |
3485 | ||
3486 | <para> | |
3487 | The third, <constant>FUNCTION</constant>, is one of the | |
3488 | following strings according to the function of the control: | |
3489 | <quote>Switch</quote>, <quote>Volume</quote> and | |
3490 | <quote>Route</quote>. | |
3491 | </para> | |
3492 | ||
3493 | <para> | |
3494 | The example of control names are, thus, <quote>Master Capture | |
3495 | Switch</quote> or <quote>PCM Playback Volume</quote>. | |
3496 | </para> | |
3497 | ||
3498 | <para> | |
3499 | There are some exceptions: | |
3500 | </para> | |
3501 | ||
3502 | <section id="control-interface-control-names-global"> | |
3503 | <title>Global capture and playback</title> | |
3504 | <para> | |
3505 | <quote>Capture Source</quote>, <quote>Capture Switch</quote> | |
3506 | and <quote>Capture Volume</quote> are used for the global | |
3507 | capture (input) source, switch and volume. Similarly, | |
3508 | <quote>Playback Switch</quote> and <quote>Playback | |
3509 | Volume</quote> are used for the global output gain switch and | |
3510 | volume. | |
3511 | </para> | |
3512 | </section> | |
3513 | ||
3514 | <section id="control-interface-control-names-tone"> | |
3515 | <title>Tone-controls</title> | |
3516 | <para> | |
3517 | tone-control switch and volumes are specified like | |
3518 | <quote>Tone Control - XXX</quote>, e.g. <quote>Tone Control - | |
3519 | Switch</quote>, <quote>Tone Control - Bass</quote>, | |
3520 | <quote>Tone Control - Center</quote>. | |
3521 | </para> | |
3522 | </section> | |
3523 | ||
3524 | <section id="control-interface-control-names-3d"> | |
3525 | <title>3D controls</title> | |
3526 | <para> | |
3527 | 3D-control switches and volumes are specified like <quote>3D | |
3528 | Control - XXX</quote>, e.g. <quote>3D Control - | |
3529 | Switch</quote>, <quote>3D Control - Center</quote>, <quote>3D | |
3530 | Control - Space</quote>. | |
3531 | </para> | |
3532 | </section> | |
3533 | ||
3534 | <section id="control-interface-control-names-mic"> | |
3535 | <title>Mic boost</title> | |
3536 | <para> | |
3537 | Mic-boost switch is set as <quote>Mic Boost</quote> or | |
3538 | <quote>Mic Boost (6dB)</quote>. | |
3539 | </para> | |
3540 | ||
3541 | <para> | |
3542 | More precise information can be found in | |
3543 | <filename>Documentation/sound/alsa/ControlNames.txt</filename>. | |
3544 | </para> | |
3545 | </section> | |
3546 | </section> | |
3547 | ||
3548 | <section id="control-interface-access-flags"> | |
3549 | <title>Access Flags</title> | |
3550 | ||
3551 | <para> | |
3f03f7c5 | 3552 | The access flag is the bitmask which specifies the access type |
1da177e4 LT |
3553 | of the given control. The default access type is |
3554 | <constant>SNDRV_CTL_ELEM_ACCESS_READWRITE</constant>, | |
3555 | which means both read and write are allowed to this control. | |
3556 | When the access flag is omitted (i.e. = 0), it is | |
3f03f7c5 | 3557 | considered as <constant>READWRITE</constant> access as default. |
1da177e4 LT |
3558 | </para> |
3559 | ||
3560 | <para> | |
3561 | When the control is read-only, pass | |
3562 | <constant>SNDRV_CTL_ELEM_ACCESS_READ</constant> instead. | |
3563 | In this case, you don't have to define | |
3f03f7c5 | 3564 | the <structfield>put</structfield> callback. |
1da177e4 | 3565 | Similarly, when the control is write-only (although it's a rare |
3f03f7c5 MO |
3566 | case), you can use the <constant>WRITE</constant> flag instead, and |
3567 | you don't need the <structfield>get</structfield> callback. | |
1da177e4 LT |
3568 | </para> |
3569 | ||
3570 | <para> | |
3571 | If the control value changes frequently (e.g. the VU meter), | |
3572 | <constant>VOLATILE</constant> flag should be given. This means | |
3573 | that the control may be changed without | |
3574 | <link linkend="control-interface-change-notification"><citetitle> | |
3f03f7c5 | 3575 | notification</citetitle></link>. Applications should poll such |
1da177e4 LT |
3576 | a control constantly. |
3577 | </para> | |
3578 | ||
3579 | <para> | |
3580 | When the control is inactive, set | |
3f03f7c5 | 3581 | the <constant>INACTIVE</constant> flag, too. |
1da177e4 | 3582 | There are <constant>LOCK</constant> and |
3f03f7c5 | 3583 | <constant>OWNER</constant> flags to change the write |
1da177e4 LT |
3584 | permissions. |
3585 | </para> | |
3586 | ||
3587 | </section> | |
3588 | ||
3589 | <section id="control-interface-callbacks"> | |
3590 | <title>Callbacks</title> | |
3591 | ||
3592 | <section id="control-interface-callbacks-info"> | |
3593 | <title>info callback</title> | |
3594 | <para> | |
3595 | The <structfield>info</structfield> callback is used to get | |
3f03f7c5 | 3596 | detailed information on this control. This must store the |
446ab5f5 | 3597 | values of the given struct <structname>snd_ctl_elem_info</structname> |
1da177e4 | 3598 | object. For example, for a boolean control with a single |
3f03f7c5 | 3599 | element: |
1da177e4 LT |
3600 | |
3601 | <example> | |
3602 | <title>Example of info callback</title> | |
3603 | <programlisting> | |
3604 | <![CDATA[ | |
95a5b085 | 3605 | static int snd_myctl_mono_info(struct snd_kcontrol *kcontrol, |
446ab5f5 | 3606 | struct snd_ctl_elem_info *uinfo) |
1da177e4 LT |
3607 | { |
3608 | uinfo->type = SNDRV_CTL_ELEM_TYPE_BOOLEAN; | |
3609 | uinfo->count = 1; | |
3610 | uinfo->value.integer.min = 0; | |
3611 | uinfo->value.integer.max = 1; | |
3612 | return 0; | |
3613 | } | |
3614 | ]]> | |
3615 | </programlisting> | |
3616 | </example> | |
3617 | </para> | |
3618 | ||
3619 | <para> | |
3620 | The <structfield>type</structfield> field specifies the type | |
3621 | of the control. There are <constant>BOOLEAN</constant>, | |
3622 | <constant>INTEGER</constant>, <constant>ENUMERATED</constant>, | |
3623 | <constant>BYTES</constant>, <constant>IEC958</constant> and | |
3624 | <constant>INTEGER64</constant>. The | |
3625 | <structfield>count</structfield> field specifies the | |
3626 | number of elements in this control. For example, a stereo | |
3627 | volume would have count = 2. The | |
3628 | <structfield>value</structfield> field is a union, and | |
3629 | the values stored are depending on the type. The boolean and | |
3f03f7c5 | 3630 | integer types are identical. |
1da177e4 LT |
3631 | </para> |
3632 | ||
3633 | <para> | |
3634 | The enumerated type is a bit different from others. You'll | |
3635 | need to set the string for the currently given item index. | |
3636 | ||
3637 | <informalexample> | |
3638 | <programlisting> | |
3639 | <![CDATA[ | |
95a5b085 | 3640 | static int snd_myctl_enum_info(struct snd_kcontrol *kcontrol, |
446ab5f5 | 3641 | struct snd_ctl_elem_info *uinfo) |
1da177e4 LT |
3642 | { |
3643 | static char *texts[4] = { | |
3644 | "First", "Second", "Third", "Fourth" | |
3645 | }; | |
3646 | uinfo->type = SNDRV_CTL_ELEM_TYPE_ENUMERATED; | |
3647 | uinfo->count = 1; | |
3648 | uinfo->value.enumerated.items = 4; | |
3649 | if (uinfo->value.enumerated.item > 3) | |
3650 | uinfo->value.enumerated.item = 3; | |
3651 | strcpy(uinfo->value.enumerated.name, | |
3652 | texts[uinfo->value.enumerated.item]); | |
3653 | return 0; | |
3654 | } | |
3655 | ]]> | |
3656 | </programlisting> | |
3657 | </informalexample> | |
3658 | </para> | |
95a5b085 | 3659 | |
be93709c TI |
3660 | <para> |
3661 | The above callback can be simplified with a helper function, | |
3662 | <function>snd_ctl_enum_info</function>. The final code | |
3663 | looks like below. | |
3664 | (You can pass ARRAY_SIZE(texts) instead of 4 in the third | |
3665 | argument; it's a matter of taste.) | |
3666 | ||
3667 | <informalexample> | |
3668 | <programlisting> | |
3669 | <![CDATA[ | |
3670 | static int snd_myctl_enum_info(struct snd_kcontrol *kcontrol, | |
3671 | struct snd_ctl_elem_info *uinfo) | |
3672 | { | |
3673 | static char *texts[4] = { | |
3674 | "First", "Second", "Third", "Fourth" | |
3675 | }; | |
3676 | return snd_ctl_enum_info(uinfo, 1, 4, texts); | |
3677 | } | |
3678 | ]]> | |
3679 | </programlisting> | |
3680 | </informalexample> | |
3681 | </para> | |
3682 | ||
95a5b085 | 3683 | <para> |
3f03f7c5 | 3684 | Some common info callbacks are available for your convenience: |
95a5b085 TI |
3685 | <function>snd_ctl_boolean_mono_info()</function> and |
3686 | <function>snd_ctl_boolean_stereo_info()</function>. | |
3687 | Obviously, the former is an info callback for a mono channel | |
3688 | boolean item, just like <function>snd_myctl_mono_info</function> | |
3689 | above, and the latter is for a stereo channel boolean item. | |
3690 | </para> | |
3691 | ||
1da177e4 LT |
3692 | </section> |
3693 | ||
3694 | <section id="control-interface-callbacks-get"> | |
3695 | <title>get callback</title> | |
3696 | ||
3697 | <para> | |
3698 | This callback is used to read the current value of the | |
3f03f7c5 | 3699 | control and to return to user-space. |
1da177e4 LT |
3700 | </para> |
3701 | ||
3702 | <para> | |
3703 | For example, | |
3704 | ||
3705 | <example> | |
3706 | <title>Example of get callback</title> | |
3707 | <programlisting> | |
3708 | <![CDATA[ | |
446ab5f5 TI |
3709 | static int snd_myctl_get(struct snd_kcontrol *kcontrol, |
3710 | struct snd_ctl_elem_value *ucontrol) | |
1da177e4 | 3711 | { |
446ab5f5 | 3712 | struct mychip *chip = snd_kcontrol_chip(kcontrol); |
1da177e4 LT |
3713 | ucontrol->value.integer.value[0] = get_some_value(chip); |
3714 | return 0; | |
3715 | } | |
3716 | ]]> | |
3717 | </programlisting> | |
3718 | </example> | |
3719 | </para> | |
3720 | ||
1da177e4 | 3721 | <para> |
3f03f7c5 MO |
3722 | The <structfield>value</structfield> field depends on |
3723 | the type of control as well as on the info callback. For example, | |
1da177e4 LT |
3724 | the sb driver uses this field to store the register offset, |
3725 | the bit-shift and the bit-mask. The | |
3f03f7c5 | 3726 | <structfield>private_value</structfield> field is set as follows: |
1da177e4 LT |
3727 | <informalexample> |
3728 | <programlisting> | |
3729 | <![CDATA[ | |
3730 | .private_value = reg | (shift << 16) | (mask << 24) | |
3731 | ]]> | |
3732 | </programlisting> | |
3733 | </informalexample> | |
3734 | and is retrieved in callbacks like | |
3735 | <informalexample> | |
3736 | <programlisting> | |
3737 | <![CDATA[ | |
446ab5f5 TI |
3738 | static int snd_sbmixer_get_single(struct snd_kcontrol *kcontrol, |
3739 | struct snd_ctl_elem_value *ucontrol) | |
1da177e4 LT |
3740 | { |
3741 | int reg = kcontrol->private_value & 0xff; | |
3742 | int shift = (kcontrol->private_value >> 16) & 0xff; | |
3743 | int mask = (kcontrol->private_value >> 24) & 0xff; | |
3744 | .... | |
3745 | } | |
3746 | ]]> | |
3747 | </programlisting> | |
3748 | </informalexample> | |
3749 | </para> | |
3750 | ||
3751 | <para> | |
3f03f7c5 MO |
3752 | In the <structfield>get</structfield> callback, |
3753 | you have to fill all the elements if the | |
1da177e4 LT |
3754 | control has more than one elements, |
3755 | i.e. <structfield>count</structfield> > 1. | |
3756 | In the example above, we filled only one element | |
3757 | (<structfield>value.integer.value[0]</structfield>) since it's | |
3758 | assumed as <structfield>count</structfield> = 1. | |
3759 | </para> | |
3760 | </section> | |
3761 | ||
3762 | <section id="control-interface-callbacks-put"> | |
3763 | <title>put callback</title> | |
3764 | ||
3765 | <para> | |
3f03f7c5 | 3766 | This callback is used to write a value from user-space. |
1da177e4 LT |
3767 | </para> |
3768 | ||
3769 | <para> | |
3770 | For example, | |
3771 | ||
3772 | <example> | |
3773 | <title>Example of put callback</title> | |
3774 | <programlisting> | |
3775 | <![CDATA[ | |
446ab5f5 TI |
3776 | static int snd_myctl_put(struct snd_kcontrol *kcontrol, |
3777 | struct snd_ctl_elem_value *ucontrol) | |
1da177e4 | 3778 | { |
446ab5f5 | 3779 | struct mychip *chip = snd_kcontrol_chip(kcontrol); |
1da177e4 LT |
3780 | int changed = 0; |
3781 | if (chip->current_value != | |
3782 | ucontrol->value.integer.value[0]) { | |
3783 | change_current_value(chip, | |
3784 | ucontrol->value.integer.value[0]); | |
3785 | changed = 1; | |
3786 | } | |
3787 | return changed; | |
3788 | } | |
3789 | ]]> | |
3790 | </programlisting> | |
3791 | </example> | |
3792 | ||
3793 | As seen above, you have to return 1 if the value is | |
3794 | changed. If the value is not changed, return 0 instead. | |
3795 | If any fatal error happens, return a negative error code as | |
3796 | usual. | |
3797 | </para> | |
3798 | ||
3799 | <para> | |
3f03f7c5 | 3800 | As in the <structfield>get</structfield> callback, |
1da177e4 | 3801 | when the control has more than one elements, |
5bda9fa1 | 3802 | all elements must be evaluated in this callback, too. |
1da177e4 LT |
3803 | </para> |
3804 | </section> | |
3805 | ||
3806 | <section id="control-interface-callbacks-all"> | |
3807 | <title>Callbacks are not atomic</title> | |
3808 | <para> | |
3809 | All these three callbacks are basically not atomic. | |
3810 | </para> | |
3811 | </section> | |
3812 | </section> | |
3813 | ||
3814 | <section id="control-interface-constructor"> | |
3815 | <title>Constructor</title> | |
3816 | <para> | |
3817 | When everything is ready, finally we can create a new | |
3f03f7c5 | 3818 | control. To create a control, there are two functions to be |
1da177e4 LT |
3819 | called, <function>snd_ctl_new1()</function> and |
3820 | <function>snd_ctl_add()</function>. | |
3821 | </para> | |
3822 | ||
3823 | <para> | |
3824 | In the simplest way, you can do like this: | |
3825 | ||
3826 | <informalexample> | |
3827 | <programlisting> | |
3828 | <![CDATA[ | |
95a5b085 TI |
3829 | err = snd_ctl_add(card, snd_ctl_new1(&my_control, chip)); |
3830 | if (err < 0) | |
1da177e4 LT |
3831 | return err; |
3832 | ]]> | |
3833 | </programlisting> | |
3834 | </informalexample> | |
3835 | ||
3836 | where <parameter>my_control</parameter> is the | |
446ab5f5 | 3837 | struct <structname>snd_kcontrol_new</structname> object defined above, and chip |
1da177e4 LT |
3838 | is the object pointer to be passed to |
3839 | kcontrol->private_data | |
3f03f7c5 | 3840 | which can be referred to in callbacks. |
1da177e4 LT |
3841 | </para> |
3842 | ||
3843 | <para> | |
3844 | <function>snd_ctl_new1()</function> allocates a new | |
090015ae TI |
3845 | <structname>snd_kcontrol</structname> instance, |
3846 | and <function>snd_ctl_add</function> assigns the given | |
1da177e4 LT |
3847 | control component to the card. |
3848 | </para> | |
3849 | </section> | |
3850 | ||
3851 | <section id="control-interface-change-notification"> | |
3852 | <title>Change Notification</title> | |
3853 | <para> | |
3854 | If you need to change and update a control in the interrupt | |
3855 | routine, you can call <function>snd_ctl_notify()</function>. For | |
3856 | example, | |
3857 | ||
3858 | <informalexample> | |
3859 | <programlisting> | |
3860 | <![CDATA[ | |
3861 | snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_VALUE, id_pointer); | |
3862 | ]]> | |
3863 | </programlisting> | |
3864 | </informalexample> | |
3865 | ||
3866 | This function takes the card pointer, the event-mask, and the | |
3867 | control id pointer for the notification. The event-mask | |
3868 | specifies the types of notification, for example, in the above | |
3869 | example, the change of control values is notified. | |
446ab5f5 | 3870 | The id pointer is the pointer of struct <structname>snd_ctl_elem_id</structname> |
1da177e4 LT |
3871 | to be notified. |
3872 | You can find some examples in <filename>es1938.c</filename> or | |
3873 | <filename>es1968.c</filename> for hardware volume interrupts. | |
3874 | </para> | |
3875 | </section> | |
3876 | ||
d1761d1b CL |
3877 | <section id="control-interface-tlv"> |
3878 | <title>Metadata</title> | |
3879 | <para> | |
3880 | To provide information about the dB values of a mixer control, use | |
3881 | on of the <constant>DECLARE_TLV_xxx</constant> macros from | |
3882 | <filename><sound/tlv.h></filename> to define a variable | |
3883 | containing this information, set the<structfield>tlv.p | |
3884 | </structfield> field to point to this variable, and include the | |
3885 | <constant>SNDRV_CTL_ELEM_ACCESS_TLV_READ</constant> flag in the | |
3886 | <structfield>access</structfield> field; like this: | |
3887 | <informalexample> | |
3888 | <programlisting> | |
3889 | <![CDATA[ | |
3890 | static DECLARE_TLV_DB_SCALE(db_scale_my_control, -4050, 150, 0); | |
3891 | ||
090015ae | 3892 | static struct snd_kcontrol_new my_control = { |
d1761d1b CL |
3893 | ... |
3894 | .access = SNDRV_CTL_ELEM_ACCESS_READWRITE | | |
3895 | SNDRV_CTL_ELEM_ACCESS_TLV_READ, | |
3896 | ... | |
3897 | .tlv.p = db_scale_my_control, | |
3898 | }; | |
3899 | ]]> | |
3900 | </programlisting> | |
3901 | </informalexample> | |
3902 | </para> | |
3903 | ||
3904 | <para> | |
3905 | The <function>DECLARE_TLV_DB_SCALE</function> macro defines | |
3906 | information about a mixer control where each step in the control's | |
3907 | value changes the dB value by a constant dB amount. | |
3908 | The first parameter is the name of the variable to be defined. | |
3909 | The second parameter is the minimum value, in units of 0.01 dB. | |
3910 | The third parameter is the step size, in units of 0.01 dB. | |
3911 | Set the fourth parameter to 1 if the minimum value actually mutes | |
3912 | the control. | |
3913 | </para> | |
3914 | ||
3915 | <para> | |
3916 | The <function>DECLARE_TLV_DB_LINEAR</function> macro defines | |
3917 | information about a mixer control where the control's value affects | |
3918 | the output linearly. | |
3919 | The first parameter is the name of the variable to be defined. | |
3920 | The second parameter is the minimum value, in units of 0.01 dB. | |
3921 | The third parameter is the maximum value, in units of 0.01 dB. | |
3922 | If the minimum value mutes the control, set the second parameter to | |
3923 | <constant>TLV_DB_GAIN_MUTE</constant>. | |
3924 | </para> | |
3925 | </section> | |
3926 | ||
1da177e4 LT |
3927 | </chapter> |
3928 | ||
3929 | ||
3930 | <!-- ****************************************************** --> | |
3931 | <!-- API for AC97 Codec --> | |
3932 | <!-- ****************************************************** --> | |
3933 | <chapter id="api-ac97"> | |
3934 | <title>API for AC97 Codec</title> | |
3935 | ||
3936 | <section> | |
3937 | <title>General</title> | |
3938 | <para> | |
3939 | The ALSA AC97 codec layer is a well-defined one, and you don't | |
3f03f7c5 | 3940 | have to write much code to control it. Only low-level control |
1da177e4 LT |
3941 | routines are necessary. The AC97 codec API is defined in |
3942 | <filename><sound/ac97_codec.h></filename>. | |
3943 | </para> | |
3944 | </section> | |
3945 | ||
3946 | <section id="api-ac97-example"> | |
3947 | <title>Full Code Example</title> | |
3948 | <para> | |
3949 | <example> | |
3950 | <title>Example of AC97 Interface</title> | |
3951 | <programlisting> | |
3952 | <![CDATA[ | |
446ab5f5 | 3953 | struct mychip { |
1da177e4 | 3954 | .... |
446ab5f5 | 3955 | struct snd_ac97 *ac97; |
1da177e4 LT |
3956 | .... |
3957 | }; | |
3958 | ||
446ab5f5 | 3959 | static unsigned short snd_mychip_ac97_read(struct snd_ac97 *ac97, |
1da177e4 LT |
3960 | unsigned short reg) |
3961 | { | |
446ab5f5 | 3962 | struct mychip *chip = ac97->private_data; |
1da177e4 | 3963 | .... |
95a5b085 | 3964 | /* read a register value here from the codec */ |
1da177e4 LT |
3965 | return the_register_value; |
3966 | } | |
3967 | ||
446ab5f5 | 3968 | static void snd_mychip_ac97_write(struct snd_ac97 *ac97, |
1da177e4 LT |
3969 | unsigned short reg, unsigned short val) |
3970 | { | |
446ab5f5 | 3971 | struct mychip *chip = ac97->private_data; |
1da177e4 | 3972 | .... |
95a5b085 | 3973 | /* write the given register value to the codec */ |
1da177e4 LT |
3974 | } |
3975 | ||
446ab5f5 | 3976 | static int snd_mychip_ac97(struct mychip *chip) |
1da177e4 | 3977 | { |
446ab5f5 TI |
3978 | struct snd_ac97_bus *bus; |
3979 | struct snd_ac97_template ac97; | |
1da177e4 | 3980 | int err; |
446ab5f5 | 3981 | static struct snd_ac97_bus_ops ops = { |
1da177e4 LT |
3982 | .write = snd_mychip_ac97_write, |
3983 | .read = snd_mychip_ac97_read, | |
3984 | }; | |
3985 | ||
95a5b085 TI |
3986 | err = snd_ac97_bus(chip->card, 0, &ops, NULL, &bus); |
3987 | if (err < 0) | |
1da177e4 LT |
3988 | return err; |
3989 | memset(&ac97, 0, sizeof(ac97)); | |
3990 | ac97.private_data = chip; | |
3991 | return snd_ac97_mixer(bus, &ac97, &chip->ac97); | |
3992 | } | |
3993 | ||
3994 | ]]> | |
3995 | </programlisting> | |
3996 | </example> | |
3997 | </para> | |
3998 | </section> | |
3999 | ||
4000 | <section id="api-ac97-constructor"> | |
4001 | <title>Constructor</title> | |
4002 | <para> | |
3f03f7c5 | 4003 | To create an ac97 instance, first call <function>snd_ac97_bus</function> |
1da177e4 LT |
4004 | with an <type>ac97_bus_ops_t</type> record with callback functions. |
4005 | ||
4006 | <informalexample> | |
4007 | <programlisting> | |
4008 | <![CDATA[ | |
446ab5f5 TI |
4009 | struct snd_ac97_bus *bus; |
4010 | static struct snd_ac97_bus_ops ops = { | |
1da177e4 LT |
4011 | .write = snd_mychip_ac97_write, |
4012 | .read = snd_mychip_ac97_read, | |
4013 | }; | |
4014 | ||
4015 | snd_ac97_bus(card, 0, &ops, NULL, &pbus); | |
4016 | ]]> | |
4017 | </programlisting> | |
4018 | </informalexample> | |
4019 | ||
4020 | The bus record is shared among all belonging ac97 instances. | |
4021 | </para> | |
4022 | ||
4023 | <para> | |
446ab5f5 TI |
4024 | And then call <function>snd_ac97_mixer()</function> with an |
4025 | struct <structname>snd_ac97_template</structname> | |
1da177e4 LT |
4026 | record together with the bus pointer created above. |
4027 | ||
4028 | <informalexample> | |
4029 | <programlisting> | |
4030 | <![CDATA[ | |
446ab5f5 | 4031 | struct snd_ac97_template ac97; |
1da177e4 LT |
4032 | int err; |
4033 | ||
4034 | memset(&ac97, 0, sizeof(ac97)); | |
4035 | ac97.private_data = chip; | |
4036 | snd_ac97_mixer(bus, &ac97, &chip->ac97); | |
4037 | ]]> | |
4038 | </programlisting> | |
4039 | </informalexample> | |
4040 | ||
3f03f7c5 | 4041 | where chip->ac97 is a pointer to a newly created |
1da177e4 LT |
4042 | <type>ac97_t</type> instance. |
4043 | In this case, the chip pointer is set as the private data, so that | |
4044 | the read/write callback functions can refer to this chip instance. | |
4045 | This instance is not necessarily stored in the chip | |
3f03f7c5 | 4046 | record. If you need to change the register values from the |
1da177e4 LT |
4047 | driver, or need the suspend/resume of ac97 codecs, keep this |
4048 | pointer to pass to the corresponding functions. | |
4049 | </para> | |
4050 | </section> | |
4051 | ||
4052 | <section id="api-ac97-callbacks"> | |
4053 | <title>Callbacks</title> | |
4054 | <para> | |
4055 | The standard callbacks are <structfield>read</structfield> and | |
4056 | <structfield>write</structfield>. Obviously they | |
4057 | correspond to the functions for read and write accesses to the | |
4058 | hardware low-level codes. | |
4059 | </para> | |
4060 | ||
4061 | <para> | |
4062 | The <structfield>read</structfield> callback returns the | |
4063 | register value specified in the argument. | |
4064 | ||
4065 | <informalexample> | |
4066 | <programlisting> | |
4067 | <![CDATA[ | |
446ab5f5 | 4068 | static unsigned short snd_mychip_ac97_read(struct snd_ac97 *ac97, |
1da177e4 LT |
4069 | unsigned short reg) |
4070 | { | |
446ab5f5 | 4071 | struct mychip *chip = ac97->private_data; |
1da177e4 LT |
4072 | .... |
4073 | return the_register_value; | |
4074 | } | |
4075 | ]]> | |
4076 | </programlisting> | |
4077 | </informalexample> | |
4078 | ||
4079 | Here, the chip can be cast from ac97->private_data. | |
4080 | </para> | |
4081 | ||
4082 | <para> | |
4083 | Meanwhile, the <structfield>write</structfield> callback is | |
4084 | used to set the register value. | |
4085 | ||
4086 | <informalexample> | |
4087 | <programlisting> | |
4088 | <![CDATA[ | |
446ab5f5 | 4089 | static void snd_mychip_ac97_write(struct snd_ac97 *ac97, |
1da177e4 LT |
4090 | unsigned short reg, unsigned short val) |
4091 | ]]> | |
4092 | </programlisting> | |
4093 | </informalexample> | |
4094 | </para> | |
4095 | ||
4096 | <para> | |
3f03f7c5 | 4097 | These callbacks are non-atomic like the control API callbacks. |
1da177e4 LT |
4098 | </para> |
4099 | ||
4100 | <para> | |
4101 | There are also other callbacks: | |
4102 | <structfield>reset</structfield>, | |
4103 | <structfield>wait</structfield> and | |
4104 | <structfield>init</structfield>. | |
4105 | </para> | |
4106 | ||
4107 | <para> | |
4108 | The <structfield>reset</structfield> callback is used to reset | |
3f03f7c5 | 4109 | the codec. If the chip requires a special kind of reset, you can |
1da177e4 LT |
4110 | define this callback. |
4111 | </para> | |
4112 | ||
4113 | <para> | |
3f03f7c5 MO |
4114 | The <structfield>wait</structfield> callback is used to |
4115 | add some waiting time in the standard initialization of the codec. If the | |
4116 | chip requires the extra waiting time, define this callback. | |
1da177e4 LT |
4117 | </para> |
4118 | ||
4119 | <para> | |
4120 | The <structfield>init</structfield> callback is used for | |
4121 | additional initialization of the codec. | |
4122 | </para> | |
4123 | </section> | |
4124 | ||
4125 | <section id="api-ac97-updating-registers"> | |
4126 | <title>Updating Registers in The Driver</title> | |
4127 | <para> | |
4128 | If you need to access to the codec from the driver, you can | |
4129 | call the following functions: | |
4130 | <function>snd_ac97_write()</function>, | |
4131 | <function>snd_ac97_read()</function>, | |
4132 | <function>snd_ac97_update()</function> and | |
4133 | <function>snd_ac97_update_bits()</function>. | |
4134 | </para> | |
4135 | ||
4136 | <para> | |
4137 | Both <function>snd_ac97_write()</function> and | |
4138 | <function>snd_ac97_update()</function> functions are used to | |
4139 | set a value to the given register | |
4140 | (<constant>AC97_XXX</constant>). The difference between them is | |
4141 | that <function>snd_ac97_update()</function> doesn't write a | |
4142 | value if the given value has been already set, while | |
4143 | <function>snd_ac97_write()</function> always rewrites the | |
4144 | value. | |
4145 | ||
4146 | <informalexample> | |
4147 | <programlisting> | |
4148 | <![CDATA[ | |
4149 | snd_ac97_write(ac97, AC97_MASTER, 0x8080); | |
4150 | snd_ac97_update(ac97, AC97_MASTER, 0x8080); | |
4151 | ]]> | |
4152 | </programlisting> | |
4153 | </informalexample> | |
4154 | </para> | |
4155 | ||
4156 | <para> | |
4157 | <function>snd_ac97_read()</function> is used to read the value | |
4158 | of the given register. For example, | |
4159 | ||
4160 | <informalexample> | |
4161 | <programlisting> | |
4162 | <![CDATA[ | |
4163 | value = snd_ac97_read(ac97, AC97_MASTER); | |
4164 | ]]> | |
4165 | </programlisting> | |
4166 | </informalexample> | |
4167 | </para> | |
4168 | ||
4169 | <para> | |
4170 | <function>snd_ac97_update_bits()</function> is used to update | |
3f03f7c5 | 4171 | some bits in the given register. |
1da177e4 LT |
4172 | |
4173 | <informalexample> | |
4174 | <programlisting> | |
4175 | <![CDATA[ | |
4176 | snd_ac97_update_bits(ac97, reg, mask, value); | |
4177 | ]]> | |
4178 | </programlisting> | |
4179 | </informalexample> | |
4180 | </para> | |
4181 | ||
4182 | <para> | |
4183 | Also, there is a function to change the sample rate (of a | |
3f03f7c5 | 4184 | given register such as |
1da177e4 LT |
4185 | <constant>AC97_PCM_FRONT_DAC_RATE</constant>) when VRA or |
4186 | DRA is supported by the codec: | |
4187 | <function>snd_ac97_set_rate()</function>. | |
4188 | ||
4189 | <informalexample> | |
4190 | <programlisting> | |
4191 | <![CDATA[ | |
4192 | snd_ac97_set_rate(ac97, AC97_PCM_FRONT_DAC_RATE, 44100); | |
4193 | ]]> | |
4194 | </programlisting> | |
4195 | </informalexample> | |
4196 | </para> | |
4197 | ||
4198 | <para> | |
3f03f7c5 | 4199 | The following registers are available to set the rate: |
1da177e4 LT |
4200 | <constant>AC97_PCM_MIC_ADC_RATE</constant>, |
4201 | <constant>AC97_PCM_FRONT_DAC_RATE</constant>, | |
4202 | <constant>AC97_PCM_LR_ADC_RATE</constant>, | |
3f03f7c5 | 4203 | <constant>AC97_SPDIF</constant>. When |
1da177e4 LT |
4204 | <constant>AC97_SPDIF</constant> is specified, the register is |
4205 | not really changed but the corresponding IEC958 status bits will | |
4206 | be updated. | |
4207 | </para> | |
4208 | </section> | |
4209 | ||
4210 | <section id="api-ac97-clock-adjustment"> | |
4211 | <title>Clock Adjustment</title> | |
4212 | <para> | |
3f03f7c5 | 4213 | In some chips, the clock of the codec isn't 48000 but using a |
1da177e4 LT |
4214 | PCI clock (to save a quartz!). In this case, change the field |
4215 | bus->clock to the corresponding | |
4216 | value. For example, intel8x0 | |
3f03f7c5 | 4217 | and es1968 drivers have their own function to read from the clock. |
1da177e4 LT |
4218 | </para> |
4219 | </section> | |
4220 | ||
4221 | <section id="api-ac97-proc-files"> | |
4222 | <title>Proc Files</title> | |
4223 | <para> | |
4224 | The ALSA AC97 interface will create a proc file such as | |
4225 | <filename>/proc/asound/card0/codec97#0/ac97#0-0</filename> and | |
4226 | <filename>ac97#0-0+regs</filename>. You can refer to these files to | |
4227 | see the current status and registers of the codec. | |
4228 | </para> | |
4229 | </section> | |
4230 | ||
4231 | <section id="api-ac97-multiple-codecs"> | |
4232 | <title>Multiple Codecs</title> | |
4233 | <para> | |
4234 | When there are several codecs on the same card, you need to | |
446ab5f5 | 4235 | call <function>snd_ac97_mixer()</function> multiple times with |
1da177e4 | 4236 | ac97.num=1 or greater. The <structfield>num</structfield> field |
3f03f7c5 | 4237 | specifies the codec number. |
1da177e4 LT |
4238 | </para> |
4239 | ||
4240 | <para> | |
3f03f7c5 | 4241 | If you set up multiple codecs, you either need to write |
1da177e4 | 4242 | different callbacks for each codec or check |
3f03f7c5 | 4243 | ac97->num in the callback routines. |
1da177e4 LT |
4244 | </para> |
4245 | </section> | |
4246 | ||
4247 | </chapter> | |
4248 | ||
4249 | ||
4250 | <!-- ****************************************************** --> | |
4251 | <!-- MIDI (MPU401-UART) Interface --> | |
4252 | <!-- ****************************************************** --> | |
4253 | <chapter id="midi-interface"> | |
4254 | <title>MIDI (MPU401-UART) Interface</title> | |
4255 | ||
4256 | <section id="midi-interface-general"> | |
4257 | <title>General</title> | |
4258 | <para> | |
4259 | Many soundcards have built-in MIDI (MPU401-UART) | |
4260 | interfaces. When the soundcard supports the standard MPU401-UART | |
4261 | interface, most likely you can use the ALSA MPU401-UART API. The | |
4262 | MPU401-UART API is defined in | |
4263 | <filename><sound/mpu401.h></filename>. | |
4264 | </para> | |
4265 | ||
4266 | <para> | |
3f03f7c5 | 4267 | Some soundchips have a similar but slightly different |
1da177e4 LT |
4268 | implementation of mpu401 stuff. For example, emu10k1 has its own |
4269 | mpu401 routines. | |
4270 | </para> | |
4271 | </section> | |
4272 | ||
4273 | <section id="midi-interface-constructor"> | |
4274 | <title>Constructor</title> | |
4275 | <para> | |
3f03f7c5 | 4276 | To create a rawmidi object, call |
1da177e4 LT |
4277 | <function>snd_mpu401_uart_new()</function>. |
4278 | ||
4279 | <informalexample> | |
4280 | <programlisting> | |
4281 | <![CDATA[ | |
446ab5f5 | 4282 | struct snd_rawmidi *rmidi; |
302e4c2f | 4283 | snd_mpu401_uart_new(card, 0, MPU401_HW_MPU401, port, info_flags, |
dba8b469 | 4284 | irq, &rmidi); |
1da177e4 LT |
4285 | ]]> |
4286 | </programlisting> | |
4287 | </informalexample> | |
4288 | </para> | |
4289 | ||
4290 | <para> | |
4291 | The first argument is the card pointer, and the second is the | |
4292 | index of this component. You can create up to 8 rawmidi | |
4293 | devices. | |
4294 | </para> | |
4295 | ||
4296 | <para> | |
4297 | The third argument is the type of the hardware, | |
4298 | <constant>MPU401_HW_XXX</constant>. If it's not a special one, | |
4299 | you can use <constant>MPU401_HW_MPU401</constant>. | |
4300 | </para> | |
4301 | ||
4302 | <para> | |
3f03f7c5 MO |
4303 | The 4th argument is the I/O port address. Many |
4304 | backward-compatible MPU401 have an I/O port such as 0x330. Or, it | |
4305 | might be a part of its own PCI I/O region. It depends on the | |
1da177e4 LT |
4306 | chip design. |
4307 | </para> | |
4308 | ||
4309 | <para> | |
3f03f7c5 MO |
4310 | The 5th argument is a bitflag for additional information. |
4311 | When the I/O port address above is part of the PCI I/O | |
4312 | region, the MPU401 I/O port might have been already allocated | |
302e4c2f TI |
4313 | (reserved) by the driver itself. In such a case, pass a bit flag |
4314 | <constant>MPU401_INFO_INTEGRATED</constant>, | |
3f03f7c5 | 4315 | and the mpu401-uart layer will allocate the I/O ports by itself. |
1da177e4 LT |
4316 | </para> |
4317 | ||
302e4c2f TI |
4318 | <para> |
4319 | When the controller supports only the input or output MIDI stream, | |
3f03f7c5 | 4320 | pass the <constant>MPU401_INFO_INPUT</constant> or |
302e4c2f TI |
4321 | <constant>MPU401_INFO_OUTPUT</constant> bitflag, respectively. |
4322 | Then the rawmidi instance is created as a single stream. | |
4323 | </para> | |
4324 | ||
4325 | <para> | |
4326 | <constant>MPU401_INFO_MMIO</constant> bitflag is used to change | |
4327 | the access method to MMIO (via readb and writeb) instead of | |
3f03f7c5 | 4328 | iob and outb. In this case, you have to pass the iomapped address |
302e4c2f TI |
4329 | to <function>snd_mpu401_uart_new()</function>. |
4330 | </para> | |
4331 | ||
4332 | <para> | |
4333 | When <constant>MPU401_INFO_TX_IRQ</constant> is set, the output | |
4334 | stream isn't checked in the default interrupt handler. The driver | |
4335 | needs to call <function>snd_mpu401_uart_interrupt_tx()</function> | |
3f03f7c5 | 4336 | by itself to start processing the output stream in the irq handler. |
302e4c2f TI |
4337 | </para> |
4338 | ||
dba8b469 CL |
4339 | <para> |
4340 | If the MPU-401 interface shares its interrupt with the other logical | |
4341 | devices on the card, set <constant>MPU401_INFO_IRQ_HOOK</constant> | |
4342 | (see <link linkend="midi-interface-interrupt-handler"><citetitle> | |
4343 | below</citetitle></link>). | |
4344 | </para> | |
4345 | ||
1da177e4 LT |
4346 | <para> |
4347 | Usually, the port address corresponds to the command port and | |
4348 | port + 1 corresponds to the data port. If not, you may change | |
4349 | the <structfield>cport</structfield> field of | |
446ab5f5 TI |
4350 | struct <structname>snd_mpu401</structname> manually |
4351 | afterward. However, <structname>snd_mpu401</structname> pointer is not | |
1da177e4 LT |
4352 | returned explicitly by |
4353 | <function>snd_mpu401_uart_new()</function>. You need to cast | |
4354 | rmidi->private_data to | |
446ab5f5 | 4355 | <structname>snd_mpu401</structname> explicitly, |
1da177e4 LT |
4356 | |
4357 | <informalexample> | |
4358 | <programlisting> | |
4359 | <![CDATA[ | |
446ab5f5 | 4360 | struct snd_mpu401 *mpu; |
1da177e4 LT |
4361 | mpu = rmidi->private_data; |
4362 | ]]> | |
4363 | </programlisting> | |
4364 | </informalexample> | |
4365 | ||
4366 | and reset the cport as you like: | |
4367 | ||
4368 | <informalexample> | |
4369 | <programlisting> | |
4370 | <![CDATA[ | |
4371 | mpu->cport = my_own_control_port; | |
4372 | ]]> | |
4373 | </programlisting> | |
4374 | </informalexample> | |
4375 | </para> | |
4376 | ||
4377 | <para> | |
dba8b469 CL |
4378 | The 6th argument specifies the ISA irq number that will be |
4379 | allocated. If no interrupt is to be allocated (because your | |
4380 | code is already allocating a shared interrupt, or because the | |
4381 | device does not use interrupts), pass -1 instead. | |
4382 | For a MPU-401 device without an interrupt, a polling timer | |
4383 | will be used instead. | |
1da177e4 LT |
4384 | </para> |
4385 | </section> | |
4386 | ||
4387 | <section id="midi-interface-interrupt-handler"> | |
4388 | <title>Interrupt Handler</title> | |
4389 | <para> | |
4390 | When the interrupt is allocated in | |
dba8b469 CL |
4391 | <function>snd_mpu401_uart_new()</function>, an exclusive ISA |
4392 | interrupt handler is automatically used, hence you don't have | |
4393 | anything else to do than creating the mpu401 stuff. Otherwise, you | |
4394 | have to set <constant>MPU401_INFO_IRQ_HOOK</constant>, and call | |
4395 | <function>snd_mpu401_uart_interrupt()</function> explicitly from your | |
4396 | own interrupt handler when it has determined that a UART interrupt | |
4397 | has occurred. | |
1da177e4 LT |
4398 | </para> |
4399 | ||
4400 | <para> | |
4401 | In this case, you need to pass the private_data of the | |
4402 | returned rawmidi object from | |
4403 | <function>snd_mpu401_uart_new()</function> as the second | |
4404 | argument of <function>snd_mpu401_uart_interrupt()</function>. | |
4405 | ||
4406 | <informalexample> | |
4407 | <programlisting> | |
4408 | <![CDATA[ | |
4409 | snd_mpu401_uart_interrupt(irq, rmidi->private_data, regs); | |
4410 | ]]> | |
4411 | </programlisting> | |
4412 | </informalexample> | |
4413 | </para> | |
4414 | </section> | |
4415 | ||
4416 | </chapter> | |
4417 | ||
4418 | ||
4419 | <!-- ****************************************************** --> | |
4420 | <!-- RawMIDI Interface --> | |
4421 | <!-- ****************************************************** --> | |
4422 | <chapter id="rawmidi-interface"> | |
4423 | <title>RawMIDI Interface</title> | |
4424 | ||
4425 | <section id="rawmidi-interface-overview"> | |
4426 | <title>Overview</title> | |
4427 | ||
4428 | <para> | |
4429 | The raw MIDI interface is used for hardware MIDI ports that can | |
4430 | be accessed as a byte stream. It is not used for synthesizer | |
4431 | chips that do not directly understand MIDI. | |
4432 | </para> | |
4433 | ||
4434 | <para> | |
4435 | ALSA handles file and buffer management. All you have to do is | |
4436 | to write some code to move data between the buffer and the | |
4437 | hardware. | |
4438 | </para> | |
4439 | ||
4440 | <para> | |
4441 | The rawmidi API is defined in | |
4442 | <filename><sound/rawmidi.h></filename>. | |
4443 | </para> | |
4444 | </section> | |
4445 | ||
4446 | <section id="rawmidi-interface-constructor"> | |
4447 | <title>Constructor</title> | |
4448 | ||
4449 | <para> | |
4450 | To create a rawmidi device, call the | |
4451 | <function>snd_rawmidi_new</function> function: | |
4452 | <informalexample> | |
4453 | <programlisting> | |
4454 | <![CDATA[ | |
446ab5f5 | 4455 | struct snd_rawmidi *rmidi; |
1da177e4 LT |
4456 | err = snd_rawmidi_new(chip->card, "MyMIDI", 0, outs, ins, &rmidi); |
4457 | if (err < 0) | |
4458 | return err; | |
4459 | rmidi->private_data = chip; | |
4460 | strcpy(rmidi->name, "My MIDI"); | |
4461 | rmidi->info_flags = SNDRV_RAWMIDI_INFO_OUTPUT | | |
4462 | SNDRV_RAWMIDI_INFO_INPUT | | |
4463 | SNDRV_RAWMIDI_INFO_DUPLEX; | |
4464 | ]]> | |
4465 | </programlisting> | |
4466 | </informalexample> | |
4467 | </para> | |
4468 | ||
4469 | <para> | |
4470 | The first argument is the card pointer, the second argument is | |
4471 | the ID string. | |
4472 | </para> | |
4473 | ||
4474 | <para> | |
4475 | The third argument is the index of this component. You can | |
4476 | create up to 8 rawmidi devices. | |
4477 | </para> | |
4478 | ||
4479 | <para> | |
4480 | The fourth and fifth arguments are the number of output and | |
3f03f7c5 MO |
4481 | input substreams, respectively, of this device (a substream is |
4482 | the equivalent of a MIDI port). | |
1da177e4 LT |
4483 | </para> |
4484 | ||
4485 | <para> | |
4486 | Set the <structfield>info_flags</structfield> field to specify | |
4487 | the capabilities of the device. | |
4488 | Set <constant>SNDRV_RAWMIDI_INFO_OUTPUT</constant> if there is | |
4489 | at least one output port, | |
4490 | <constant>SNDRV_RAWMIDI_INFO_INPUT</constant> if there is at | |
4491 | least one input port, | |
4492 | and <constant>SNDRV_RAWMIDI_INFO_DUPLEX</constant> if the device | |
4493 | can handle output and input at the same time. | |
4494 | </para> | |
4495 | ||
4496 | <para> | |
4497 | After the rawmidi device is created, you need to set the | |
4498 | operators (callbacks) for each substream. There are helper | |
3f03f7c5 | 4499 | functions to set the operators for all the substreams of a device: |
1da177e4 LT |
4500 | <informalexample> |
4501 | <programlisting> | |
4502 | <![CDATA[ | |
4503 | snd_rawmidi_set_ops(rmidi, SNDRV_RAWMIDI_STREAM_OUTPUT, &snd_mymidi_output_ops); | |
4504 | snd_rawmidi_set_ops(rmidi, SNDRV_RAWMIDI_STREAM_INPUT, &snd_mymidi_input_ops); | |
4505 | ]]> | |
4506 | </programlisting> | |
4507 | </informalexample> | |
4508 | </para> | |
4509 | ||
4510 | <para> | |
4511 | The operators are usually defined like this: | |
4512 | <informalexample> | |
4513 | <programlisting> | |
4514 | <![CDATA[ | |
446ab5f5 | 4515 | static struct snd_rawmidi_ops snd_mymidi_output_ops = { |
1da177e4 LT |
4516 | .open = snd_mymidi_output_open, |
4517 | .close = snd_mymidi_output_close, | |
4518 | .trigger = snd_mymidi_output_trigger, | |
4519 | }; | |
4520 | ]]> | |
4521 | </programlisting> | |
4522 | </informalexample> | |
4523 | These callbacks are explained in the <link | |
4524 | linkend="rawmidi-interface-callbacks"><citetitle>Callbacks</citetitle></link> | |
4525 | section. | |
4526 | </para> | |
4527 | ||
4528 | <para> | |
3f03f7c5 MO |
4529 | If there are more than one substream, you should give a |
4530 | unique name to each of them: | |
1da177e4 LT |
4531 | <informalexample> |
4532 | <programlisting> | |
4533 | <![CDATA[ | |
446ab5f5 | 4534 | struct snd_rawmidi_substream *substream; |
95a5b085 TI |
4535 | list_for_each_entry(substream, |
4536 | &rmidi->streams[SNDRV_RAWMIDI_STREAM_OUTPUT].substreams, | |
4537 | list { | |
1da177e4 LT |
4538 | sprintf(substream->name, "My MIDI Port %d", substream->number + 1); |
4539 | } | |
4540 | /* same for SNDRV_RAWMIDI_STREAM_INPUT */ | |
4541 | ]]> | |
4542 | </programlisting> | |
4543 | </informalexample> | |
4544 | </para> | |
4545 | </section> | |
4546 | ||
4547 | <section id="rawmidi-interface-callbacks"> | |
4548 | <title>Callbacks</title> | |
4549 | ||
4550 | <para> | |
3f03f7c5 | 4551 | In all the callbacks, the private data that you've set for the |
1da177e4 LT |
4552 | rawmidi device can be accessed as |
4553 | substream->rmidi->private_data. | |
4554 | <!-- <code> isn't available before DocBook 4.3 --> | |
4555 | </para> | |
4556 | ||
4557 | <para> | |
4558 | If there is more than one port, your callbacks can determine the | |
446ab5f5 | 4559 | port index from the struct snd_rawmidi_substream data passed to each |
1da177e4 LT |
4560 | callback: |
4561 | <informalexample> | |
4562 | <programlisting> | |
4563 | <![CDATA[ | |
446ab5f5 | 4564 | struct snd_rawmidi_substream *substream; |
1da177e4 LT |
4565 | int index = substream->number; |
4566 | ]]> | |
4567 | </programlisting> | |
4568 | </informalexample> | |
4569 | </para> | |
4570 | ||
4571 | <section id="rawmidi-interface-op-open"> | |
4572 | <title><function>open</function> callback</title> | |
4573 | ||
4574 | <informalexample> | |
4575 | <programlisting> | |
4576 | <![CDATA[ | |
446ab5f5 | 4577 | static int snd_xxx_open(struct snd_rawmidi_substream *substream); |
1da177e4 LT |
4578 | ]]> |
4579 | </programlisting> | |
4580 | </informalexample> | |
4581 | ||
4582 | <para> | |
4583 | This is called when a substream is opened. | |
3f03f7c5 MO |
4584 | You can initialize the hardware here, but you shouldn't |
4585 | start transmitting/receiving data yet. | |
1da177e4 LT |
4586 | </para> |
4587 | </section> | |
4588 | ||
4589 | <section id="rawmidi-interface-op-close"> | |
4590 | <title><function>close</function> callback</title> | |
4591 | ||
4592 | <informalexample> | |
4593 | <programlisting> | |
4594 | <![CDATA[ | |
446ab5f5 | 4595 | static int snd_xxx_close(struct snd_rawmidi_substream *substream); |
1da177e4 LT |
4596 | ]]> |
4597 | </programlisting> | |
4598 | </informalexample> | |
4599 | ||
4600 | <para> | |
4601 | Guess what. | |
4602 | </para> | |
4603 | ||
4604 | <para> | |
4605 | The <function>open</function> and <function>close</function> | |
4606 | callbacks of a rawmidi device are serialized with a mutex, | |
4607 | and can sleep. | |
4608 | </para> | |
4609 | </section> | |
4610 | ||
4611 | <section id="rawmidi-interface-op-trigger-out"> | |
4612 | <title><function>trigger</function> callback for output | |
4613 | substreams</title> | |
4614 | ||
4615 | <informalexample> | |
4616 | <programlisting> | |
4617 | <![CDATA[ | |
446ab5f5 | 4618 | static void snd_xxx_output_trigger(struct snd_rawmidi_substream *substream, int up); |
1da177e4 LT |
4619 | ]]> |
4620 | </programlisting> | |
4621 | </informalexample> | |
4622 | ||
4623 | <para> | |
4624 | This is called with a nonzero <parameter>up</parameter> | |
4625 | parameter when there is some data in the substream buffer that | |
4626 | must be transmitted. | |
4627 | </para> | |
4628 | ||
4629 | <para> | |
4630 | To read data from the buffer, call | |
4631 | <function>snd_rawmidi_transmit_peek</function>. It will | |
4632 | return the number of bytes that have been read; this will be | |
3f03f7c5 | 4633 | less than the number of bytes requested when there are no more |
1da177e4 | 4634 | data in the buffer. |
3f03f7c5 | 4635 | After the data have been transmitted successfully, call |
1da177e4 LT |
4636 | <function>snd_rawmidi_transmit_ack</function> to remove the |
4637 | data from the substream buffer: | |
4638 | <informalexample> | |
4639 | <programlisting> | |
4640 | <![CDATA[ | |
4641 | unsigned char data; | |
4642 | while (snd_rawmidi_transmit_peek(substream, &data, 1) == 1) { | |
446ab5f5 | 4643 | if (snd_mychip_try_to_transmit(data)) |
1da177e4 LT |
4644 | snd_rawmidi_transmit_ack(substream, 1); |
4645 | else | |
4646 | break; /* hardware FIFO full */ | |
4647 | } | |
4648 | ]]> | |
4649 | </programlisting> | |
4650 | </informalexample> | |
4651 | </para> | |
4652 | ||
4653 | <para> | |
4654 | If you know beforehand that the hardware will accept data, you | |
4655 | can use the <function>snd_rawmidi_transmit</function> function | |
3f03f7c5 | 4656 | which reads some data and removes them from the buffer at once: |
1da177e4 LT |
4657 | <informalexample> |
4658 | <programlisting> | |
4659 | <![CDATA[ | |
446ab5f5 | 4660 | while (snd_mychip_transmit_possible()) { |
1da177e4 LT |
4661 | unsigned char data; |
4662 | if (snd_rawmidi_transmit(substream, &data, 1) != 1) | |
4663 | break; /* no more data */ | |
446ab5f5 | 4664 | snd_mychip_transmit(data); |
1da177e4 LT |
4665 | } |
4666 | ]]> | |
4667 | </programlisting> | |
4668 | </informalexample> | |
4669 | </para> | |
4670 | ||
4671 | <para> | |
4672 | If you know beforehand how many bytes you can accept, you can | |
4673 | use a buffer size greater than one with the | |
4674 | <function>snd_rawmidi_transmit*</function> functions. | |
4675 | </para> | |
4676 | ||
4677 | <para> | |
4678 | The <function>trigger</function> callback must not sleep. If | |
4679 | the hardware FIFO is full before the substream buffer has been | |
4680 | emptied, you have to continue transmitting data later, either | |
4681 | in an interrupt handler, or with a timer if the hardware | |
4682 | doesn't have a MIDI transmit interrupt. | |
4683 | </para> | |
4684 | ||
4685 | <para> | |
4686 | The <function>trigger</function> callback is called with a | |
4687 | zero <parameter>up</parameter> parameter when the transmission | |
4688 | of data should be aborted. | |
4689 | </para> | |
4690 | </section> | |
4691 | ||
4692 | <section id="rawmidi-interface-op-trigger-in"> | |
4693 | <title><function>trigger</function> callback for input | |
4694 | substreams</title> | |
4695 | ||
4696 | <informalexample> | |
4697 | <programlisting> | |
4698 | <![CDATA[ | |
446ab5f5 | 4699 | static void snd_xxx_input_trigger(struct snd_rawmidi_substream *substream, int up); |
1da177e4 LT |
4700 | ]]> |
4701 | </programlisting> | |
4702 | </informalexample> | |
4703 | ||
4704 | <para> | |
4705 | This is called with a nonzero <parameter>up</parameter> | |
4706 | parameter to enable receiving data, or with a zero | |
4707 | <parameter>up</parameter> parameter do disable receiving data. | |
4708 | </para> | |
4709 | ||
4710 | <para> | |
4711 | The <function>trigger</function> callback must not sleep; the | |
4712 | actual reading of data from the device is usually done in an | |
4713 | interrupt handler. | |
4714 | </para> | |
4715 | ||
4716 | <para> | |
4717 | When data reception is enabled, your interrupt handler should | |
4718 | call <function>snd_rawmidi_receive</function> for all received | |
4719 | data: | |
4720 | <informalexample> | |
4721 | <programlisting> | |
4722 | <![CDATA[ | |
4723 | void snd_mychip_midi_interrupt(...) | |
4724 | { | |
4725 | while (mychip_midi_available()) { | |
4726 | unsigned char data; | |
4727 | data = mychip_midi_read(); | |
4728 | snd_rawmidi_receive(substream, &data, 1); | |
4729 | } | |
4730 | } | |
4731 | ]]> | |
4732 | </programlisting> | |
4733 | </informalexample> | |
4734 | </para> | |
4735 | </section> | |
4736 | ||
4737 | <section id="rawmidi-interface-op-drain"> | |
4738 | <title><function>drain</function> callback</title> | |
4739 | ||
4740 | <informalexample> | |
4741 | <programlisting> | |
4742 | <![CDATA[ | |
446ab5f5 | 4743 | static void snd_xxx_drain(struct snd_rawmidi_substream *substream); |
1da177e4 LT |
4744 | ]]> |
4745 | </programlisting> | |
4746 | </informalexample> | |
4747 | ||
4748 | <para> | |
4749 | This is only used with output substreams. This function should wait | |
3f03f7c5 | 4750 | until all data read from the substream buffer have been transmitted. |
1da177e4 LT |
4751 | This ensures that the device can be closed and the driver unloaded |
4752 | without losing data. | |
4753 | </para> | |
4754 | ||
4755 | <para> | |
3f03f7c5 | 4756 | This callback is optional. If you do not set |
446ab5f5 | 4757 | <structfield>drain</structfield> in the struct snd_rawmidi_ops |
1da177e4 LT |
4758 | structure, ALSA will simply wait for 50 milliseconds |
4759 | instead. | |
4760 | </para> | |
4761 | </section> | |
4762 | </section> | |
4763 | ||
4764 | </chapter> | |
4765 | ||
4766 | ||
4767 | <!-- ****************************************************** --> | |
4768 | <!-- Miscellaneous Devices --> | |
4769 | <!-- ****************************************************** --> | |
4770 | <chapter id="misc-devices"> | |
4771 | <title>Miscellaneous Devices</title> | |
4772 | ||
4773 | <section id="misc-devices-opl3"> | |
4774 | <title>FM OPL3</title> | |
4775 | <para> | |
3f03f7c5 | 4776 | The FM OPL3 is still used in many chips (mainly for backward |
1da177e4 LT |
4777 | compatibility). ALSA has a nice OPL3 FM control layer, too. The |
4778 | OPL3 API is defined in | |
4779 | <filename><sound/opl3.h></filename>. | |
4780 | </para> | |
4781 | ||
4782 | <para> | |
3f03f7c5 | 4783 | FM registers can be directly accessed through the direct-FM API, |
1da177e4 LT |
4784 | defined in <filename><sound/asound_fm.h></filename>. In |
4785 | ALSA native mode, FM registers are accessed through | |
25985edc | 4786 | the Hardware-Dependent Device direct-FM extension API, whereas in |
3f03f7c5 MO |
4787 | OSS compatible mode, FM registers can be accessed with the OSS |
4788 | direct-FM compatible API in <filename>/dev/dmfmX</filename> device. | |
1da177e4 LT |
4789 | </para> |
4790 | ||
4791 | <para> | |
3f03f7c5 MO |
4792 | To create the OPL3 component, you have two functions to |
4793 | call. The first one is a constructor for the <type>opl3_t</type> | |
1da177e4 LT |
4794 | instance. |
4795 | ||
4796 | <informalexample> | |
4797 | <programlisting> | |
4798 | <![CDATA[ | |
446ab5f5 | 4799 | struct snd_opl3 *opl3; |
1da177e4 LT |
4800 | snd_opl3_create(card, lport, rport, OPL3_HW_OPL3_XXX, |
4801 | integrated, &opl3); | |
4802 | ]]> | |
4803 | </programlisting> | |
4804 | </informalexample> | |
4805 | </para> | |
4806 | ||
4807 | <para> | |
4808 | The first argument is the card pointer, the second one is the | |
4809 | left port address, and the third is the right port address. In | |
4810 | most cases, the right port is placed at the left port + 2. | |
4811 | </para> | |
4812 | ||
4813 | <para> | |
4814 | The fourth argument is the hardware type. | |
4815 | </para> | |
4816 | ||
4817 | <para> | |
4818 | When the left and right ports have been already allocated by | |
4819 | the card driver, pass non-zero to the fifth argument | |
3f03f7c5 | 4820 | (<parameter>integrated</parameter>). Otherwise, the opl3 module will |
1da177e4 LT |
4821 | allocate the specified ports by itself. |
4822 | </para> | |
4823 | ||
4824 | <para> | |
3f03f7c5 | 4825 | When the accessing the hardware requires special method |
1da177e4 LT |
4826 | instead of the standard I/O access, you can create opl3 instance |
4827 | separately with <function>snd_opl3_new()</function>. | |
4828 | ||
4829 | <informalexample> | |
4830 | <programlisting> | |
4831 | <![CDATA[ | |
446ab5f5 | 4832 | struct snd_opl3 *opl3; |
1da177e4 LT |
4833 | snd_opl3_new(card, OPL3_HW_OPL3_XXX, &opl3); |
4834 | ]]> | |
4835 | </programlisting> | |
4836 | </informalexample> | |
4837 | </para> | |
4838 | ||
4839 | <para> | |
4840 | Then set <structfield>command</structfield>, | |
4841 | <structfield>private_data</structfield> and | |
4842 | <structfield>private_free</structfield> for the private | |
4843 | access function, the private data and the destructor. | |
4844 | The l_port and r_port are not necessarily set. Only the | |
4845 | command must be set properly. You can retrieve the data | |
3f03f7c5 | 4846 | from the opl3->private_data field. |
1da177e4 LT |
4847 | </para> |
4848 | ||
4849 | <para> | |
4850 | After creating the opl3 instance via <function>snd_opl3_new()</function>, | |
4851 | call <function>snd_opl3_init()</function> to initialize the chip to the | |
3f03f7c5 | 4852 | proper state. Note that <function>snd_opl3_create()</function> always |
1da177e4 LT |
4853 | calls it internally. |
4854 | </para> | |
4855 | ||
4856 | <para> | |
4857 | If the opl3 instance is created successfully, then create a | |
4858 | hwdep device for this opl3. | |
4859 | ||
4860 | <informalexample> | |
4861 | <programlisting> | |
4862 | <![CDATA[ | |
446ab5f5 | 4863 | struct snd_hwdep *opl3hwdep; |
1da177e4 LT |
4864 | snd_opl3_hwdep_new(opl3, 0, 1, &opl3hwdep); |
4865 | ]]> | |
4866 | </programlisting> | |
4867 | </informalexample> | |
4868 | </para> | |
4869 | ||
4870 | <para> | |
4871 | The first argument is the <type>opl3_t</type> instance you | |
4872 | created, and the second is the index number, usually 0. | |
4873 | </para> | |
4874 | ||
4875 | <para> | |
4876 | The third argument is the index-offset for the sequencer | |
4877 | client assigned to the OPL3 port. When there is an MPU401-UART, | |
4878 | give 1 for here (UART always takes 0). | |
4879 | </para> | |
4880 | </section> | |
4881 | ||
4882 | <section id="misc-devices-hardware-dependent"> | |
4883 | <title>Hardware-Dependent Devices</title> | |
4884 | <para> | |
3f03f7c5 | 4885 | Some chips need user-space access for special |
1da177e4 LT |
4886 | controls or for loading the micro code. In such a case, you can |
4887 | create a hwdep (hardware-dependent) device. The hwdep API is | |
4888 | defined in <filename><sound/hwdep.h></filename>. You can | |
4889 | find examples in opl3 driver or | |
4890 | <filename>isa/sb/sb16_csp.c</filename>. | |
4891 | </para> | |
4892 | ||
4893 | <para> | |
3f03f7c5 | 4894 | The creation of the <type>hwdep</type> instance is done via |
1da177e4 LT |
4895 | <function>snd_hwdep_new()</function>. |
4896 | ||
4897 | <informalexample> | |
4898 | <programlisting> | |
4899 | <![CDATA[ | |
446ab5f5 | 4900 | struct snd_hwdep *hw; |
1da177e4 LT |
4901 | snd_hwdep_new(card, "My HWDEP", 0, &hw); |
4902 | ]]> | |
4903 | </programlisting> | |
4904 | </informalexample> | |
4905 | ||
4906 | where the third argument is the index number. | |
4907 | </para> | |
4908 | ||
4909 | <para> | |
4910 | You can then pass any pointer value to the | |
4911 | <parameter>private_data</parameter>. | |
4912 | If you assign a private data, you should define the | |
3f03f7c5 MO |
4913 | destructor, too. The destructor function is set in |
4914 | the <structfield>private_free</structfield> field. | |
1da177e4 LT |
4915 | |
4916 | <informalexample> | |
4917 | <programlisting> | |
4918 | <![CDATA[ | |
446ab5f5 | 4919 | struct mydata *p = kmalloc(sizeof(*p), GFP_KERNEL); |
1da177e4 LT |
4920 | hw->private_data = p; |
4921 | hw->private_free = mydata_free; | |
4922 | ]]> | |
4923 | </programlisting> | |
4924 | </informalexample> | |
4925 | ||
3f03f7c5 | 4926 | and the implementation of the destructor would be: |
1da177e4 LT |
4927 | |
4928 | <informalexample> | |
4929 | <programlisting> | |
4930 | <![CDATA[ | |
446ab5f5 | 4931 | static void mydata_free(struct snd_hwdep *hw) |
1da177e4 | 4932 | { |
446ab5f5 | 4933 | struct mydata *p = hw->private_data; |
1da177e4 LT |
4934 | kfree(p); |
4935 | } | |
4936 | ]]> | |
4937 | </programlisting> | |
4938 | </informalexample> | |
4939 | </para> | |
4940 | ||
4941 | <para> | |
4942 | The arbitrary file operations can be defined for this | |
4943 | instance. The file operators are defined in | |
3f03f7c5 | 4944 | the <parameter>ops</parameter> table. For example, assume that |
1da177e4 LT |
4945 | this chip needs an ioctl. |
4946 | ||
4947 | <informalexample> | |
4948 | <programlisting> | |
4949 | <![CDATA[ | |
4950 | hw->ops.open = mydata_open; | |
4951 | hw->ops.ioctl = mydata_ioctl; | |
4952 | hw->ops.release = mydata_release; | |
4953 | ]]> | |
4954 | </programlisting> | |
4955 | </informalexample> | |
4956 | ||
4957 | And implement the callback functions as you like. | |
4958 | </para> | |
4959 | </section> | |
4960 | ||
4961 | <section id="misc-devices-IEC958"> | |
4962 | <title>IEC958 (S/PDIF)</title> | |
4963 | <para> | |
4964 | Usually the controls for IEC958 devices are implemented via | |
3f03f7c5 | 4965 | the control interface. There is a macro to compose a name string for |
1da177e4 LT |
4966 | IEC958 controls, <function>SNDRV_CTL_NAME_IEC958()</function> |
4967 | defined in <filename><include/asound.h></filename>. | |
4968 | </para> | |
4969 | ||
4970 | <para> | |
4971 | There are some standard controls for IEC958 status bits. These | |
4972 | controls use the type <type>SNDRV_CTL_ELEM_TYPE_IEC958</type>, | |
4973 | and the size of element is fixed as 4 bytes array | |
3f03f7c5 | 4974 | (value.iec958.status[x]). For the <structfield>info</structfield> |
1da177e4 LT |
4975 | callback, you don't specify |
4976 | the value field for this type (the count field must be set, | |
4977 | though). | |
4978 | </para> | |
4979 | ||
4980 | <para> | |
4981 | <quote>IEC958 Playback Con Mask</quote> is used to return the | |
4982 | bit-mask for the IEC958 status bits of consumer mode. Similarly, | |
4983 | <quote>IEC958 Playback Pro Mask</quote> returns the bitmask for | |
4984 | professional mode. They are read-only controls, and are defined | |
4985 | as MIXER controls (iface = | |
4986 | <constant>SNDRV_CTL_ELEM_IFACE_MIXER</constant>). | |
4987 | </para> | |
4988 | ||
4989 | <para> | |
4990 | Meanwhile, <quote>IEC958 Playback Default</quote> control is | |
4991 | defined for getting and setting the current default IEC958 | |
4992 | bits. Note that this one is usually defined as a PCM control | |
4993 | (iface = <constant>SNDRV_CTL_ELEM_IFACE_PCM</constant>), | |
4994 | although in some places it's defined as a MIXER control. | |
4995 | </para> | |
4996 | ||
4997 | <para> | |
4998 | In addition, you can define the control switches to | |
4999 | enable/disable or to set the raw bit mode. The implementation | |
5000 | will depend on the chip, but the control should be named as | |
5001 | <quote>IEC958 xxx</quote>, preferably using | |
3f03f7c5 | 5002 | the <function>SNDRV_CTL_NAME_IEC958()</function> macro. |
1da177e4 LT |
5003 | </para> |
5004 | ||
5005 | <para> | |
5006 | You can find several cases, for example, | |
5007 | <filename>pci/emu10k1</filename>, | |
5008 | <filename>pci/ice1712</filename>, or | |
5009 | <filename>pci/cmipci.c</filename>. | |
5010 | </para> | |
5011 | </section> | |
5012 | ||
5013 | </chapter> | |
5014 | ||
5015 | ||
5016 | <!-- ****************************************************** --> | |
5017 | <!-- Buffer and Memory Management --> | |
5018 | <!-- ****************************************************** --> | |
5019 | <chapter id="buffer-and-memory"> | |
5020 | <title>Buffer and Memory Management</title> | |
5021 | ||
5022 | <section id="buffer-and-memory-buffer-types"> | |
5023 | <title>Buffer Types</title> | |
5024 | <para> | |
5025 | ALSA provides several different buffer allocation functions | |
5026 | depending on the bus and the architecture. All these have a | |
5027 | consistent API. The allocation of physically-contiguous pages is | |
5028 | done via | |
5029 | <function>snd_malloc_xxx_pages()</function> function, where xxx | |
5030 | is the bus type. | |
5031 | </para> | |
5032 | ||
5033 | <para> | |
5034 | The allocation of pages with fallback is | |
5035 | <function>snd_malloc_xxx_pages_fallback()</function>. This | |
5036 | function tries to allocate the specified pages but if the pages | |
3f03f7c5 | 5037 | are not available, it tries to reduce the page sizes until |
1da177e4 LT |
5038 | enough space is found. |
5039 | </para> | |
5040 | ||
5041 | <para> | |
3f03f7c5 | 5042 | The release the pages, call |
1da177e4 LT |
5043 | <function>snd_free_xxx_pages()</function> function. |
5044 | </para> | |
5045 | ||
5046 | <para> | |
5047 | Usually, ALSA drivers try to allocate and reserve | |
5048 | a large contiguous physical space | |
5049 | at the time the module is loaded for the later use. | |
5050 | This is called <quote>pre-allocation</quote>. | |
3f03f7c5 MO |
5051 | As already written, you can call the following function at |
5052 | pcm instance construction time (in the case of PCI bus). | |
1da177e4 LT |
5053 | |
5054 | <informalexample> | |
5055 | <programlisting> | |
5056 | <![CDATA[ | |
5057 | snd_pcm_lib_preallocate_pages_for_all(pcm, SNDRV_DMA_TYPE_DEV, | |
5058 | snd_dma_pci_data(pci), size, max); | |
5059 | ]]> | |
5060 | </programlisting> | |
5061 | </informalexample> | |
5062 | ||
5063 | where <parameter>size</parameter> is the byte size to be | |
3f03f7c5 MO |
5064 | pre-allocated and the <parameter>max</parameter> is the maximum |
5065 | size to be changed via the <filename>prealloc</filename> proc file. | |
5066 | The allocator will try to get an area as large as possible | |
1da177e4 LT |
5067 | within the given size. |
5068 | </para> | |
5069 | ||
5070 | <para> | |
5071 | The second argument (type) and the third argument (device pointer) | |
5072 | are dependent on the bus. | |
3f03f7c5 | 5073 | In the case of the ISA bus, pass <function>snd_dma_isa_data()</function> |
1da177e4 LT |
5074 | as the third argument with <constant>SNDRV_DMA_TYPE_DEV</constant> type. |
5075 | For the continuous buffer unrelated to the bus can be pre-allocated | |
5076 | with <constant>SNDRV_DMA_TYPE_CONTINUOUS</constant> type and the | |
5077 | <function>snd_dma_continuous_data(GFP_KERNEL)</function> device pointer, | |
3f03f7c5 | 5078 | where <constant>GFP_KERNEL</constant> is the kernel allocation flag to |
759ee81b | 5079 | use. |
1da177e4 LT |
5080 | For the PCI scatter-gather buffers, use |
5081 | <constant>SNDRV_DMA_TYPE_DEV_SG</constant> with | |
5082 | <function>snd_dma_pci_data(pci)</function> | |
3f03f7c5 | 5083 | (see the |
1da177e4 | 5084 | <link linkend="buffer-and-memory-non-contiguous"><citetitle>Non-Contiguous Buffers |
3f03f7c5 | 5085 | </citetitle></link> section). |
1da177e4 LT |
5086 | </para> |
5087 | ||
5088 | <para> | |
3f03f7c5 MO |
5089 | Once the buffer is pre-allocated, you can use the |
5090 | allocator in the <structfield>hw_params</structfield> callback: | |
1da177e4 LT |
5091 | |
5092 | <informalexample> | |
5093 | <programlisting> | |
5094 | <![CDATA[ | |
5095 | snd_pcm_lib_malloc_pages(substream, size); | |
5096 | ]]> | |
5097 | </programlisting> | |
5098 | </informalexample> | |
5099 | ||
5100 | Note that you have to pre-allocate to use this function. | |
5101 | </para> | |
5102 | </section> | |
5103 | ||
5104 | <section id="buffer-and-memory-external-hardware"> | |
5105 | <title>External Hardware Buffers</title> | |
5106 | <para> | |
5107 | Some chips have their own hardware buffers and the DMA | |
5108 | transfer from the host memory is not available. In such a case, | |
5109 | you need to either 1) copy/set the audio data directly to the | |
5110 | external hardware buffer, or 2) make an intermediate buffer and | |
5111 | copy/set the data from it to the external hardware buffer in | |
5112 | interrupts (or in tasklets, preferably). | |
5113 | </para> | |
5114 | ||
5115 | <para> | |
3f03f7c5 MO |
5116 | The first case works fine if the external hardware buffer is large |
5117 | enough. This method doesn't need any extra buffers and thus is | |
1da177e4 LT |
5118 | more effective. You need to define the |
5119 | <structfield>copy</structfield> and | |
5120 | <structfield>silence</structfield> callbacks for | |
5121 | the data transfer. However, there is a drawback: it cannot | |
5122 | be mmapped. The examples are GUS's GF1 PCM or emu8000's | |
5123 | wavetable PCM. | |
5124 | </para> | |
5125 | ||
5126 | <para> | |
3f03f7c5 MO |
5127 | The second case allows for mmap on the buffer, although you have |
5128 | to handle an interrupt or a tasklet to transfer the data | |
1da177e4 | 5129 | from the intermediate buffer to the hardware buffer. You can find an |
3f03f7c5 | 5130 | example in the vxpocket driver. |
1da177e4 LT |
5131 | </para> |
5132 | ||
5133 | <para> | |
3f03f7c5 | 5134 | Another case is when the chip uses a PCI memory-map |
1da177e4 | 5135 | region for the buffer instead of the host memory. In this case, |
3f03f7c5 MO |
5136 | mmap is available only on certain architectures like the Intel one. |
5137 | In non-mmap mode, the data cannot be transferred as in the normal | |
5138 | way. Thus you need to define the <structfield>copy</structfield> and | |
5139 | <structfield>silence</structfield> callbacks as well, | |
1da177e4 LT |
5140 | as in the cases above. The examples are found in |
5141 | <filename>rme32.c</filename> and <filename>rme96.c</filename>. | |
5142 | </para> | |
5143 | ||
5144 | <para> | |
3f03f7c5 | 5145 | The implementation of the <structfield>copy</structfield> and |
1da177e4 LT |
5146 | <structfield>silence</structfield> callbacks depends upon |
5147 | whether the hardware supports interleaved or non-interleaved | |
5148 | samples. The <structfield>copy</structfield> callback is | |
5149 | defined like below, a bit | |
5150 | differently depending whether the direction is playback or | |
5151 | capture: | |
5152 | ||
5153 | <informalexample> | |
5154 | <programlisting> | |
5155 | <![CDATA[ | |
446ab5f5 | 5156 | static int playback_copy(struct snd_pcm_substream *substream, int channel, |
1da177e4 | 5157 | snd_pcm_uframes_t pos, void *src, snd_pcm_uframes_t count); |
446ab5f5 | 5158 | static int capture_copy(struct snd_pcm_substream *substream, int channel, |
1da177e4 LT |
5159 | snd_pcm_uframes_t pos, void *dst, snd_pcm_uframes_t count); |
5160 | ]]> | |
5161 | </programlisting> | |
5162 | </informalexample> | |
5163 | </para> | |
5164 | ||
5165 | <para> | |
5166 | In the case of interleaved samples, the second argument | |
5167 | (<parameter>channel</parameter>) is not used. The third argument | |
5168 | (<parameter>pos</parameter>) points the | |
5169 | current position offset in frames. | |
5170 | </para> | |
5171 | ||
5172 | <para> | |
5173 | The meaning of the fourth argument is different between | |
5174 | playback and capture. For playback, it holds the source data | |
5175 | pointer, and for capture, it's the destination data pointer. | |
5176 | </para> | |
5177 | ||
5178 | <para> | |
5179 | The last argument is the number of frames to be copied. | |
5180 | </para> | |
5181 | ||
5182 | <para> | |
5183 | What you have to do in this callback is again different | |
3f03f7c5 MO |
5184 | between playback and capture directions. In the |
5185 | playback case, you copy the given amount of data | |
1da177e4 LT |
5186 | (<parameter>count</parameter>) at the specified pointer |
5187 | (<parameter>src</parameter>) to the specified offset | |
5188 | (<parameter>pos</parameter>) on the hardware buffer. When | |
5189 | coded like memcpy-like way, the copy would be like: | |
5190 | ||
5191 | <informalexample> | |
5192 | <programlisting> | |
5193 | <![CDATA[ | |
5194 | my_memcpy(my_buffer + frames_to_bytes(runtime, pos), src, | |
5195 | frames_to_bytes(runtime, count)); | |
5196 | ]]> | |
5197 | </programlisting> | |
5198 | </informalexample> | |
5199 | </para> | |
5200 | ||
5201 | <para> | |
3f03f7c5 | 5202 | For the capture direction, you copy the given amount of |
1da177e4 LT |
5203 | data (<parameter>count</parameter>) at the specified offset |
5204 | (<parameter>pos</parameter>) on the hardware buffer to the | |
5205 | specified pointer (<parameter>dst</parameter>). | |
5206 | ||
5207 | <informalexample> | |
5208 | <programlisting> | |
5209 | <![CDATA[ | |
5210 | my_memcpy(dst, my_buffer + frames_to_bytes(runtime, pos), | |
5211 | frames_to_bytes(runtime, count)); | |
5212 | ]]> | |
5213 | </programlisting> | |
5214 | </informalexample> | |
5215 | ||
3f03f7c5 | 5216 | Note that both the position and the amount of data are given |
1da177e4 LT |
5217 | in frames. |
5218 | </para> | |
5219 | ||
5220 | <para> | |
5221 | In the case of non-interleaved samples, the implementation | |
5222 | will be a bit more complicated. | |
5223 | </para> | |
5224 | ||
5225 | <para> | |
5226 | You need to check the channel argument, and if it's -1, copy | |
5227 | the whole channels. Otherwise, you have to copy only the | |
5228 | specified channel. Please check | |
5229 | <filename>isa/gus/gus_pcm.c</filename> as an example. | |
5230 | </para> | |
5231 | ||
5232 | <para> | |
5233 | The <structfield>silence</structfield> callback is also | |
5234 | implemented in a similar way. | |
5235 | ||
5236 | <informalexample> | |
5237 | <programlisting> | |
5238 | <![CDATA[ | |
446ab5f5 | 5239 | static int silence(struct snd_pcm_substream *substream, int channel, |
1da177e4 LT |
5240 | snd_pcm_uframes_t pos, snd_pcm_uframes_t count); |
5241 | ]]> | |
5242 | </programlisting> | |
5243 | </informalexample> | |
5244 | </para> | |
5245 | ||
5246 | <para> | |
3f03f7c5 | 5247 | The meanings of arguments are the same as in the |
1da177e4 LT |
5248 | <structfield>copy</structfield> |
5249 | callback, although there is no <parameter>src/dst</parameter> | |
5250 | argument. In the case of interleaved samples, the channel | |
5251 | argument has no meaning, as well as on | |
5252 | <structfield>copy</structfield> callback. | |
5253 | </para> | |
5254 | ||
5255 | <para> | |
5256 | The role of <structfield>silence</structfield> callback is to | |
5257 | set the given amount | |
5258 | (<parameter>count</parameter>) of silence data at the | |
5259 | specified offset (<parameter>pos</parameter>) on the hardware | |
5260 | buffer. Suppose that the data format is signed (that is, the | |
5261 | silent-data is 0), and the implementation using a memset-like | |
5262 | function would be like: | |
5263 | ||
5264 | <informalexample> | |
5265 | <programlisting> | |
5266 | <![CDATA[ | |
5267 | my_memcpy(my_buffer + frames_to_bytes(runtime, pos), 0, | |
5268 | frames_to_bytes(runtime, count)); | |
5269 | ]]> | |
5270 | </programlisting> | |
5271 | </informalexample> | |
5272 | </para> | |
5273 | ||
5274 | <para> | |
5275 | In the case of non-interleaved samples, again, the | |
5276 | implementation becomes a bit more complicated. See, for example, | |
5277 | <filename>isa/gus/gus_pcm.c</filename>. | |
5278 | </para> | |
5279 | </section> | |
5280 | ||
5281 | <section id="buffer-and-memory-non-contiguous"> | |
5282 | <title>Non-Contiguous Buffers</title> | |
5283 | <para> | |
3f03f7c5 MO |
5284 | If your hardware supports the page table as in emu10k1 or the |
5285 | buffer descriptors as in via82xx, you can use the scatter-gather | |
1da177e4 LT |
5286 | (SG) DMA. ALSA provides an interface for handling SG-buffers. |
5287 | The API is provided in <filename><sound/pcm.h></filename>. | |
5288 | </para> | |
5289 | ||
5290 | <para> | |
5291 | For creating the SG-buffer handler, call | |
5292 | <function>snd_pcm_lib_preallocate_pages()</function> or | |
5293 | <function>snd_pcm_lib_preallocate_pages_for_all()</function> | |
5294 | with <constant>SNDRV_DMA_TYPE_DEV_SG</constant> | |
5295 | in the PCM constructor like other PCI pre-allocator. | |
3f03f7c5 | 5296 | You need to pass <function>snd_dma_pci_data(pci)</function>, |
1da177e4 LT |
5297 | where pci is the struct <structname>pci_dev</structname> pointer |
5298 | of the chip as well. | |
44275f18 | 5299 | The <type>struct snd_sg_buf</type> instance is created as |
1da177e4 LT |
5300 | substream->dma_private. You can cast |
5301 | the pointer like: | |
5302 | ||
5303 | <informalexample> | |
5304 | <programlisting> | |
5305 | <![CDATA[ | |
44275f18 | 5306 | struct snd_sg_buf *sgbuf = (struct snd_sg_buf *)substream->dma_private; |
1da177e4 LT |
5307 | ]]> |
5308 | </programlisting> | |
5309 | </informalexample> | |
5310 | </para> | |
5311 | ||
5312 | <para> | |
5313 | Then call <function>snd_pcm_lib_malloc_pages()</function> | |
3f03f7c5 | 5314 | in the <structfield>hw_params</structfield> callback |
1da177e4 LT |
5315 | as well as in the case of normal PCI buffer. |
5316 | The SG-buffer handler will allocate the non-contiguous kernel | |
5317 | pages of the given size and map them onto the virtually contiguous | |
5318 | memory. The virtual pointer is addressed in runtime->dma_area. | |
5319 | The physical address (runtime->dma_addr) is set to zero, | |
af901ca1 | 5320 | because the buffer is physically non-contiguous. |
1da177e4 LT |
5321 | The physical address table is set up in sgbuf->table. |
5322 | You can get the physical address at a certain offset via | |
5323 | <function>snd_pcm_sgbuf_get_addr()</function>. | |
5324 | </para> | |
5325 | ||
5326 | <para> | |
5327 | When a SG-handler is used, you need to set | |
5328 | <function>snd_pcm_sgbuf_ops_page</function> as | |
5329 | the <structfield>page</structfield> callback. | |
5330 | (See <link linkend="pcm-interface-operators-page-callback"> | |
5331 | <citetitle>page callback section</citetitle></link>.) | |
5332 | </para> | |
5333 | ||
5334 | <para> | |
3f03f7c5 | 5335 | To release the data, call |
1da177e4 LT |
5336 | <function>snd_pcm_lib_free_pages()</function> in the |
5337 | <structfield>hw_free</structfield> callback as usual. | |
5338 | </para> | |
5339 | </section> | |
5340 | ||
5341 | <section id="buffer-and-memory-vmalloced"> | |
5342 | <title>Vmalloc'ed Buffers</title> | |
5343 | <para> | |
5344 | It's possible to use a buffer allocated via | |
5345 | <function>vmalloc</function>, for example, for an intermediate | |
5346 | buffer. Since the allocated pages are not contiguous, you need | |
5347 | to set the <structfield>page</structfield> callback to obtain | |
5348 | the physical address at every offset. | |
5349 | </para> | |
5350 | ||
5351 | <para> | |
5352 | The implementation of <structfield>page</structfield> callback | |
5353 | would be like this: | |
5354 | ||
5355 | <informalexample> | |
5356 | <programlisting> | |
5357 | <![CDATA[ | |
5358 | #include <linux/vmalloc.h> | |
5359 | ||
5360 | /* get the physical page pointer on the given offset */ | |
446ab5f5 | 5361 | static struct page *mychip_page(struct snd_pcm_substream *substream, |
1da177e4 LT |
5362 | unsigned long offset) |
5363 | { | |
5364 | void *pageptr = substream->runtime->dma_area + offset; | |
5365 | return vmalloc_to_page(pageptr); | |
5366 | } | |
5367 | ]]> | |
5368 | </programlisting> | |
5369 | </informalexample> | |
5370 | </para> | |
5371 | </section> | |
5372 | ||
5373 | </chapter> | |
5374 | ||
5375 | ||
5376 | <!-- ****************************************************** --> | |
5377 | <!-- Proc Interface --> | |
5378 | <!-- ****************************************************** --> | |
5379 | <chapter id="proc-interface"> | |
5380 | <title>Proc Interface</title> | |
5381 | <para> | |
5382 | ALSA provides an easy interface for procfs. The proc files are | |
5383 | very useful for debugging. I recommend you set up proc files if | |
5384 | you write a driver and want to get a running status or register | |
5385 | dumps. The API is found in | |
5386 | <filename><sound/info.h></filename>. | |
5387 | </para> | |
5388 | ||
5389 | <para> | |
3f03f7c5 | 5390 | To create a proc file, call |
1da177e4 LT |
5391 | <function>snd_card_proc_new()</function>. |
5392 | ||
5393 | <informalexample> | |
5394 | <programlisting> | |
5395 | <![CDATA[ | |
446ab5f5 | 5396 | struct snd_info_entry *entry; |
1da177e4 LT |
5397 | int err = snd_card_proc_new(card, "my-file", &entry); |
5398 | ]]> | |
5399 | </programlisting> | |
5400 | </informalexample> | |
5401 | ||
3f03f7c5 | 5402 | where the second argument specifies the name of the proc file to be |
1da177e4 LT |
5403 | created. The above example will create a file |
5404 | <filename>my-file</filename> under the card directory, | |
5405 | e.g. <filename>/proc/asound/card0/my-file</filename>. | |
5406 | </para> | |
5407 | ||
5408 | <para> | |
5409 | Like other components, the proc entry created via | |
5410 | <function>snd_card_proc_new()</function> will be registered and | |
5411 | released automatically in the card registration and release | |
5412 | functions. | |
5413 | </para> | |
5414 | ||
5415 | <para> | |
5416 | When the creation is successful, the function stores a new | |
3f03f7c5 MO |
5417 | instance in the pointer given in the third argument. |
5418 | It is initialized as a text proc file for read only. To use | |
1da177e4 LT |
5419 | this proc file as a read-only text file as it is, set the read |
5420 | callback with a private data via | |
5421 | <function>snd_info_set_text_ops()</function>. | |
5422 | ||
5423 | <informalexample> | |
5424 | <programlisting> | |
5425 | <![CDATA[ | |
bf850204 | 5426 | snd_info_set_text_ops(entry, chip, my_proc_read); |
1da177e4 LT |
5427 | ]]> |
5428 | </programlisting> | |
5429 | </informalexample> | |
5430 | ||
5431 | where the second argument (<parameter>chip</parameter>) is the | |
5432 | private data to be used in the callbacks. The third parameter | |
5433 | specifies the read buffer size and the fourth | |
5434 | (<parameter>my_proc_read</parameter>) is the callback function, which | |
5435 | is defined like | |
5436 | ||
5437 | <informalexample> | |
5438 | <programlisting> | |
5439 | <![CDATA[ | |
446ab5f5 TI |
5440 | static void my_proc_read(struct snd_info_entry *entry, |
5441 | struct snd_info_buffer *buffer); | |
1da177e4 LT |
5442 | ]]> |
5443 | </programlisting> | |
5444 | </informalexample> | |
5445 | ||
5446 | </para> | |
5447 | ||
5448 | <para> | |
5449 | In the read callback, use <function>snd_iprintf()</function> for | |
5450 | output strings, which works just like normal | |
5451 | <function>printf()</function>. For example, | |
5452 | ||
5453 | <informalexample> | |
5454 | <programlisting> | |
5455 | <![CDATA[ | |
446ab5f5 TI |
5456 | static void my_proc_read(struct snd_info_entry *entry, |
5457 | struct snd_info_buffer *buffer) | |
1da177e4 | 5458 | { |
446ab5f5 | 5459 | struct my_chip *chip = entry->private_data; |
1da177e4 LT |
5460 | |
5461 | snd_iprintf(buffer, "This is my chip!\n"); | |
5462 | snd_iprintf(buffer, "Port = %ld\n", chip->port); | |
5463 | } | |
5464 | ]]> | |
5465 | </programlisting> | |
5466 | </informalexample> | |
5467 | </para> | |
5468 | ||
5469 | <para> | |
3f03f7c5 MO |
5470 | The file permissions can be changed afterwards. As default, it's |
5471 | set as read only for all users. If you want to add write | |
5472 | permission for the user (root as default), do as follows: | |
1da177e4 LT |
5473 | |
5474 | <informalexample> | |
5475 | <programlisting> | |
5476 | <![CDATA[ | |
5477 | entry->mode = S_IFREG | S_IRUGO | S_IWUSR; | |
5478 | ]]> | |
5479 | </programlisting> | |
5480 | </informalexample> | |
5481 | ||
5482 | and set the write buffer size and the callback | |
5483 | ||
5484 | <informalexample> | |
5485 | <programlisting> | |
5486 | <![CDATA[ | |
1da177e4 LT |
5487 | entry->c.text.write = my_proc_write; |
5488 | ]]> | |
5489 | </programlisting> | |
5490 | </informalexample> | |
5491 | </para> | |
5492 | ||
1da177e4 LT |
5493 | <para> |
5494 | For the write callback, you can use | |
5495 | <function>snd_info_get_line()</function> to get a text line, and | |
5496 | <function>snd_info_get_str()</function> to retrieve a string from | |
5497 | the line. Some examples are found in | |
5498 | <filename>core/oss/mixer_oss.c</filename>, core/oss/and | |
5499 | <filename>pcm_oss.c</filename>. | |
5500 | </para> | |
5501 | ||
5502 | <para> | |
3f03f7c5 | 5503 | For a raw-data proc-file, set the attributes as follows: |
1da177e4 LT |
5504 | |
5505 | <informalexample> | |
5506 | <programlisting> | |
5507 | <![CDATA[ | |
5508 | static struct snd_info_entry_ops my_file_io_ops = { | |
5509 | .read = my_file_io_read, | |
5510 | }; | |
5511 | ||
5512 | entry->content = SNDRV_INFO_CONTENT_DATA; | |
5513 | entry->private_data = chip; | |
5514 | entry->c.ops = &my_file_io_ops; | |
5515 | entry->size = 4096; | |
5516 | entry->mode = S_IFREG | S_IRUGO; | |
5517 | ]]> | |
5518 | </programlisting> | |
5519 | </informalexample> | |
c56a3b18 TI |
5520 | |
5521 | For the raw data, <structfield>size</structfield> field must be | |
5522 | set properly. This specifies the maximum size of the proc file access. | |
1da177e4 LT |
5523 | </para> |
5524 | ||
5525 | <para> | |
c56a3b18 TI |
5526 | The read/write callbacks of raw mode are more direct than the text mode. |
5527 | You need to use a low-level I/O functions such as | |
1da177e4 LT |
5528 | <function>copy_from/to_user()</function> to transfer the |
5529 | data. | |
5530 | ||
5531 | <informalexample> | |
5532 | <programlisting> | |
5533 | <![CDATA[ | |
c56a3b18 | 5534 | static ssize_t my_file_io_read(struct snd_info_entry *entry, |
1da177e4 LT |
5535 | void *file_private_data, |
5536 | struct file *file, | |
5537 | char *buf, | |
c56a3b18 TI |
5538 | size_t count, |
5539 | loff_t pos) | |
1da177e4 | 5540 | { |
c56a3b18 | 5541 | if (copy_to_user(buf, local_data + pos, count)) |
1da177e4 | 5542 | return -EFAULT; |
c56a3b18 | 5543 | return count; |
1da177e4 LT |
5544 | } |
5545 | ]]> | |
5546 | </programlisting> | |
5547 | </informalexample> | |
c56a3b18 TI |
5548 | |
5549 | If the size of the info entry has been set up properly, | |
5550 | <structfield>count</structfield> and <structfield>pos</structfield> are | |
5551 | guaranteed to fit within 0 and the given size. | |
5552 | You don't have to check the range in the callbacks unless any | |
5553 | other condition is required. | |
5554 | ||
1da177e4 LT |
5555 | </para> |
5556 | ||
5557 | </chapter> | |
5558 | ||
5559 | ||
5560 | <!-- ****************************************************** --> | |
5561 | <!-- Power Management --> | |
5562 | <!-- ****************************************************** --> | |
5563 | <chapter id="power-management"> | |
5564 | <title>Power Management</title> | |
5565 | <para> | |
670e9f34 | 5566 | If the chip is supposed to work with suspend/resume |
3f03f7c5 MO |
5567 | functions, you need to add power-management code to the |
5568 | driver. The additional code for power-management should be | |
1da177e4 LT |
5569 | <function>ifdef</function>'ed with |
5570 | <constant>CONFIG_PM</constant>. | |
5571 | </para> | |
5572 | ||
5fe76e4d | 5573 | <para> |
3f03f7c5 MO |
5574 | If the driver <emphasis>fully</emphasis> supports suspend/resume |
5575 | that is, the device can be | |
5576 | properly resumed to its state when suspend was called, | |
5577 | you can set the <constant>SNDRV_PCM_INFO_RESUME</constant> flag | |
5578 | in the pcm info field. Usually, this is possible when the | |
5579 | registers of the chip can be safely saved and restored to | |
5580 | RAM. If this is set, the trigger callback is called with | |
5581 | <constant>SNDRV_PCM_TRIGGER_RESUME</constant> after the resume | |
5582 | callback completes. | |
5fe76e4d TI |
5583 | </para> |
5584 | ||
5585 | <para> | |
3f03f7c5 MO |
5586 | Even if the driver doesn't support PM fully but |
5587 | partial suspend/resume is still possible, it's still worthy to | |
5588 | implement suspend/resume callbacks. In such a case, applications | |
5fe76e4d TI |
5589 | would reset the status by calling |
5590 | <function>snd_pcm_prepare()</function> and restart the stream | |
5591 | appropriately. Hence, you can define suspend/resume callbacks | |
5592 | below but don't set <constant>SNDRV_PCM_INFO_RESUME</constant> | |
5593 | info flag to the PCM. | |
5594 | </para> | |
5595 | ||
5596 | <para> | |
3f03f7c5 | 5597 | Note that the trigger with SUSPEND can always be called when |
5fe76e4d | 5598 | <function>snd_pcm_suspend_all</function> is called, |
3f03f7c5 | 5599 | regardless of the <constant>SNDRV_PCM_INFO_RESUME</constant> flag. |
5fe76e4d TI |
5600 | The <constant>RESUME</constant> flag affects only the behavior |
5601 | of <function>snd_pcm_resume()</function>. | |
5602 | (Thus, in theory, | |
5603 | <constant>SNDRV_PCM_TRIGGER_RESUME</constant> isn't needed | |
5604 | to be handled in the trigger callback when no | |
5605 | <constant>SNDRV_PCM_INFO_RESUME</constant> flag is set. But, | |
3f03f7c5 | 5606 | it's better to keep it for compatibility reasons.) |
5fe76e4d | 5607 | </para> |
1da177e4 | 5608 | <para> |
5fe76e4d TI |
5609 | In the earlier version of ALSA drivers, a common |
5610 | power-management layer was provided, but it has been removed. | |
5611 | The driver needs to define the suspend/resume hooks according to | |
3f03f7c5 | 5612 | the bus the device is connected to. In the case of PCI drivers, the |
5fe76e4d | 5613 | callbacks look like below: |
1da177e4 LT |
5614 | |
5615 | <informalexample> | |
5616 | <programlisting> | |
5617 | <![CDATA[ | |
5618 | #ifdef CONFIG_PM | |
5fe76e4d | 5619 | static int snd_my_suspend(struct pci_dev *pci, pm_message_t state) |
1da177e4 | 5620 | { |
5bda9fa1 | 5621 | .... /* do things for suspend */ |
1da177e4 LT |
5622 | return 0; |
5623 | } | |
5fe76e4d | 5624 | static int snd_my_resume(struct pci_dev *pci) |
1da177e4 | 5625 | { |
5bda9fa1 | 5626 | .... /* do things for suspend */ |
1da177e4 LT |
5627 | return 0; |
5628 | } | |
5629 | #endif | |
5630 | ]]> | |
5631 | </programlisting> | |
5632 | </informalexample> | |
5633 | </para> | |
5634 | ||
5635 | <para> | |
3f03f7c5 | 5636 | The scheme of the real suspend job is as follows. |
1da177e4 LT |
5637 | |
5638 | <orderedlist> | |
5fe76e4d TI |
5639 | <listitem><para>Retrieve the card and the chip data.</para></listitem> |
5640 | <listitem><para>Call <function>snd_power_change_state()</function> with | |
5641 | <constant>SNDRV_CTL_POWER_D3hot</constant> to change the | |
5642 | power status.</para></listitem> | |
1da177e4 | 5643 | <listitem><para>Call <function>snd_pcm_suspend_all()</function> to suspend the running PCM streams.</para></listitem> |
5fe76e4d | 5644 | <listitem><para>If AC97 codecs are used, call |
a7306336 | 5645 | <function>snd_ac97_suspend()</function> for each codec.</para></listitem> |
1da177e4 LT |
5646 | <listitem><para>Save the register values if necessary.</para></listitem> |
5647 | <listitem><para>Stop the hardware if necessary.</para></listitem> | |
5fe76e4d TI |
5648 | <listitem><para>Disable the PCI device by calling |
5649 | <function>pci_disable_device()</function>. Then, call | |
5650 | <function>pci_save_state()</function> at last.</para></listitem> | |
1da177e4 LT |
5651 | </orderedlist> |
5652 | </para> | |
5653 | ||
5654 | <para> | |
5655 | A typical code would be like: | |
5656 | ||
5657 | <informalexample> | |
5658 | <programlisting> | |
5659 | <![CDATA[ | |
32357988 | 5660 | static int mychip_suspend(struct pci_dev *pci, pm_message_t state) |
1da177e4 LT |
5661 | { |
5662 | /* (1) */ | |
5fe76e4d TI |
5663 | struct snd_card *card = pci_get_drvdata(pci); |
5664 | struct mychip *chip = card->private_data; | |
1da177e4 | 5665 | /* (2) */ |
5fe76e4d | 5666 | snd_power_change_state(card, SNDRV_CTL_POWER_D3hot); |
1da177e4 | 5667 | /* (3) */ |
5fe76e4d | 5668 | snd_pcm_suspend_all(chip->pcm); |
1da177e4 | 5669 | /* (4) */ |
5fe76e4d | 5670 | snd_ac97_suspend(chip->ac97); |
1da177e4 | 5671 | /* (5) */ |
5fe76e4d TI |
5672 | snd_mychip_save_registers(chip); |
5673 | /* (6) */ | |
5674 | snd_mychip_stop_hardware(chip); | |
5675 | /* (7) */ | |
5676 | pci_disable_device(pci); | |
5677 | pci_save_state(pci); | |
1da177e4 LT |
5678 | return 0; |
5679 | } | |
5680 | ]]> | |
5681 | </programlisting> | |
5682 | </informalexample> | |
5683 | </para> | |
5684 | ||
5685 | <para> | |
3f03f7c5 | 5686 | The scheme of the real resume job is as follows. |
1da177e4 LT |
5687 | |
5688 | <orderedlist> | |
5fe76e4d | 5689 | <listitem><para>Retrieve the card and the chip data.</para></listitem> |
3f03f7c5 | 5690 | <listitem><para>Set up PCI. First, call <function>pci_restore_state()</function>. |
5fe76e4d TI |
5691 | Then enable the pci device again by calling <function>pci_enable_device()</function>. |
5692 | Call <function>pci_set_master()</function> if necessary, too.</para></listitem> | |
1da177e4 LT |
5693 | <listitem><para>Re-initialize the chip.</para></listitem> |
5694 | <listitem><para>Restore the saved registers if necessary.</para></listitem> | |
5695 | <listitem><para>Resume the mixer, e.g. calling | |
5696 | <function>snd_ac97_resume()</function>.</para></listitem> | |
5697 | <listitem><para>Restart the hardware (if any).</para></listitem> | |
5fe76e4d TI |
5698 | <listitem><para>Call <function>snd_power_change_state()</function> with |
5699 | <constant>SNDRV_CTL_POWER_D0</constant> to notify the processes.</para></listitem> | |
1da177e4 LT |
5700 | </orderedlist> |
5701 | </para> | |
5702 | ||
5703 | <para> | |
5704 | A typical code would be like: | |
5705 | ||
5706 | <informalexample> | |
5707 | <programlisting> | |
5708 | <![CDATA[ | |
5fe76e4d | 5709 | static int mychip_resume(struct pci_dev *pci) |
1da177e4 LT |
5710 | { |
5711 | /* (1) */ | |
5fe76e4d TI |
5712 | struct snd_card *card = pci_get_drvdata(pci); |
5713 | struct mychip *chip = card->private_data; | |
1da177e4 | 5714 | /* (2) */ |
5fe76e4d TI |
5715 | pci_restore_state(pci); |
5716 | pci_enable_device(pci); | |
5717 | pci_set_master(pci); | |
1da177e4 LT |
5718 | /* (3) */ |
5719 | snd_mychip_reinit_chip(chip); | |
5720 | /* (4) */ | |
5721 | snd_mychip_restore_registers(chip); | |
5722 | /* (5) */ | |
5723 | snd_ac97_resume(chip->ac97); | |
5724 | /* (6) */ | |
5725 | snd_mychip_restart_chip(chip); | |
5fe76e4d TI |
5726 | /* (7) */ |
5727 | snd_power_change_state(card, SNDRV_CTL_POWER_D0); | |
1da177e4 LT |
5728 | return 0; |
5729 | } | |
5730 | ]]> | |
5731 | </programlisting> | |
5732 | </informalexample> | |
5733 | </para> | |
5734 | ||
5735 | <para> | |
5fe76e4d TI |
5736 | As shown in the above, it's better to save registers after |
5737 | suspending the PCM operations via | |
5738 | <function>snd_pcm_suspend_all()</function> or | |
5739 | <function>snd_pcm_suspend()</function>. It means that the PCM | |
0ba4f6e4 | 5740 | streams are already stopped when the register snapshot is |
3f03f7c5 | 5741 | taken. But, remember that you don't have to restart the PCM |
5fe76e4d TI |
5742 | stream in the resume callback. It'll be restarted via |
5743 | trigger call with <constant>SNDRV_PCM_TRIGGER_RESUME</constant> | |
5744 | when necessary. | |
5745 | </para> | |
5746 | ||
5747 | <para> | |
5748 | OK, we have all callbacks now. Let's set them up. In the | |
5749 | initialization of the card, make sure that you can get the chip | |
5750 | data from the card instance, typically via | |
5751 | <structfield>private_data</structfield> field, in case you | |
5752 | created the chip data individually. | |
5753 | ||
5754 | <informalexample> | |
5755 | <programlisting> | |
5756 | <![CDATA[ | |
090015ae TI |
5757 | static int snd_mychip_probe(struct pci_dev *pci, |
5758 | const struct pci_device_id *pci_id) | |
5fe76e4d TI |
5759 | { |
5760 | .... | |
5761 | struct snd_card *card; | |
5762 | struct mychip *chip; | |
d453379b | 5763 | int err; |
5fe76e4d | 5764 | .... |
393aa9c1 TI |
5765 | err = snd_card_new(&pci->dev, index[dev], id[dev], THIS_MODULE, |
5766 | 0, &card); | |
5fe76e4d TI |
5767 | .... |
5768 | chip = kzalloc(sizeof(*chip), GFP_KERNEL); | |
5769 | .... | |
5770 | card->private_data = chip; | |
5771 | .... | |
5772 | } | |
5773 | ]]> | |
5774 | </programlisting> | |
5775 | </informalexample> | |
5776 | ||
5777 | When you created the chip data with | |
393aa9c1 | 5778 | <function>snd_card_new()</function>, it's anyway accessible |
5fe76e4d | 5779 | via <structfield>private_data</structfield> field. |
1da177e4 LT |
5780 | |
5781 | <informalexample> | |
5782 | <programlisting> | |
5783 | <![CDATA[ | |
090015ae TI |
5784 | static int snd_mychip_probe(struct pci_dev *pci, |
5785 | const struct pci_device_id *pci_id) | |
1da177e4 LT |
5786 | { |
5787 | .... | |
446ab5f5 TI |
5788 | struct snd_card *card; |
5789 | struct mychip *chip; | |
d453379b | 5790 | int err; |
1da177e4 | 5791 | .... |
393aa9c1 TI |
5792 | err = snd_card_new(&pci->dev, index[dev], id[dev], THIS_MODULE, |
5793 | sizeof(struct mychip), &card); | |
5fe76e4d TI |
5794 | .... |
5795 | chip = card->private_data; | |
1da177e4 LT |
5796 | .... |
5797 | } | |
5798 | ]]> | |
5799 | </programlisting> | |
5800 | </informalexample> | |
5801 | ||
1da177e4 LT |
5802 | </para> |
5803 | ||
5804 | <para> | |
3f03f7c5 | 5805 | If you need a space to save the registers, allocate the |
5fe76e4d | 5806 | buffer for it here, too, since it would be fatal |
1da177e4 LT |
5807 | if you cannot allocate a memory in the suspend phase. |
5808 | The allocated buffer should be released in the corresponding | |
5809 | destructor. | |
5810 | </para> | |
5811 | ||
5812 | <para> | |
5fe76e4d | 5813 | And next, set suspend/resume callbacks to the pci_driver. |
1da177e4 LT |
5814 | |
5815 | <informalexample> | |
5816 | <programlisting> | |
5817 | <![CDATA[ | |
5818 | static struct pci_driver driver = { | |
ce1fd369 | 5819 | .name = KBUILD_MODNAME, |
1da177e4 LT |
5820 | .id_table = snd_my_ids, |
5821 | .probe = snd_my_probe, | |
090015ae | 5822 | .remove = snd_my_remove, |
5fe76e4d TI |
5823 | #ifdef CONFIG_PM |
5824 | .suspend = snd_my_suspend, | |
5825 | .resume = snd_my_resume, | |
5826 | #endif | |
1da177e4 LT |
5827 | }; |
5828 | ]]> | |
5829 | </programlisting> | |
5830 | </informalexample> | |
5831 | </para> | |
5832 | ||
5833 | </chapter> | |
5834 | ||
5835 | ||
5836 | <!-- ****************************************************** --> | |
5837 | <!-- Module Parameters --> | |
5838 | <!-- ****************************************************** --> | |
5839 | <chapter id="module-parameters"> | |
5840 | <title>Module Parameters</title> | |
5841 | <para> | |
5842 | There are standard module options for ALSA. At least, each | |
3f03f7c5 | 5843 | module should have the <parameter>index</parameter>, |
1da177e4 LT |
5844 | <parameter>id</parameter> and <parameter>enable</parameter> |
5845 | options. | |
5846 | </para> | |
5847 | ||
5848 | <para> | |
5849 | If the module supports multiple cards (usually up to | |
5850 | 8 = <constant>SNDRV_CARDS</constant> cards), they should be | |
3f03f7c5 MO |
5851 | arrays. The default initial values are defined already as |
5852 | constants for easier programming: | |
1da177e4 LT |
5853 | |
5854 | <informalexample> | |
5855 | <programlisting> | |
5856 | <![CDATA[ | |
5857 | static int index[SNDRV_CARDS] = SNDRV_DEFAULT_IDX; | |
5858 | static char *id[SNDRV_CARDS] = SNDRV_DEFAULT_STR; | |
5859 | static int enable[SNDRV_CARDS] = SNDRV_DEFAULT_ENABLE_PNP; | |
5860 | ]]> | |
5861 | </programlisting> | |
5862 | </informalexample> | |
5863 | </para> | |
5864 | ||
5865 | <para> | |
5866 | If the module supports only a single card, they could be single | |
5867 | variables, instead. <parameter>enable</parameter> option is not | |
3f03f7c5 | 5868 | always necessary in this case, but it would be better to have a |
1da177e4 LT |
5869 | dummy option for compatibility. |
5870 | </para> | |
5871 | ||
5872 | <para> | |
5873 | The module parameters must be declared with the standard | |
5874 | <function>module_param()()</function>, | |
5875 | <function>module_param_array()()</function> and | |
5876 | <function>MODULE_PARM_DESC()</function> macros. | |
5877 | </para> | |
5878 | ||
5879 | <para> | |
5880 | The typical coding would be like below: | |
5881 | ||
5882 | <informalexample> | |
5883 | <programlisting> | |
5884 | <![CDATA[ | |
5885 | #define CARD_NAME "My Chip" | |
5886 | ||
5887 | module_param_array(index, int, NULL, 0444); | |
5888 | MODULE_PARM_DESC(index, "Index value for " CARD_NAME " soundcard."); | |
5889 | module_param_array(id, charp, NULL, 0444); | |
5890 | MODULE_PARM_DESC(id, "ID string for " CARD_NAME " soundcard."); | |
5891 | module_param_array(enable, bool, NULL, 0444); | |
5892 | MODULE_PARM_DESC(enable, "Enable " CARD_NAME " soundcard."); | |
5893 | ]]> | |
5894 | </programlisting> | |
5895 | </informalexample> | |
5896 | </para> | |
5897 | ||
5898 | <para> | |
5899 | Also, don't forget to define the module description, classes, | |
5900 | license and devices. Especially, the recent modprobe requires to | |
5901 | define the module license as GPL, etc., otherwise the system is | |
5902 | shown as <quote>tainted</quote>. | |
5903 | ||
5904 | <informalexample> | |
5905 | <programlisting> | |
5906 | <![CDATA[ | |
5907 | MODULE_DESCRIPTION("My Chip"); | |
5908 | MODULE_LICENSE("GPL"); | |
5909 | MODULE_SUPPORTED_DEVICE("{{Vendor,My Chip Name}}"); | |
5910 | ]]> | |
5911 | </programlisting> | |
5912 | </informalexample> | |
5913 | </para> | |
5914 | ||
5915 | </chapter> | |
5916 | ||
5917 | ||
5918 | <!-- ****************************************************** --> | |
5919 | <!-- How To Put Your Driver --> | |
5920 | <!-- ****************************************************** --> | |
5921 | <chapter id="how-to-put-your-driver"> | |
5922 | <title>How To Put Your Driver Into ALSA Tree</title> | |
5923 | <section> | |
5924 | <title>General</title> | |
5925 | <para> | |
5926 | So far, you've learned how to write the driver codes. | |
5927 | And you might have a question now: how to put my own | |
5928 | driver into the ALSA driver tree? | |
5929 | Here (finally :) the standard procedure is described briefly. | |
5930 | </para> | |
5931 | ||
5932 | <para> | |
3f03f7c5 | 5933 | Suppose that you create a new PCI driver for the card |
1da177e4 | 5934 | <quote>xyz</quote>. The card module name would be |
3f03f7c5 | 5935 | snd-xyz. The new driver is usually put into the alsa-driver |
1da177e4 LT |
5936 | tree, <filename>alsa-driver/pci</filename> directory in |
5937 | the case of PCI cards. | |
5938 | Then the driver is evaluated, audited and tested | |
5939 | by developers and users. After a certain time, the driver | |
3f03f7c5 | 5940 | will go to the alsa-kernel tree (to the corresponding directory, |
1da177e4 | 5941 | such as <filename>alsa-kernel/pci</filename>) and eventually |
3f03f7c5 | 5942 | will be integrated into the Linux 2.6 tree (the directory would be |
1da177e4 LT |
5943 | <filename>linux/sound/pci</filename>). |
5944 | </para> | |
5945 | ||
5946 | <para> | |
5947 | In the following sections, the driver code is supposed | |
3f03f7c5 | 5948 | to be put into alsa-driver tree. The two cases are covered: |
1da177e4 LT |
5949 | a driver consisting of a single source file and one consisting |
5950 | of several source files. | |
5951 | </para> | |
5952 | </section> | |
5953 | ||
5954 | <section> | |
5955 | <title>Driver with A Single Source File</title> | |
5956 | <para> | |
5957 | <orderedlist> | |
5958 | <listitem> | |
5959 | <para> | |
5960 | Modify alsa-driver/pci/Makefile | |
5961 | </para> | |
5962 | ||
5963 | <para> | |
5964 | Suppose you have a file xyz.c. Add the following | |
5965 | two lines | |
5966 | <informalexample> | |
5967 | <programlisting> | |
5968 | <![CDATA[ | |
5969 | snd-xyz-objs := xyz.o | |
5970 | obj-$(CONFIG_SND_XYZ) += snd-xyz.o | |
5971 | ]]> | |
5972 | </programlisting> | |
5973 | </informalexample> | |
5974 | </para> | |
5975 | </listitem> | |
5976 | ||
5977 | <listitem> | |
5978 | <para> | |
5979 | Create the Kconfig entry | |
5980 | </para> | |
5981 | ||
5982 | <para> | |
5983 | Add the new entry of Kconfig for your xyz driver. | |
5984 | <informalexample> | |
5985 | <programlisting> | |
5986 | <![CDATA[ | |
5987 | config SND_XYZ | |
5988 | tristate "Foobar XYZ" | |
5989 | depends on SND | |
5990 | select SND_PCM | |
5991 | help | |
5992 | Say Y here to include support for Foobar XYZ soundcard. | |
5993 | ||
5994 | To compile this driver as a module, choose M here: the module | |
5995 | will be called snd-xyz. | |
5996 | ]]> | |
5997 | </programlisting> | |
5998 | </informalexample> | |
5999 | ||
6000 | the line, select SND_PCM, specifies that the driver xyz supports | |
6001 | PCM. In addition to SND_PCM, the following components are | |
6002 | supported for select command: | |
6003 | SND_RAWMIDI, SND_TIMER, SND_HWDEP, SND_MPU401_UART, | |
6004 | SND_OPL3_LIB, SND_OPL4_LIB, SND_VX_LIB, SND_AC97_CODEC. | |
6005 | Add the select command for each supported component. | |
6006 | </para> | |
6007 | ||
6008 | <para> | |
6009 | Note that some selections imply the lowlevel selections. | |
6010 | For example, PCM includes TIMER, MPU401_UART includes RAWMIDI, | |
6011 | AC97_CODEC includes PCM, and OPL3_LIB includes HWDEP. | |
6012 | You don't need to give the lowlevel selections again. | |
6013 | </para> | |
6014 | ||
6015 | <para> | |
6016 | For the details of Kconfig script, refer to the kbuild | |
6017 | documentation. | |
6018 | </para> | |
6019 | ||
6020 | </listitem> | |
6021 | ||
6022 | <listitem> | |
6023 | <para> | |
6024 | Run cvscompile script to re-generate the configure script and | |
6025 | build the whole stuff again. | |
6026 | </para> | |
6027 | </listitem> | |
6028 | </orderedlist> | |
6029 | </para> | |
6030 | </section> | |
6031 | ||
6032 | <section> | |
6033 | <title>Drivers with Several Source Files</title> | |
6034 | <para> | |
6035 | Suppose that the driver snd-xyz have several source files. | |
6036 | They are located in the new subdirectory, | |
6037 | pci/xyz. | |
6038 | ||
6039 | <orderedlist> | |
6040 | <listitem> | |
6041 | <para> | |
6042 | Add a new directory (<filename>xyz</filename>) in | |
3f03f7c5 | 6043 | <filename>alsa-driver/pci/Makefile</filename> as below |
1da177e4 LT |
6044 | |
6045 | <informalexample> | |
6046 | <programlisting> | |
6047 | <![CDATA[ | |
6048 | obj-$(CONFIG_SND) += xyz/ | |
6049 | ]]> | |
6050 | </programlisting> | |
6051 | </informalexample> | |
6052 | </para> | |
6053 | </listitem> | |
6054 | ||
6055 | <listitem> | |
6056 | <para> | |
6057 | Under the directory <filename>xyz</filename>, create a Makefile | |
6058 | ||
6059 | <example> | |
6060 | <title>Sample Makefile for a driver xyz</title> | |
6061 | <programlisting> | |
6062 | <![CDATA[ | |
6063 | ifndef SND_TOPDIR | |
6064 | SND_TOPDIR=../.. | |
6065 | endif | |
6066 | ||
6067 | include $(SND_TOPDIR)/toplevel.config | |
6068 | include $(SND_TOPDIR)/Makefile.conf | |
6069 | ||
6070 | snd-xyz-objs := xyz.o abc.o def.o | |
6071 | ||
6072 | obj-$(CONFIG_SND_XYZ) += snd-xyz.o | |
6073 | ||
6074 | include $(SND_TOPDIR)/Rules.make | |
6075 | ]]> | |
6076 | </programlisting> | |
6077 | </example> | |
6078 | </para> | |
6079 | </listitem> | |
6080 | ||
6081 | <listitem> | |
6082 | <para> | |
6083 | Create the Kconfig entry | |
6084 | </para> | |
6085 | ||
6086 | <para> | |
6087 | This procedure is as same as in the last section. | |
6088 | </para> | |
6089 | </listitem> | |
6090 | ||
6091 | <listitem> | |
6092 | <para> | |
6093 | Run cvscompile script to re-generate the configure script and | |
6094 | build the whole stuff again. | |
6095 | </para> | |
6096 | </listitem> | |
6097 | </orderedlist> | |
6098 | </para> | |
6099 | </section> | |
6100 | ||
6101 | </chapter> | |
6102 | ||
6103 | <!-- ****************************************************** --> | |
6104 | <!-- Useful Functions --> | |
6105 | <!-- ****************************************************** --> | |
6106 | <chapter id="useful-functions"> | |
6107 | <title>Useful Functions</title> | |
6108 | ||
6109 | <section id="useful-functions-snd-printk"> | |
6110 | <title><function>snd_printk()</function> and friends</title> | |
6111 | <para> | |
3f03f7c5 | 6112 | ALSA provides a verbose version of the |
1da177e4 LT |
6113 | <function>printk()</function> function. If a kernel config |
6114 | <constant>CONFIG_SND_VERBOSE_PRINTK</constant> is set, this | |
6115 | function prints the given message together with the file name | |
6116 | and the line of the caller. The <constant>KERN_XXX</constant> | |
6117 | prefix is processed as | |
6118 | well as the original <function>printk()</function> does, so it's | |
6119 | recommended to add this prefix, e.g. | |
6120 | ||
6121 | <informalexample> | |
6122 | <programlisting> | |
6123 | <![CDATA[ | |
6124 | snd_printk(KERN_ERR "Oh my, sorry, it's extremely bad!\n"); | |
6125 | ]]> | |
6126 | </programlisting> | |
6127 | </informalexample> | |
6128 | </para> | |
6129 | ||
6130 | <para> | |
6131 | There are also <function>printk()</function>'s for | |
6132 | debugging. <function>snd_printd()</function> can be used for | |
6133 | general debugging purposes. If | |
6134 | <constant>CONFIG_SND_DEBUG</constant> is set, this function is | |
6135 | compiled, and works just like | |
6136 | <function>snd_printk()</function>. If the ALSA is compiled | |
6137 | without the debugging flag, it's ignored. | |
6138 | </para> | |
6139 | ||
6140 | <para> | |
6141 | <function>snd_printdd()</function> is compiled in only when | |
62cf872a TI |
6142 | <constant>CONFIG_SND_DEBUG_VERBOSE</constant> is set. Please note |
6143 | that <constant>CONFIG_SND_DEBUG_VERBOSE</constant> is not set as default | |
1da177e4 LT |
6144 | even if you configure the alsa-driver with |
6145 | <option>--with-debug=full</option> option. You need to give | |
6146 | explicitly <option>--with-debug=detect</option> option instead. | |
6147 | </para> | |
6148 | </section> | |
6149 | ||
1da177e4 LT |
6150 | <section id="useful-functions-snd-bug"> |
6151 | <title><function>snd_BUG()</function></title> | |
1da177e4 | 6152 | <para> |
3f03f7c5 | 6153 | It shows the <computeroutput>BUG?</computeroutput> message and |
7cc6dffd | 6154 | stack trace as well as <function>snd_BUG_ON</function> at the point. |
7c22f1aa TI |
6155 | It's useful to show that a fatal error happens there. |
6156 | </para> | |
6157 | <para> | |
6158 | When no debug flag is set, this macro is ignored. | |
1da177e4 LT |
6159 | </para> |
6160 | </section> | |
5ef03460 TI |
6161 | |
6162 | <section id="useful-functions-snd-bug-on"> | |
6163 | <title><function>snd_BUG_ON()</function></title> | |
6164 | <para> | |
6165 | <function>snd_BUG_ON()</function> macro is similar with | |
6166 | <function>WARN_ON()</function> macro. For example, | |
1da177e4 LT |
6167 | |
6168 | <informalexample> | |
6169 | <programlisting> | |
6170 | <![CDATA[ | |
5ef03460 | 6171 | snd_BUG_ON(!pointer); |
1da177e4 LT |
6172 | ]]> |
6173 | </programlisting> | |
6174 | </informalexample> | |
1da177e4 | 6175 | |
5ef03460 TI |
6176 | or it can be used as the condition, |
6177 | <informalexample> | |
6178 | <programlisting> | |
6179 | <![CDATA[ | |
6180 | if (snd_BUG_ON(non_zero_is_bug)) | |
6181 | return -EINVAL; | |
6182 | ]]> | |
6183 | </programlisting> | |
6184 | </informalexample> | |
1da177e4 | 6185 | |
7c22f1aa | 6186 | </para> |
5ef03460 | 6187 | |
7c22f1aa | 6188 | <para> |
5ef03460 | 6189 | The macro takes an conditional expression to evaluate. |
d5702162 CS |
6190 | When <constant>CONFIG_SND_DEBUG</constant>, is set, if the |
6191 | expression is non-zero, it shows the warning message such as | |
5ef03460 | 6192 | <computeroutput>BUG? (xxx)</computeroutput> |
d5702162 CS |
6193 | normally followed by stack trace. |
6194 | ||
6195 | In both cases it returns the evaluated value. | |
1da177e4 | 6196 | </para> |
5ef03460 | 6197 | |
1da177e4 | 6198 | </section> |
5ef03460 | 6199 | |
1da177e4 LT |
6200 | </chapter> |
6201 | ||
6202 | ||
6203 | <!-- ****************************************************** --> | |
6204 | <!-- Acknowledgments --> | |
6205 | <!-- ****************************************************** --> | |
5bda9fa1 | 6206 | <chapter id="acknowledgments"> |
1da177e4 LT |
6207 | <title>Acknowledgments</title> |
6208 | <para> | |
6209 | I would like to thank Phil Kerr for his help for improvement and | |
6210 | corrections of this document. | |
6211 | </para> | |
6212 | <para> | |
6213 | Kevin Conder reformatted the original plain-text to the | |
6214 | DocBook format. | |
6215 | </para> | |
6216 | <para> | |
6217 | Giuliano Pochini corrected typos and contributed the example codes | |
6218 | in the hardware constraints section. | |
6219 | </para> | |
6220 | </chapter> | |
1da177e4 | 6221 | </book> |