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1 | <!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook V4.1//EN"> |
2 | ||
3 | <book> | |
4 | <?dbhtml filename="index.html"> | |
5 | ||
6 | <!-- ****************************************************** --> | |
7 | <!-- Header --> | |
8 | <!-- ****************************************************** --> | |
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 | ||
5fe76e4d TI |
21 | <date>November 17, 2005</date> |
22 | <edition>0.3.6</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> | |
70 | driver. The document focuses mainly on the PCI soundcard. | |
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> | |
78 | The target of this document is ones who already have enough | |
79 | skill of C language and have the basic knowledge of linux | |
80 | kernel programming. This document doesn't explain the general | |
81 | topics of linux kernel codes and doesn't cover the detail of | |
82 | implementation of each low-level driver. It describes only how is | |
83 | the standard way to write a PCI sound driver on ALSA. | |
84 | </para> | |
85 | ||
86 | <para> | |
87 | If you are already familiar with the older ALSA ver.0.5.x, you | |
88 | can check the drivers such as <filename>es1938.c</filename> or | |
89 | <filename>maestro3.c</filename> which have also almost the same | |
90 | code-base in the ALSA 0.5.x tree, so you can compare the differences. | |
91 | </para> | |
92 | ||
93 | <para> | |
94 | This document is still a draft version. Any feedbacks and | |
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> | |
109 | The ALSA drivers are provided in the two ways. | |
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 | |
117 | contains purely the source codes for the Linux 2.6 (or later) | |
118 | tree. This tree is designed only for compilation on 2.6 or | |
119 | later environment. The latter, alsa-driver, contains many subtle | |
120 | files for compiling the ALSA driver on the outside of Linux | |
121 | kernel like configure script, the wrapper functions for older, | |
122 | 2.2 and 2.4 kernels, to adapt the latest kernel API, | |
123 | and additional drivers which are still in development or in | |
124 | tests. The drivers in alsa-driver tree will be moved to | |
125 | alsa-kernel (eventually 2.6 kernel tree) once when they are | |
126 | finished and confirmed to work fine. | |
127 | </para> | |
128 | ||
129 | <para> | |
130 | The file tree structure of ALSA driver is depicted below. Both | |
131 | alsa-kernel and alsa-driver have almost the same file | |
132 | structure, except for <quote>core</quote> directory. It's | |
133 | named as <quote>acore</quote> in alsa-driver tree. | |
134 | ||
135 | <example> | |
136 | <title>ALSA File Tree Structure</title> | |
137 | <literallayout> | |
138 | sound | |
139 | /core | |
140 | /oss | |
141 | /seq | |
142 | /oss | |
143 | /instr | |
144 | /ioctl32 | |
145 | /include | |
146 | /drivers | |
147 | /mpu401 | |
148 | /opl3 | |
149 | /i2c | |
150 | /l3 | |
151 | /synth | |
152 | /emux | |
153 | /pci | |
154 | /(cards) | |
155 | /isa | |
156 | /(cards) | |
157 | /arm | |
158 | /ppc | |
159 | /sparc | |
160 | /usb | |
161 | /pcmcia /(cards) | |
162 | /oss | |
163 | </literallayout> | |
164 | </example> | |
165 | </para> | |
166 | </section> | |
167 | ||
168 | <section id="file-tree-core-directory"> | |
169 | <title>core directory</title> | |
170 | <para> | |
171 | This directory contains the middle layer, that is, the heart | |
172 | of ALSA drivers. In this directory, the native ALSA modules are | |
173 | stored. The sub-directories contain different modules and are | |
174 | dependent upon the kernel config. | |
175 | </para> | |
176 | ||
177 | <section id="file-tree-core-directory-oss"> | |
178 | <title>core/oss</title> | |
179 | ||
180 | <para> | |
181 | The codes for PCM and mixer OSS emulation modules are stored | |
182 | in this directory. The rawmidi OSS emulation is included in | |
183 | the ALSA rawmidi code since it's quite small. The sequencer | |
184 | code is stored in core/seq/oss directory (see | |
185 | <link linkend="file-tree-core-directory-seq-oss"><citetitle> | |
186 | below</citetitle></link>). | |
187 | </para> | |
188 | </section> | |
189 | ||
190 | <section id="file-tree-core-directory-ioctl32"> | |
191 | <title>core/ioctl32</title> | |
192 | ||
193 | <para> | |
194 | This directory contains the 32bit-ioctl wrappers for 64bit | |
195 | architectures such like x86-64, ppc64 and sparc64. For 32bit | |
196 | and alpha architectures, these are not compiled. | |
197 | </para> | |
198 | </section> | |
199 | ||
200 | <section id="file-tree-core-directory-seq"> | |
201 | <title>core/seq</title> | |
202 | <para> | |
203 | This and its sub-directories are for the ALSA | |
204 | sequencer. This directory contains the sequencer core and | |
205 | primary sequencer modules such like snd-seq-midi, | |
206 | snd-seq-virmidi, etc. They are compiled only when | |
207 | <constant>CONFIG_SND_SEQUENCER</constant> is set in the kernel | |
208 | config. | |
209 | </para> | |
210 | </section> | |
211 | ||
212 | <section id="file-tree-core-directory-seq-oss"> | |
213 | <title>core/seq/oss</title> | |
214 | <para> | |
215 | This contains the OSS sequencer emulation codes. | |
216 | </para> | |
217 | </section> | |
218 | ||
219 | <section id="file-tree-core-directory-deq-instr"> | |
220 | <title>core/seq/instr</title> | |
221 | <para> | |
222 | This directory contains the modules for the sequencer | |
223 | instrument layer. | |
224 | </para> | |
225 | </section> | |
226 | </section> | |
227 | ||
228 | <section id="file-tree-include-directory"> | |
229 | <title>include directory</title> | |
230 | <para> | |
231 | This is the place for the public header files of ALSA drivers, | |
232 | which are to be exported to the user-space, or included by | |
233 | several files at different directories. Basically, the private | |
234 | header files should not be placed in this directory, but you may | |
235 | still find files there, due to historical reason :) | |
236 | </para> | |
237 | </section> | |
238 | ||
239 | <section id="file-tree-drivers-directory"> | |
240 | <title>drivers directory</title> | |
241 | <para> | |
242 | This directory contains the codes shared among different drivers | |
243 | on the different architectures. They are hence supposed not to be | |
244 | architecture-specific. | |
245 | For example, the dummy pcm driver and the serial MIDI | |
246 | driver are found in this directory. In the sub-directories, | |
247 | there are the codes for components which are independent from | |
248 | bus and cpu architectures. | |
249 | </para> | |
250 | ||
251 | <section id="file-tree-drivers-directory-mpu401"> | |
252 | <title>drivers/mpu401</title> | |
253 | <para> | |
254 | The MPU401 and MPU401-UART modules are stored here. | |
255 | </para> | |
256 | </section> | |
257 | ||
258 | <section id="file-tree-drivers-directory-opl3"> | |
259 | <title>drivers/opl3 and opl4</title> | |
260 | <para> | |
261 | The OPL3 and OPL4 FM-synth stuff is found here. | |
262 | </para> | |
263 | </section> | |
264 | </section> | |
265 | ||
266 | <section id="file-tree-i2c-directory"> | |
267 | <title>i2c directory</title> | |
268 | <para> | |
269 | This contains the ALSA i2c components. | |
270 | </para> | |
271 | ||
272 | <para> | |
273 | Although there is a standard i2c layer on Linux, ALSA has its | |
274 | own i2c codes for some cards, because the soundcard needs only a | |
275 | simple operation and the standard i2c API is too complicated for | |
276 | such a purpose. | |
277 | </para> | |
278 | ||
279 | <section id="file-tree-i2c-directory-l3"> | |
280 | <title>i2c/l3</title> | |
281 | <para> | |
282 | This is a sub-directory for ARM L3 i2c. | |
283 | </para> | |
284 | </section> | |
285 | </section> | |
286 | ||
287 | <section id="file-tree-synth-directory"> | |
288 | <title>synth directory</title> | |
289 | <para> | |
290 | This contains the synth middle-level modules. | |
291 | </para> | |
292 | ||
293 | <para> | |
294 | So far, there is only Emu8000/Emu10k1 synth driver under | |
295 | synth/emux sub-directory. | |
296 | </para> | |
297 | </section> | |
298 | ||
299 | <section id="file-tree-pci-directory"> | |
300 | <title>pci directory</title> | |
301 | <para> | |
302 | This and its sub-directories hold the top-level card modules | |
303 | for PCI soundcards and the codes specific to the PCI BUS. | |
304 | </para> | |
305 | ||
306 | <para> | |
307 | The drivers compiled from a single file is stored directly on | |
308 | pci directory, while the drivers with several source files are | |
309 | stored on its own sub-directory (e.g. emu10k1, ice1712). | |
310 | </para> | |
311 | </section> | |
312 | ||
313 | <section id="file-tree-isa-directory"> | |
314 | <title>isa directory</title> | |
315 | <para> | |
316 | This and its sub-directories hold the top-level card modules | |
317 | for ISA soundcards. | |
318 | </para> | |
319 | </section> | |
320 | ||
321 | <section id="file-tree-arm-ppc-sparc-directories"> | |
322 | <title>arm, ppc, and sparc directories</title> | |
323 | <para> | |
324 | These are for the top-level card modules which are | |
325 | specific to each given architecture. | |
326 | </para> | |
327 | </section> | |
328 | ||
329 | <section id="file-tree-usb-directory"> | |
330 | <title>usb directory</title> | |
331 | <para> | |
332 | This contains the USB-audio driver. On the latest version, the | |
333 | USB MIDI driver is integrated together with usb-audio driver. | |
334 | </para> | |
335 | </section> | |
336 | ||
337 | <section id="file-tree-pcmcia-directory"> | |
338 | <title>pcmcia directory</title> | |
339 | <para> | |
340 | The PCMCIA, especially PCCard drivers will go here. CardBus | |
341 | drivers will be on pci directory, because its API is identical | |
342 | with the standard PCI cards. | |
343 | </para> | |
344 | </section> | |
345 | ||
346 | <section id="file-tree-oss-directory"> | |
347 | <title>oss directory</title> | |
348 | <para> | |
349 | The OSS/Lite source files are stored here on Linux 2.6 (or | |
350 | later) tree. (In the ALSA driver tarball, it's empty, of course :) | |
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> | |
365 | The minimum flow of PCI soundcard is like the following: | |
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> | |
373 | <listitem><para>create pci_driver table which contains the three pointers above.</para></listitem> | |
01d25d46 | 374 | <listitem><para>create <function>init()</function> function just calling <function>pci_register_driver()</function> to register the pci_driver table defined above.</para></listitem> |
1da177e4 LT |
375 | <listitem><para>create <function>exit()</function> function to call <function>pci_unregister_driver()</function> function.</para></listitem> |
376 | </itemizedlist> | |
377 | </para> | |
378 | </section> | |
379 | ||
380 | <section id="basic-flow-example"> | |
381 | <title>Full Code Example</title> | |
382 | <para> | |
383 | The code example is shown below. Some parts are kept | |
384 | unimplemented at this moment but will be filled in the | |
385 | succeeding sections. The numbers in comment lines of | |
386 | <function>snd_mychip_probe()</function> function are the | |
387 | markers. | |
388 | ||
389 | <example> | |
390 | <title>Basic Flow for PCI Drivers Example</title> | |
391 | <programlisting> | |
392 | <![CDATA[ | |
393 | #include <sound/driver.h> | |
394 | #include <linux/init.h> | |
395 | #include <linux/pci.h> | |
396 | #include <linux/slab.h> | |
397 | #include <sound/core.h> | |
398 | #include <sound/initval.h> | |
399 | ||
400 | /* module parameters (see "Module Parameters") */ | |
401 | static int index[SNDRV_CARDS] = SNDRV_DEFAULT_IDX; | |
402 | static char *id[SNDRV_CARDS] = SNDRV_DEFAULT_STR; | |
403 | static int enable[SNDRV_CARDS] = SNDRV_DEFAULT_ENABLE_PNP; | |
404 | ||
405 | /* definition of the chip-specific record */ | |
446ab5f5 TI |
406 | struct mychip { |
407 | struct snd_card *card; | |
1da177e4 LT |
408 | // rest of implementation will be in the section |
409 | // "PCI Resource Managements" | |
410 | }; | |
411 | ||
412 | /* chip-specific destructor | |
413 | * (see "PCI Resource Managements") | |
414 | */ | |
446ab5f5 | 415 | static int snd_mychip_free(struct mychip *chip) |
1da177e4 LT |
416 | { |
417 | .... // will be implemented later... | |
418 | } | |
419 | ||
420 | /* component-destructor | |
421 | * (see "Management of Cards and Components") | |
422 | */ | |
446ab5f5 | 423 | static int snd_mychip_dev_free(struct snd_device *device) |
1da177e4 | 424 | { |
446ab5f5 | 425 | return snd_mychip_free(device->device_data); |
1da177e4 LT |
426 | } |
427 | ||
428 | /* chip-specific constructor | |
429 | * (see "Management of Cards and Components") | |
430 | */ | |
446ab5f5 | 431 | static int __devinit snd_mychip_create(struct snd_card *card, |
1da177e4 | 432 | struct pci_dev *pci, |
446ab5f5 | 433 | struct mychip **rchip) |
1da177e4 | 434 | { |
446ab5f5 | 435 | struct mychip *chip; |
1da177e4 | 436 | int err; |
446ab5f5 | 437 | static struct snd_device_ops ops = { |
1da177e4 LT |
438 | .dev_free = snd_mychip_dev_free, |
439 | }; | |
440 | ||
441 | *rchip = NULL; | |
442 | ||
443 | // check PCI availability here | |
444 | // (see "PCI Resource Managements") | |
445 | .... | |
446 | ||
447 | /* allocate a chip-specific data with zero filled */ | |
561b220a | 448 | chip = kzalloc(sizeof(*chip), GFP_KERNEL); |
1da177e4 LT |
449 | if (chip == NULL) |
450 | return -ENOMEM; | |
451 | ||
452 | chip->card = card; | |
453 | ||
454 | // rest of initialization here; will be implemented | |
455 | // later, see "PCI Resource Managements" | |
456 | .... | |
457 | ||
458 | if ((err = snd_device_new(card, SNDRV_DEV_LOWLEVEL, | |
459 | chip, &ops)) < 0) { | |
460 | snd_mychip_free(chip); | |
461 | return err; | |
462 | } | |
463 | ||
464 | snd_card_set_dev(card, &pci->dev); | |
465 | ||
466 | *rchip = chip; | |
467 | return 0; | |
468 | } | |
469 | ||
470 | /* constructor -- see "Constructor" sub-section */ | |
471 | static int __devinit snd_mychip_probe(struct pci_dev *pci, | |
472 | const struct pci_device_id *pci_id) | |
473 | { | |
474 | static int dev; | |
446ab5f5 TI |
475 | struct snd_card *card; |
476 | struct mychip *chip; | |
1da177e4 LT |
477 | int err; |
478 | ||
479 | /* (1) */ | |
480 | if (dev >= SNDRV_CARDS) | |
481 | return -ENODEV; | |
482 | if (!enable[dev]) { | |
483 | dev++; | |
484 | return -ENOENT; | |
485 | } | |
486 | ||
487 | /* (2) */ | |
488 | card = snd_card_new(index[dev], id[dev], THIS_MODULE, 0); | |
489 | if (card == NULL) | |
490 | return -ENOMEM; | |
491 | ||
492 | /* (3) */ | |
493 | if ((err = snd_mychip_create(card, pci, &chip)) < 0) { | |
494 | snd_card_free(card); | |
495 | return err; | |
496 | } | |
497 | ||
498 | /* (4) */ | |
499 | strcpy(card->driver, "My Chip"); | |
500 | strcpy(card->shortname, "My Own Chip 123"); | |
501 | sprintf(card->longname, "%s at 0x%lx irq %i", | |
502 | card->shortname, chip->ioport, chip->irq); | |
503 | ||
504 | /* (5) */ | |
505 | .... // implemented later | |
506 | ||
507 | /* (6) */ | |
508 | if ((err = snd_card_register(card)) < 0) { | |
509 | snd_card_free(card); | |
510 | return err; | |
511 | } | |
512 | ||
513 | /* (7) */ | |
514 | pci_set_drvdata(pci, card); | |
515 | dev++; | |
516 | return 0; | |
517 | } | |
518 | ||
519 | /* destructor -- see "Destructor" sub-section */ | |
520 | static void __devexit snd_mychip_remove(struct pci_dev *pci) | |
521 | { | |
522 | snd_card_free(pci_get_drvdata(pci)); | |
523 | pci_set_drvdata(pci, NULL); | |
524 | } | |
525 | ]]> | |
526 | </programlisting> | |
527 | </example> | |
528 | </para> | |
529 | </section> | |
530 | ||
531 | <section id="basic-flow-constructor"> | |
532 | <title>Constructor</title> | |
533 | <para> | |
534 | The real constructor of PCI drivers is probe callback. The | |
535 | probe callback and other component-constructors which are called | |
536 | from probe callback should be defined with | |
537 | <parameter>__devinit</parameter> prefix. You | |
538 | cannot use <parameter>__init</parameter> prefix for them, | |
539 | because any PCI device could be a hotplug device. | |
540 | </para> | |
541 | ||
542 | <para> | |
543 | In the probe callback, the following scheme is often used. | |
544 | </para> | |
545 | ||
546 | <section id="basic-flow-constructor-device-index"> | |
547 | <title>1) Check and increment the device index.</title> | |
548 | <para> | |
549 | <informalexample> | |
550 | <programlisting> | |
551 | <![CDATA[ | |
552 | static int dev; | |
553 | .... | |
554 | if (dev >= SNDRV_CARDS) | |
555 | return -ENODEV; | |
556 | if (!enable[dev]) { | |
557 | dev++; | |
558 | return -ENOENT; | |
559 | } | |
560 | ]]> | |
561 | </programlisting> | |
562 | </informalexample> | |
563 | ||
564 | where enable[dev] is the module option. | |
565 | </para> | |
566 | ||
567 | <para> | |
568 | At each time probe callback is called, check the | |
569 | availability of the device. If not available, simply increment | |
570 | the device index and returns. dev will be incremented also | |
571 | later (<link | |
572 | linkend="basic-flow-constructor-set-pci"><citetitle>step | |
573 | 7</citetitle></link>). | |
574 | </para> | |
575 | </section> | |
576 | ||
577 | <section id="basic-flow-constructor-create-card"> | |
578 | <title>2) Create a card instance</title> | |
579 | <para> | |
580 | <informalexample> | |
581 | <programlisting> | |
582 | <![CDATA[ | |
446ab5f5 | 583 | struct snd_card *card; |
1da177e4 LT |
584 | .... |
585 | card = snd_card_new(index[dev], id[dev], THIS_MODULE, 0); | |
586 | ]]> | |
587 | </programlisting> | |
588 | </informalexample> | |
589 | </para> | |
590 | ||
591 | <para> | |
592 | The detail will be explained in the section | |
593 | <link linkend="card-management-card-instance"><citetitle> | |
594 | Management of Cards and Components</citetitle></link>. | |
595 | </para> | |
596 | </section> | |
597 | ||
598 | <section id="basic-flow-constructor-create-main"> | |
599 | <title>3) Create a main component</title> | |
600 | <para> | |
601 | In this part, the PCI resources are allocated. | |
602 | ||
603 | <informalexample> | |
604 | <programlisting> | |
605 | <![CDATA[ | |
446ab5f5 | 606 | struct mychip *chip; |
1da177e4 LT |
607 | .... |
608 | if ((err = snd_mychip_create(card, pci, &chip)) < 0) { | |
609 | snd_card_free(card); | |
610 | return err; | |
611 | } | |
612 | ]]> | |
613 | </programlisting> | |
614 | </informalexample> | |
615 | ||
616 | The detail will be explained in the section <link | |
617 | linkend="pci-resource"><citetitle>PCI Resource | |
618 | Managements</citetitle></link>. | |
619 | </para> | |
620 | </section> | |
621 | ||
622 | <section id="basic-flow-constructor-main-component"> | |
623 | <title>4) Set the driver ID and name strings.</title> | |
624 | <para> | |
625 | <informalexample> | |
626 | <programlisting> | |
627 | <![CDATA[ | |
628 | strcpy(card->driver, "My Chip"); | |
629 | strcpy(card->shortname, "My Own Chip 123"); | |
630 | sprintf(card->longname, "%s at 0x%lx irq %i", | |
631 | card->shortname, chip->ioport, chip->irq); | |
632 | ]]> | |
633 | </programlisting> | |
634 | </informalexample> | |
635 | ||
636 | The driver field holds the minimal ID string of the | |
637 | chip. This is referred by alsa-lib's configurator, so keep it | |
638 | simple but unique. | |
639 | Even the same driver can have different driver IDs to | |
640 | distinguish the functionality of each chip type. | |
641 | </para> | |
642 | ||
643 | <para> | |
644 | The shortname field is a string shown as more verbose | |
645 | name. The longname field contains the information which is | |
646 | shown in <filename>/proc/asound/cards</filename>. | |
647 | </para> | |
648 | </section> | |
649 | ||
650 | <section id="basic-flow-constructor-create-other"> | |
651 | <title>5) Create other components, such as mixer, MIDI, etc.</title> | |
652 | <para> | |
653 | Here you define the basic components such as | |
654 | <link linkend="pcm-interface"><citetitle>PCM</citetitle></link>, | |
655 | mixer (e.g. <link linkend="api-ac97"><citetitle>AC97</citetitle></link>), | |
656 | MIDI (e.g. <link linkend="midi-interface"><citetitle>MPU-401</citetitle></link>), | |
657 | and other interfaces. | |
658 | Also, if you want a <link linkend="proc-interface"><citetitle>proc | |
659 | file</citetitle></link>, define it here, too. | |
660 | </para> | |
661 | </section> | |
662 | ||
663 | <section id="basic-flow-constructor-register-card"> | |
664 | <title>6) Register the card instance.</title> | |
665 | <para> | |
666 | <informalexample> | |
667 | <programlisting> | |
668 | <![CDATA[ | |
669 | if ((err = snd_card_register(card)) < 0) { | |
670 | snd_card_free(card); | |
671 | return err; | |
672 | } | |
673 | ]]> | |
674 | </programlisting> | |
675 | </informalexample> | |
676 | </para> | |
677 | ||
678 | <para> | |
679 | Will be explained in the section <link | |
680 | linkend="card-management-registration"><citetitle>Management | |
681 | of Cards and Components</citetitle></link>, too. | |
682 | </para> | |
683 | </section> | |
684 | ||
685 | <section id="basic-flow-constructor-set-pci"> | |
686 | <title>7) Set the PCI driver data and return zero.</title> | |
687 | <para> | |
688 | <informalexample> | |
689 | <programlisting> | |
690 | <![CDATA[ | |
691 | pci_set_drvdata(pci, card); | |
692 | dev++; | |
693 | return 0; | |
694 | ]]> | |
695 | </programlisting> | |
696 | </informalexample> | |
697 | ||
698 | In the above, the card record is stored. This pointer is | |
699 | referred in the remove callback and power-management | |
700 | callbacks, too. | |
701 | </para> | |
702 | </section> | |
703 | </section> | |
704 | ||
705 | <section id="basic-flow-destructor"> | |
706 | <title>Destructor</title> | |
707 | <para> | |
708 | The destructor, remove callback, simply releases the card | |
709 | instance. Then the ALSA middle layer will release all the | |
710 | attached components automatically. | |
711 | </para> | |
712 | ||
713 | <para> | |
714 | It would be typically like the following: | |
715 | ||
716 | <informalexample> | |
717 | <programlisting> | |
718 | <![CDATA[ | |
719 | static void __devexit snd_mychip_remove(struct pci_dev *pci) | |
720 | { | |
721 | snd_card_free(pci_get_drvdata(pci)); | |
722 | pci_set_drvdata(pci, NULL); | |
723 | } | |
724 | ]]> | |
725 | </programlisting> | |
726 | </informalexample> | |
727 | ||
728 | The above code assumes that the card pointer is set to the PCI | |
729 | driver data. | |
730 | </para> | |
731 | </section> | |
732 | ||
733 | <section id="basic-flow-header-files"> | |
734 | <title>Header Files</title> | |
735 | <para> | |
736 | For the above example, at least the following include files | |
737 | are necessary. | |
738 | ||
739 | <informalexample> | |
740 | <programlisting> | |
741 | <![CDATA[ | |
742 | #include <sound/driver.h> | |
743 | #include <linux/init.h> | |
744 | #include <linux/pci.h> | |
745 | #include <linux/slab.h> | |
746 | #include <sound/core.h> | |
747 | #include <sound/initval.h> | |
748 | ]]> | |
749 | </programlisting> | |
750 | </informalexample> | |
751 | ||
752 | where the last one is necessary only when module options are | |
753 | defined in the source file. If the codes are split to several | |
754 | files, the file without module options don't need them. | |
755 | </para> | |
756 | ||
757 | <para> | |
758 | In addition to them, you'll need | |
759 | <filename><linux/interrupt.h></filename> for the interrupt | |
760 | handling, and <filename><asm/io.h></filename> for the i/o | |
761 | access. If you use <function>mdelay()</function> or | |
762 | <function>udelay()</function> functions, you'll need to include | |
763 | <filename><linux/delay.h></filename>, too. | |
764 | </para> | |
765 | ||
766 | <para> | |
767 | The ALSA interfaces like PCM or control API are defined in other | |
768 | header files as <filename><sound/xxx.h></filename>. | |
769 | They have to be included after | |
770 | <filename><sound/core.h></filename>. | |
771 | </para> | |
772 | ||
773 | </section> | |
774 | </chapter> | |
775 | ||
776 | ||
777 | <!-- ****************************************************** --> | |
778 | <!-- Management of Cards and Components --> | |
779 | <!-- ****************************************************** --> | |
780 | <chapter id="card-management"> | |
781 | <title>Management of Cards and Components</title> | |
782 | ||
783 | <section id="card-management-card-instance"> | |
784 | <title>Card Instance</title> | |
785 | <para> | |
786 | For each soundcard, a <quote>card</quote> record must be allocated. | |
787 | </para> | |
788 | ||
789 | <para> | |
790 | A card record is the headquarters of the soundcard. It manages | |
791 | the list of whole devices (components) on the soundcard, such as | |
792 | PCM, mixers, MIDI, synthesizer, and so on. Also, the card | |
793 | record holds the ID and the name strings of the card, manages | |
794 | the root of proc files, and controls the power-management states | |
795 | and hotplug disconnections. The component list on the card | |
796 | record is used to manage the proper releases of resources at | |
797 | destruction. | |
798 | </para> | |
799 | ||
800 | <para> | |
801 | As mentioned above, to create a card instance, call | |
802 | <function>snd_card_new()</function>. | |
803 | ||
804 | <informalexample> | |
805 | <programlisting> | |
806 | <![CDATA[ | |
446ab5f5 | 807 | struct snd_card *card; |
1da177e4 LT |
808 | card = snd_card_new(index, id, module, extra_size); |
809 | ]]> | |
810 | </programlisting> | |
811 | </informalexample> | |
812 | </para> | |
813 | ||
814 | <para> | |
815 | The function takes four arguments, the card-index number, the | |
816 | id string, the module pointer (usually | |
817 | <constant>THIS_MODULE</constant>), | |
818 | and the size of extra-data space. The last argument is used to | |
819 | allocate card->private_data for the | |
820 | chip-specific data. Note that this data | |
821 | <emphasis>is</emphasis> allocated by | |
822 | <function>snd_card_new()</function>. | |
823 | </para> | |
824 | </section> | |
825 | ||
826 | <section id="card-management-component"> | |
827 | <title>Components</title> | |
828 | <para> | |
829 | After the card is created, you can attach the components | |
830 | (devices) to the card instance. On ALSA driver, a component is | |
446ab5f5 | 831 | represented as a struct <structname>snd_device</structname> object. |
1da177e4 LT |
832 | A component can be a PCM instance, a control interface, a raw |
833 | MIDI interface, etc. Each of such instances has one component | |
834 | entry. | |
835 | </para> | |
836 | ||
837 | <para> | |
838 | A component can be created via | |
839 | <function>snd_device_new()</function> function. | |
840 | ||
841 | <informalexample> | |
842 | <programlisting> | |
843 | <![CDATA[ | |
844 | snd_device_new(card, SNDRV_DEV_XXX, chip, &ops); | |
845 | ]]> | |
846 | </programlisting> | |
847 | </informalexample> | |
848 | </para> | |
849 | ||
850 | <para> | |
851 | This takes the card pointer, the device-level | |
852 | (<constant>SNDRV_DEV_XXX</constant>), the data pointer, and the | |
853 | callback pointers (<parameter>&ops</parameter>). The | |
854 | device-level defines the type of components and the order of | |
855 | registration and de-registration. For most of components, the | |
856 | device-level is already defined. For a user-defined component, | |
857 | you can use <constant>SNDRV_DEV_LOWLEVEL</constant>. | |
858 | </para> | |
859 | ||
860 | <para> | |
861 | This function itself doesn't allocate the data space. The data | |
862 | must be allocated manually beforehand, and its pointer is passed | |
863 | as the argument. This pointer is used as the identifier | |
864 | (<parameter>chip</parameter> in the above example) for the | |
865 | instance. | |
866 | </para> | |
867 | ||
868 | <para> | |
869 | Each ALSA pre-defined component such as ac97 or pcm calls | |
870 | <function>snd_device_new()</function> inside its | |
871 | constructor. The destructor for each component is defined in the | |
872 | callback pointers. Hence, you don't need to take care of | |
873 | calling a destructor for such a component. | |
874 | </para> | |
875 | ||
876 | <para> | |
877 | If you would like to create your own component, you need to | |
878 | set the destructor function to dev_free callback in | |
879 | <parameter>ops</parameter>, so that it can be released | |
880 | automatically via <function>snd_card_free()</function>. The | |
881 | example will be shown later as an implementation of a | |
882 | chip-specific data. | |
883 | </para> | |
884 | </section> | |
885 | ||
886 | <section id="card-management-chip-specific"> | |
887 | <title>Chip-Specific Data</title> | |
888 | <para> | |
889 | The chip-specific information, e.g. the i/o port address, its | |
890 | resource pointer, or the irq number, is stored in the | |
891 | chip-specific record. | |
1da177e4 LT |
892 | |
893 | <informalexample> | |
894 | <programlisting> | |
895 | <![CDATA[ | |
446ab5f5 | 896 | struct mychip { |
1da177e4 LT |
897 | .... |
898 | }; | |
899 | ]]> | |
900 | </programlisting> | |
901 | </informalexample> | |
902 | </para> | |
903 | ||
904 | <para> | |
905 | In general, there are two ways to allocate the chip record. | |
906 | </para> | |
907 | ||
908 | <section id="card-management-chip-specific-snd-card-new"> | |
909 | <title>1. Allocating via <function>snd_card_new()</function>.</title> | |
910 | <para> | |
911 | As mentioned above, you can pass the extra-data-length to the 4th argument of <function>snd_card_new()</function>, i.e. | |
912 | ||
913 | <informalexample> | |
914 | <programlisting> | |
915 | <![CDATA[ | |
446ab5f5 | 916 | card = snd_card_new(index[dev], id[dev], THIS_MODULE, sizeof(struct mychip)); |
1da177e4 LT |
917 | ]]> |
918 | </programlisting> | |
919 | </informalexample> | |
920 | ||
446ab5f5 | 921 | whether struct <structname>mychip</structname> is the type of the chip record. |
1da177e4 LT |
922 | </para> |
923 | ||
924 | <para> | |
925 | In return, the allocated record can be accessed as | |
926 | ||
927 | <informalexample> | |
928 | <programlisting> | |
929 | <![CDATA[ | |
437a5a46 | 930 | struct mychip *chip = card->private_data; |
1da177e4 LT |
931 | ]]> |
932 | </programlisting> | |
933 | </informalexample> | |
934 | ||
935 | With this method, you don't have to allocate twice. | |
936 | The record is released together with the card instance. | |
937 | </para> | |
938 | </section> | |
939 | ||
940 | <section id="card-management-chip-specific-allocate-extra"> | |
941 | <title>2. Allocating an extra device.</title> | |
942 | ||
943 | <para> | |
944 | After allocating a card instance via | |
945 | <function>snd_card_new()</function> (with | |
946 | <constant>NULL</constant> on the 4th arg), call | |
561b220a | 947 | <function>kzalloc()</function>. |
1da177e4 LT |
948 | |
949 | <informalexample> | |
950 | <programlisting> | |
951 | <![CDATA[ | |
446ab5f5 TI |
952 | struct snd_card *card; |
953 | struct mychip *chip; | |
1da177e4 LT |
954 | card = snd_card_new(index[dev], id[dev], THIS_MODULE, NULL); |
955 | ..... | |
561b220a | 956 | chip = kzalloc(sizeof(*chip), GFP_KERNEL); |
1da177e4 LT |
957 | ]]> |
958 | </programlisting> | |
959 | </informalexample> | |
960 | </para> | |
961 | ||
962 | <para> | |
963 | The chip record should have the field to hold the card | |
964 | pointer at least, | |
965 | ||
966 | <informalexample> | |
967 | <programlisting> | |
968 | <![CDATA[ | |
446ab5f5 TI |
969 | struct mychip { |
970 | struct snd_card *card; | |
1da177e4 LT |
971 | .... |
972 | }; | |
973 | ]]> | |
974 | </programlisting> | |
975 | </informalexample> | |
976 | </para> | |
977 | ||
978 | <para> | |
979 | Then, set the card pointer in the returned chip instance. | |
980 | ||
981 | <informalexample> | |
982 | <programlisting> | |
983 | <![CDATA[ | |
984 | chip->card = card; | |
985 | ]]> | |
986 | </programlisting> | |
987 | </informalexample> | |
988 | </para> | |
989 | ||
990 | <para> | |
991 | Next, initialize the fields, and register this chip | |
992 | record as a low-level device with a specified | |
993 | <parameter>ops</parameter>, | |
994 | ||
995 | <informalexample> | |
996 | <programlisting> | |
997 | <![CDATA[ | |
446ab5f5 | 998 | static struct snd_device_ops ops = { |
1da177e4 LT |
999 | .dev_free = snd_mychip_dev_free, |
1000 | }; | |
1001 | .... | |
1002 | snd_device_new(card, SNDRV_DEV_LOWLEVEL, chip, &ops); | |
1003 | ]]> | |
1004 | </programlisting> | |
1005 | </informalexample> | |
1006 | ||
1007 | <function>snd_mychip_dev_free()</function> is the | |
1008 | device-destructor function, which will call the real | |
1009 | destructor. | |
1010 | </para> | |
1011 | ||
1012 | <para> | |
1013 | <informalexample> | |
1014 | <programlisting> | |
1015 | <![CDATA[ | |
446ab5f5 | 1016 | static int snd_mychip_dev_free(struct snd_device *device) |
1da177e4 | 1017 | { |
446ab5f5 | 1018 | return snd_mychip_free(device->device_data); |
1da177e4 LT |
1019 | } |
1020 | ]]> | |
1021 | </programlisting> | |
1022 | </informalexample> | |
1023 | ||
1024 | where <function>snd_mychip_free()</function> is the real destructor. | |
1025 | </para> | |
1026 | </section> | |
1027 | </section> | |
1028 | ||
1029 | <section id="card-management-registration"> | |
1030 | <title>Registration and Release</title> | |
1031 | <para> | |
1032 | After all components are assigned, register the card instance | |
1033 | by calling <function>snd_card_register()</function>. The access | |
1034 | to the device files are enabled at this point. That is, before | |
1035 | <function>snd_card_register()</function> is called, the | |
1036 | components are safely inaccessible from external side. If this | |
1037 | call fails, exit the probe function after releasing the card via | |
1038 | <function>snd_card_free()</function>. | |
1039 | </para> | |
1040 | ||
1041 | <para> | |
1042 | For releasing the card instance, you can call simply | |
1043 | <function>snd_card_free()</function>. As already mentioned, all | |
1044 | components are released automatically by this call. | |
1045 | </para> | |
1046 | ||
1047 | <para> | |
1048 | As further notes, the destructors (both | |
1049 | <function>snd_mychip_dev_free</function> and | |
1050 | <function>snd_mychip_free</function>) cannot be defined with | |
1051 | <parameter>__devexit</parameter> prefix, because they may be | |
1052 | called from the constructor, too, at the false path. | |
1053 | </para> | |
1054 | ||
1055 | <para> | |
1056 | For a device which allows hotplugging, you can use | |
2b29b13c TI |
1057 | <function>snd_card_free_when_closed</function>. This one will |
1058 | postpone the destruction until all devices are closed. | |
1da177e4 LT |
1059 | </para> |
1060 | ||
1061 | </section> | |
1062 | ||
1063 | </chapter> | |
1064 | ||
1065 | ||
1066 | <!-- ****************************************************** --> | |
1067 | <!-- PCI Resource Managements --> | |
1068 | <!-- ****************************************************** --> | |
1069 | <chapter id="pci-resource"> | |
1070 | <title>PCI Resource Managements</title> | |
1071 | ||
1072 | <section id="pci-resource-example"> | |
1073 | <title>Full Code Example</title> | |
1074 | <para> | |
1075 | In this section, we'll finish the chip-specific constructor, | |
1076 | destructor and PCI entries. The example code is shown first, | |
1077 | below. | |
1078 | ||
1079 | <example> | |
1080 | <title>PCI Resource Managements Example</title> | |
1081 | <programlisting> | |
1082 | <![CDATA[ | |
446ab5f5 TI |
1083 | struct mychip { |
1084 | struct snd_card *card; | |
1da177e4 LT |
1085 | struct pci_dev *pci; |
1086 | ||
1087 | unsigned long port; | |
1088 | int irq; | |
1089 | }; | |
1090 | ||
446ab5f5 | 1091 | static int snd_mychip_free(struct mychip *chip) |
1da177e4 LT |
1092 | { |
1093 | /* disable hardware here if any */ | |
1094 | .... // (not implemented in this document) | |
1095 | ||
1096 | /* release the irq */ | |
1097 | if (chip->irq >= 0) | |
437a5a46 | 1098 | free_irq(chip->irq, chip); |
1da177e4 LT |
1099 | /* release the i/o ports & memory */ |
1100 | pci_release_regions(chip->pci); | |
1101 | /* disable the PCI entry */ | |
1102 | pci_disable_device(chip->pci); | |
1103 | /* release the data */ | |
1104 | kfree(chip); | |
1105 | return 0; | |
1106 | } | |
1107 | ||
1108 | /* chip-specific constructor */ | |
446ab5f5 | 1109 | static int __devinit snd_mychip_create(struct snd_card *card, |
1da177e4 | 1110 | struct pci_dev *pci, |
446ab5f5 | 1111 | struct mychip **rchip) |
1da177e4 | 1112 | { |
446ab5f5 | 1113 | struct mychip *chip; |
1da177e4 | 1114 | int err; |
446ab5f5 | 1115 | static struct snd_device_ops ops = { |
1da177e4 LT |
1116 | .dev_free = snd_mychip_dev_free, |
1117 | }; | |
1118 | ||
1119 | *rchip = NULL; | |
1120 | ||
1121 | /* initialize the PCI entry */ | |
1122 | if ((err = pci_enable_device(pci)) < 0) | |
1123 | return err; | |
1124 | /* check PCI availability (28bit DMA) */ | |
56b146d3 TK |
1125 | if (pci_set_dma_mask(pci, DMA_28BIT_MASK) < 0 || |
1126 | pci_set_consistent_dma_mask(pci, DMA_28BIT_MASK) < 0) { | |
1da177e4 LT |
1127 | printk(KERN_ERR "error to set 28bit mask DMA\n"); |
1128 | pci_disable_device(pci); | |
1129 | return -ENXIO; | |
1130 | } | |
1131 | ||
561b220a | 1132 | chip = kzalloc(sizeof(*chip), GFP_KERNEL); |
1da177e4 LT |
1133 | if (chip == NULL) { |
1134 | pci_disable_device(pci); | |
1135 | return -ENOMEM; | |
1136 | } | |
1137 | ||
1138 | /* initialize the stuff */ | |
1139 | chip->card = card; | |
1140 | chip->pci = pci; | |
1141 | chip->irq = -1; | |
1142 | ||
1143 | /* (1) PCI resource allocation */ | |
1144 | if ((err = pci_request_regions(pci, "My Chip")) < 0) { | |
1145 | kfree(chip); | |
1146 | pci_disable_device(pci); | |
1147 | return err; | |
1148 | } | |
1149 | chip->port = pci_resource_start(pci, 0); | |
1150 | if (request_irq(pci->irq, snd_mychip_interrupt, | |
437a5a46 | 1151 | IRQF_SHARED, "My Chip", chip)) { |
1da177e4 LT |
1152 | printk(KERN_ERR "cannot grab irq %d\n", pci->irq); |
1153 | snd_mychip_free(chip); | |
1154 | return -EBUSY; | |
1155 | } | |
1156 | chip->irq = pci->irq; | |
1157 | ||
1158 | /* (2) initialization of the chip hardware */ | |
1159 | .... // (not implemented in this document) | |
1160 | ||
1161 | if ((err = snd_device_new(card, SNDRV_DEV_LOWLEVEL, | |
1162 | chip, &ops)) < 0) { | |
1163 | snd_mychip_free(chip); | |
1164 | return err; | |
1165 | } | |
1166 | ||
1167 | snd_card_set_dev(card, &pci->dev); | |
1168 | ||
1169 | *rchip = chip; | |
1170 | return 0; | |
1171 | } | |
1172 | ||
1173 | /* PCI IDs */ | |
f40b6890 | 1174 | static struct pci_device_id snd_mychip_ids[] = { |
1da177e4 LT |
1175 | { PCI_VENDOR_ID_FOO, PCI_DEVICE_ID_BAR, |
1176 | PCI_ANY_ID, PCI_ANY_ID, 0, 0, 0, }, | |
1177 | .... | |
1178 | { 0, } | |
1179 | }; | |
1180 | MODULE_DEVICE_TABLE(pci, snd_mychip_ids); | |
1181 | ||
1182 | /* pci_driver definition */ | |
1183 | static struct pci_driver driver = { | |
1184 | .name = "My Own Chip", | |
1185 | .id_table = snd_mychip_ids, | |
1186 | .probe = snd_mychip_probe, | |
1187 | .remove = __devexit_p(snd_mychip_remove), | |
1188 | }; | |
1189 | ||
1190 | /* initialization of the module */ | |
1191 | static int __init alsa_card_mychip_init(void) | |
1192 | { | |
01d25d46 | 1193 | return pci_register_driver(&driver); |
1da177e4 LT |
1194 | } |
1195 | ||
1196 | /* clean up the module */ | |
1197 | static void __exit alsa_card_mychip_exit(void) | |
1198 | { | |
1199 | pci_unregister_driver(&driver); | |
1200 | } | |
1201 | ||
1202 | module_init(alsa_card_mychip_init) | |
1203 | module_exit(alsa_card_mychip_exit) | |
1204 | ||
1205 | EXPORT_NO_SYMBOLS; /* for old kernels only */ | |
1206 | ]]> | |
1207 | </programlisting> | |
1208 | </example> | |
1209 | </para> | |
1210 | </section> | |
1211 | ||
1212 | <section id="pci-resource-some-haftas"> | |
1213 | <title>Some Hafta's</title> | |
1214 | <para> | |
1215 | The allocation of PCI resources is done in the | |
1216 | <function>probe()</function> function, and usually an extra | |
1217 | <function>xxx_create()</function> function is written for this | |
56b146d3 | 1218 | purpose. |
1da177e4 LT |
1219 | </para> |
1220 | ||
1221 | <para> | |
1222 | In the case of PCI devices, you have to call at first | |
1223 | <function>pci_enable_device()</function> function before | |
1224 | allocating resources. Also, you need to set the proper PCI DMA | |
1225 | mask to limit the accessed i/o range. In some cases, you might | |
1226 | need to call <function>pci_set_master()</function> function, | |
56b146d3 | 1227 | too. |
1da177e4 LT |
1228 | </para> |
1229 | ||
1230 | <para> | |
1231 | Suppose the 28bit mask, and the code to be added would be like: | |
1232 | ||
1233 | <informalexample> | |
1234 | <programlisting> | |
1235 | <![CDATA[ | |
1236 | if ((err = pci_enable_device(pci)) < 0) | |
1237 | return err; | |
56b146d3 TK |
1238 | if (pci_set_dma_mask(pci, DMA_28BIT_MASK) < 0 || |
1239 | pci_set_consistent_dma_mask(pci, DMA_28BIT_MASK) < 0) { | |
1da177e4 LT |
1240 | printk(KERN_ERR "error to set 28bit mask DMA\n"); |
1241 | pci_disable_device(pci); | |
1242 | return -ENXIO; | |
1243 | } | |
1244 | ||
1245 | ]]> | |
1246 | </programlisting> | |
1247 | </informalexample> | |
1248 | </para> | |
1249 | </section> | |
1250 | ||
1251 | <section id="pci-resource-resource-allocation"> | |
1252 | <title>Resource Allocation</title> | |
1253 | <para> | |
1254 | The allocation of I/O ports and irqs are done via standard kernel | |
1255 | functions. Unlike ALSA ver.0.5.x., there are no helpers for | |
1256 | that. And these resources must be released in the destructor | |
1257 | function (see below). Also, on ALSA 0.9.x, you don't need to | |
56b146d3 | 1258 | allocate (pseudo-)DMA for PCI like ALSA 0.5.x. |
1da177e4 LT |
1259 | </para> |
1260 | ||
1261 | <para> | |
1262 | Now assume that this PCI device has an I/O port with 8 bytes | |
446ab5f5 | 1263 | and an interrupt. Then struct <structname>mychip</structname> will have the |
56b146d3 | 1264 | following fields: |
1da177e4 LT |
1265 | |
1266 | <informalexample> | |
1267 | <programlisting> | |
1268 | <![CDATA[ | |
446ab5f5 TI |
1269 | struct mychip { |
1270 | struct snd_card *card; | |
1da177e4 LT |
1271 | |
1272 | unsigned long port; | |
1273 | int irq; | |
1274 | }; | |
1275 | ]]> | |
1276 | </programlisting> | |
1277 | </informalexample> | |
1278 | </para> | |
1279 | ||
1280 | <para> | |
1281 | For an i/o port (and also a memory region), you need to have | |
1282 | the resource pointer for the standard resource management. For | |
1283 | an irq, you have to keep only the irq number (integer). But you | |
1284 | need to initialize this number as -1 before actual allocation, | |
1285 | since irq 0 is valid. The port address and its resource pointer | |
1286 | can be initialized as null by | |
561b220a | 1287 | <function>kzalloc()</function> automatically, so you |
1da177e4 LT |
1288 | don't have to take care of resetting them. |
1289 | </para> | |
1290 | ||
1291 | <para> | |
1292 | The allocation of an i/o port is done like this: | |
1293 | ||
1294 | <informalexample> | |
1295 | <programlisting> | |
1296 | <![CDATA[ | |
1297 | if ((err = pci_request_regions(pci, "My Chip")) < 0) { | |
1298 | kfree(chip); | |
1299 | pci_disable_device(pci); | |
1300 | return err; | |
1301 | } | |
1302 | chip->port = pci_resource_start(pci, 0); | |
1303 | ]]> | |
1304 | </programlisting> | |
1305 | </informalexample> | |
1306 | </para> | |
1307 | ||
1308 | <para> | |
1309 | <!-- obsolete --> | |
1310 | It will reserve the i/o port region of 8 bytes of the given | |
1311 | PCI device. The returned value, chip->res_port, is allocated | |
1312 | via <function>kmalloc()</function> by | |
1313 | <function>request_region()</function>. The pointer must be | |
1314 | released via <function>kfree()</function>, but there is some | |
1315 | problem regarding this. This issue will be explained more below. | |
1316 | </para> | |
1317 | ||
1318 | <para> | |
1319 | The allocation of an interrupt source is done like this: | |
1320 | ||
1321 | <informalexample> | |
1322 | <programlisting> | |
1323 | <![CDATA[ | |
1324 | if (request_irq(pci->irq, snd_mychip_interrupt, | |
6ce6c7fa | 1325 | IRQF_DISABLED|IRQF_SHARED, "My Chip", chip)) { |
1da177e4 LT |
1326 | printk(KERN_ERR "cannot grab irq %d\n", pci->irq); |
1327 | snd_mychip_free(chip); | |
1328 | return -EBUSY; | |
1329 | } | |
1330 | chip->irq = pci->irq; | |
1331 | ]]> | |
1332 | </programlisting> | |
1333 | </informalexample> | |
1334 | ||
1335 | where <function>snd_mychip_interrupt()</function> is the | |
1336 | interrupt handler defined <link | |
1337 | linkend="pcm-interface-interrupt-handler"><citetitle>later</citetitle></link>. | |
1338 | Note that chip->irq should be defined | |
1339 | only when <function>request_irq()</function> succeeded. | |
1340 | </para> | |
1341 | ||
1342 | <para> | |
1343 | On the PCI bus, the interrupts can be shared. Thus, | |
6ce6c7fa | 1344 | <constant>IRQF_SHARED</constant> is given as the interrupt flag of |
1da177e4 LT |
1345 | <function>request_irq()</function>. |
1346 | </para> | |
1347 | ||
1348 | <para> | |
1349 | The last argument of <function>request_irq()</function> is the | |
1350 | data pointer passed to the interrupt handler. Usually, the | |
1351 | chip-specific record is used for that, but you can use what you | |
1352 | like, too. | |
1353 | </para> | |
1354 | ||
1355 | <para> | |
1356 | I won't define the detail of the interrupt handler at this | |
1357 | point, but at least its appearance can be explained now. The | |
1358 | interrupt handler looks usually like the following: | |
1359 | ||
1360 | <informalexample> | |
1361 | <programlisting> | |
1362 | <![CDATA[ | |
1363 | static irqreturn_t snd_mychip_interrupt(int irq, void *dev_id, | |
1364 | struct pt_regs *regs) | |
1365 | { | |
446ab5f5 | 1366 | struct mychip *chip = dev_id; |
1da177e4 LT |
1367 | .... |
1368 | return IRQ_HANDLED; | |
1369 | } | |
1370 | ]]> | |
1371 | </programlisting> | |
1372 | </informalexample> | |
1373 | </para> | |
1374 | ||
1375 | <para> | |
1376 | Now let's write the corresponding destructor for the resources | |
1377 | above. The role of destructor is simple: disable the hardware | |
1378 | (if already activated) and release the resources. So far, we | |
1379 | have no hardware part, so the disabling is not written here. | |
1380 | </para> | |
1381 | ||
1382 | <para> | |
1383 | For releasing the resources, <quote>check-and-release</quote> | |
1384 | method is a safer way. For the interrupt, do like this: | |
1385 | ||
1386 | <informalexample> | |
1387 | <programlisting> | |
1388 | <![CDATA[ | |
1389 | if (chip->irq >= 0) | |
437a5a46 | 1390 | free_irq(chip->irq, chip); |
1da177e4 LT |
1391 | ]]> |
1392 | </programlisting> | |
1393 | </informalexample> | |
1394 | ||
1395 | Since the irq number can start from 0, you should initialize | |
1396 | chip->irq with a negative value (e.g. -1), so that you can | |
1397 | check the validity of the irq number as above. | |
1398 | </para> | |
1399 | ||
1400 | <para> | |
1401 | When you requested I/O ports or memory regions via | |
1402 | <function>pci_request_region()</function> or | |
1403 | <function>pci_request_regions()</function> like this example, | |
1404 | release the resource(s) using the corresponding function, | |
1405 | <function>pci_release_region()</function> or | |
1406 | <function>pci_release_regions()</function>. | |
1407 | ||
1408 | <informalexample> | |
1409 | <programlisting> | |
1410 | <![CDATA[ | |
1411 | pci_release_regions(chip->pci); | |
1412 | ]]> | |
1413 | </programlisting> | |
1414 | </informalexample> | |
1415 | </para> | |
1416 | ||
1417 | <para> | |
1418 | When you requested manually via <function>request_region()</function> | |
1419 | or <function>request_mem_region</function>, you can release it via | |
1420 | <function>release_resource()</function>. Suppose that you keep | |
1421 | the resource pointer returned from <function>request_region()</function> | |
1422 | in chip->res_port, the release procedure looks like below: | |
1423 | ||
1424 | <informalexample> | |
1425 | <programlisting> | |
1426 | <![CDATA[ | |
b1d5776d | 1427 | release_and_free_resource(chip->res_port); |
1da177e4 LT |
1428 | ]]> |
1429 | </programlisting> | |
1430 | </informalexample> | |
1da177e4 LT |
1431 | </para> |
1432 | ||
1433 | <para> | |
1434 | Don't forget to call <function>pci_disable_device()</function> | |
1435 | before all finished. | |
1436 | </para> | |
1437 | ||
1438 | <para> | |
1439 | And finally, release the chip-specific record. | |
1440 | ||
1441 | <informalexample> | |
1442 | <programlisting> | |
1443 | <![CDATA[ | |
1444 | kfree(chip); | |
1445 | ]]> | |
1446 | </programlisting> | |
1447 | </informalexample> | |
1448 | </para> | |
1449 | ||
1450 | <para> | |
1451 | Again, remember that you cannot | |
1452 | set <parameter>__devexit</parameter> prefix for this destructor. | |
1453 | </para> | |
1454 | ||
1455 | <para> | |
1456 | We didn't implement the hardware-disabling part in the above. | |
1457 | If you need to do this, please note that the destructor may be | |
1458 | called even before the initialization of the chip is completed. | |
1459 | It would be better to have a flag to skip the hardware-disabling | |
1460 | if the hardware was not initialized yet. | |
1461 | </para> | |
1462 | ||
1463 | <para> | |
1464 | When the chip-data is assigned to the card using | |
1465 | <function>snd_device_new()</function> with | |
1466 | <constant>SNDRV_DEV_LOWLELVEL</constant> , its destructor is | |
1467 | called at the last. That is, it is assured that all other | |
1468 | components like PCMs and controls have been already released. | |
1469 | You don't have to call stopping PCMs, etc. explicitly, but just | |
1470 | stop the hardware in the low-level. | |
1471 | </para> | |
1472 | ||
1473 | <para> | |
1474 | The management of a memory-mapped region is almost as same as | |
1475 | the management of an i/o port. You'll need three fields like | |
1476 | the following: | |
1477 | ||
1478 | <informalexample> | |
1479 | <programlisting> | |
1480 | <![CDATA[ | |
446ab5f5 | 1481 | struct mychip { |
1da177e4 LT |
1482 | .... |
1483 | unsigned long iobase_phys; | |
1484 | void __iomem *iobase_virt; | |
1485 | }; | |
1486 | ]]> | |
1487 | </programlisting> | |
1488 | </informalexample> | |
1489 | ||
1490 | and the allocation would be like below: | |
1491 | ||
1492 | <informalexample> | |
1493 | <programlisting> | |
1494 | <![CDATA[ | |
1495 | if ((err = pci_request_regions(pci, "My Chip")) < 0) { | |
1496 | kfree(chip); | |
1497 | return err; | |
1498 | } | |
1499 | chip->iobase_phys = pci_resource_start(pci, 0); | |
1500 | chip->iobase_virt = ioremap_nocache(chip->iobase_phys, | |
1501 | pci_resource_len(pci, 0)); | |
1502 | ]]> | |
1503 | </programlisting> | |
1504 | </informalexample> | |
1505 | ||
1506 | and the corresponding destructor would be: | |
1507 | ||
1508 | <informalexample> | |
1509 | <programlisting> | |
1510 | <![CDATA[ | |
446ab5f5 | 1511 | static int snd_mychip_free(struct mychip *chip) |
1da177e4 LT |
1512 | { |
1513 | .... | |
1514 | if (chip->iobase_virt) | |
1515 | iounmap(chip->iobase_virt); | |
1516 | .... | |
1517 | pci_release_regions(chip->pci); | |
1518 | .... | |
1519 | } | |
1520 | ]]> | |
1521 | </programlisting> | |
1522 | </informalexample> | |
1523 | </para> | |
1524 | ||
1525 | </section> | |
1526 | ||
1527 | <section id="pci-resource-device-struct"> | |
1528 | <title>Registration of Device Struct</title> | |
1529 | <para> | |
1530 | At some point, typically after calling <function>snd_device_new()</function>, | |
446ab5f5 | 1531 | you need to register the struct <structname>device</structname> of the chip |
1da177e4 LT |
1532 | you're handling for udev and co. ALSA provides a macro for compatibility with |
1533 | older kernels. Simply call like the following: | |
1534 | <informalexample> | |
1535 | <programlisting> | |
1536 | <![CDATA[ | |
1537 | snd_card_set_dev(card, &pci->dev); | |
1538 | ]]> | |
1539 | </programlisting> | |
1540 | </informalexample> | |
1541 | so that it stores the PCI's device pointer to the card. This will be | |
1542 | referred by ALSA core functions later when the devices are registered. | |
1543 | </para> | |
1544 | <para> | |
1545 | In the case of non-PCI, pass the proper device struct pointer of the BUS | |
1546 | instead. (In the case of legacy ISA without PnP, you don't have to do | |
1547 | anything.) | |
1548 | </para> | |
1549 | </section> | |
1550 | ||
1551 | <section id="pci-resource-entries"> | |
1552 | <title>PCI Entries</title> | |
1553 | <para> | |
1554 | So far, so good. Let's finish the rest of missing PCI | |
1555 | stuffs. At first, we need a | |
1556 | <structname>pci_device_id</structname> table for this | |
1557 | chipset. It's a table of PCI vendor/device ID number, and some | |
1558 | masks. | |
1559 | </para> | |
1560 | ||
1561 | <para> | |
1562 | For example, | |
1563 | ||
1564 | <informalexample> | |
1565 | <programlisting> | |
1566 | <![CDATA[ | |
f40b6890 | 1567 | static struct pci_device_id snd_mychip_ids[] = { |
1da177e4 LT |
1568 | { PCI_VENDOR_ID_FOO, PCI_DEVICE_ID_BAR, |
1569 | PCI_ANY_ID, PCI_ANY_ID, 0, 0, 0, }, | |
1570 | .... | |
1571 | { 0, } | |
1572 | }; | |
1573 | MODULE_DEVICE_TABLE(pci, snd_mychip_ids); | |
1574 | ]]> | |
1575 | </programlisting> | |
1576 | </informalexample> | |
1577 | </para> | |
1578 | ||
1579 | <para> | |
1580 | The first and second fields of | |
1581 | <structname>pci_device_id</structname> struct are the vendor and | |
1582 | device IDs. If you have nothing special to filter the matching | |
1583 | devices, you can use the rest of fields like above. The last | |
1584 | field of <structname>pci_device_id</structname> struct is a | |
1585 | private data for this entry. You can specify any value here, for | |
1586 | example, to tell the type of different operations per each | |
1587 | device IDs. Such an example is found in intel8x0 driver. | |
1588 | </para> | |
1589 | ||
1590 | <para> | |
1591 | The last entry of this list is the terminator. You must | |
1592 | specify this all-zero entry. | |
1593 | </para> | |
1594 | ||
1595 | <para> | |
1596 | Then, prepare the <structname>pci_driver</structname> record: | |
1597 | ||
1598 | <informalexample> | |
1599 | <programlisting> | |
1600 | <![CDATA[ | |
1601 | static struct pci_driver driver = { | |
1602 | .name = "My Own Chip", | |
1603 | .id_table = snd_mychip_ids, | |
1604 | .probe = snd_mychip_probe, | |
1605 | .remove = __devexit_p(snd_mychip_remove), | |
1606 | }; | |
1607 | ]]> | |
1608 | </programlisting> | |
1609 | </informalexample> | |
1610 | </para> | |
1611 | ||
1612 | <para> | |
1613 | The <structfield>probe</structfield> and | |
1614 | <structfield>remove</structfield> functions are what we already | |
1615 | defined in | |
1616 | the previous sections. The <structfield>remove</structfield> should | |
1617 | be defined with | |
1618 | <function>__devexit_p()</function> macro, so that it's not | |
1619 | defined for built-in (and non-hot-pluggable) case. The | |
1620 | <structfield>name</structfield> | |
1621 | field is the name string of this device. Note that you must not | |
1622 | use a slash <quote>/</quote> in this string. | |
1623 | </para> | |
1624 | ||
1625 | <para> | |
1626 | And at last, the module entries: | |
1627 | ||
1628 | <informalexample> | |
1629 | <programlisting> | |
1630 | <![CDATA[ | |
1631 | static int __init alsa_card_mychip_init(void) | |
1632 | { | |
01d25d46 | 1633 | return pci_register_driver(&driver); |
1da177e4 LT |
1634 | } |
1635 | ||
1636 | static void __exit alsa_card_mychip_exit(void) | |
1637 | { | |
1638 | pci_unregister_driver(&driver); | |
1639 | } | |
1640 | ||
1641 | module_init(alsa_card_mychip_init) | |
1642 | module_exit(alsa_card_mychip_exit) | |
1643 | ]]> | |
1644 | </programlisting> | |
1645 | </informalexample> | |
1646 | </para> | |
1647 | ||
1648 | <para> | |
1649 | Note that these module entries are tagged with | |
1650 | <parameter>__init</parameter> and | |
1651 | <parameter>__exit</parameter> prefixes, not | |
1652 | <parameter>__devinit</parameter> nor | |
1653 | <parameter>__devexit</parameter>. | |
1654 | </para> | |
1655 | ||
1656 | <para> | |
1657 | Oh, one thing was forgotten. If you have no exported symbols, | |
1658 | you need to declare it on 2.2 or 2.4 kernels (on 2.6 kernels | |
1659 | it's not necessary, though). | |
1660 | ||
1661 | <informalexample> | |
1662 | <programlisting> | |
1663 | <![CDATA[ | |
1664 | EXPORT_NO_SYMBOLS; | |
1665 | ]]> | |
1666 | </programlisting> | |
1667 | </informalexample> | |
1668 | ||
1669 | That's all! | |
1670 | </para> | |
1671 | </section> | |
1672 | </chapter> | |
1673 | ||
1674 | ||
1675 | <!-- ****************************************************** --> | |
1676 | <!-- PCM Interface --> | |
1677 | <!-- ****************************************************** --> | |
1678 | <chapter id="pcm-interface"> | |
1679 | <title>PCM Interface</title> | |
1680 | ||
1681 | <section id="pcm-interface-general"> | |
1682 | <title>General</title> | |
1683 | <para> | |
1684 | The PCM middle layer of ALSA is quite powerful and it is only | |
1685 | necessary for each driver to implement the low-level functions | |
1686 | to access its hardware. | |
1687 | </para> | |
1688 | ||
1689 | <para> | |
1690 | For accessing to the PCM layer, you need to include | |
1691 | <filename><sound/pcm.h></filename> above all. In addition, | |
1692 | <filename><sound/pcm_params.h></filename> might be needed | |
1693 | if you access to some functions related with hw_param. | |
1694 | </para> | |
1695 | ||
1696 | <para> | |
1697 | Each card device can have up to four pcm instances. A pcm | |
1698 | instance corresponds to a pcm device file. The limitation of | |
1699 | number of instances comes only from the available bit size of | |
1700 | the linux's device number. Once when 64bit device number is | |
1701 | used, we'll have more available pcm instances. | |
1702 | </para> | |
1703 | ||
1704 | <para> | |
1705 | A pcm instance consists of pcm playback and capture streams, | |
1706 | and each pcm stream consists of one or more pcm substreams. Some | |
1707 | soundcard supports the multiple-playback function. For example, | |
1708 | emu10k1 has a PCM playback of 32 stereo substreams. In this case, at | |
1709 | each open, a free substream is (usually) automatically chosen | |
1710 | and opened. Meanwhile, when only one substream exists and it was | |
1711 | already opened, the succeeding open will result in the blocking | |
1712 | or the error with <constant>EAGAIN</constant> according to the | |
1713 | file open mode. But you don't have to know the detail in your | |
1714 | driver. The PCM middle layer will take all such jobs. | |
1715 | </para> | |
1716 | </section> | |
1717 | ||
1718 | <section id="pcm-interface-example"> | |
1719 | <title>Full Code Example</title> | |
1720 | <para> | |
1721 | The example code below does not include any hardware access | |
1722 | routines but shows only the skeleton, how to build up the PCM | |
1723 | interfaces. | |
1724 | ||
1725 | <example> | |
1726 | <title>PCM Example Code</title> | |
1727 | <programlisting> | |
1728 | <![CDATA[ | |
1729 | #include <sound/pcm.h> | |
1730 | .... | |
1731 | ||
1732 | /* hardware definition */ | |
446ab5f5 | 1733 | static struct snd_pcm_hardware snd_mychip_playback_hw = { |
1da177e4 LT |
1734 | .info = (SNDRV_PCM_INFO_MMAP | |
1735 | SNDRV_PCM_INFO_INTERLEAVED | | |
1736 | SNDRV_PCM_INFO_BLOCK_TRANSFER | | |
1737 | SNDRV_PCM_INFO_MMAP_VALID), | |
1738 | .formats = SNDRV_PCM_FMTBIT_S16_LE, | |
1739 | .rates = SNDRV_PCM_RATE_8000_48000, | |
1740 | .rate_min = 8000, | |
1741 | .rate_max = 48000, | |
1742 | .channels_min = 2, | |
1743 | .channels_max = 2, | |
1744 | .buffer_bytes_max = 32768, | |
1745 | .period_bytes_min = 4096, | |
1746 | .period_bytes_max = 32768, | |
1747 | .periods_min = 1, | |
1748 | .periods_max = 1024, | |
1749 | }; | |
1750 | ||
1751 | /* hardware definition */ | |
446ab5f5 | 1752 | static struct snd_pcm_hardware snd_mychip_capture_hw = { |
1da177e4 LT |
1753 | .info = (SNDRV_PCM_INFO_MMAP | |
1754 | SNDRV_PCM_INFO_INTERLEAVED | | |
1755 | SNDRV_PCM_INFO_BLOCK_TRANSFER | | |
1756 | SNDRV_PCM_INFO_MMAP_VALID), | |
1757 | .formats = SNDRV_PCM_FMTBIT_S16_LE, | |
1758 | .rates = SNDRV_PCM_RATE_8000_48000, | |
1759 | .rate_min = 8000, | |
1760 | .rate_max = 48000, | |
1761 | .channels_min = 2, | |
1762 | .channels_max = 2, | |
1763 | .buffer_bytes_max = 32768, | |
1764 | .period_bytes_min = 4096, | |
1765 | .period_bytes_max = 32768, | |
1766 | .periods_min = 1, | |
1767 | .periods_max = 1024, | |
1768 | }; | |
1769 | ||
1770 | /* open callback */ | |
446ab5f5 | 1771 | static int snd_mychip_playback_open(struct snd_pcm_substream *substream) |
1da177e4 | 1772 | { |
446ab5f5 TI |
1773 | struct mychip *chip = snd_pcm_substream_chip(substream); |
1774 | struct snd_pcm_runtime *runtime = substream->runtime; | |
1da177e4 LT |
1775 | |
1776 | runtime->hw = snd_mychip_playback_hw; | |
1777 | // more hardware-initialization will be done here | |
1778 | return 0; | |
1779 | } | |
1780 | ||
1781 | /* close callback */ | |
446ab5f5 | 1782 | static int snd_mychip_playback_close(struct snd_pcm_substream *substream) |
1da177e4 | 1783 | { |
446ab5f5 | 1784 | struct mychip *chip = snd_pcm_substream_chip(substream); |
1da177e4 LT |
1785 | // the hardware-specific codes will be here |
1786 | return 0; | |
1787 | ||
1788 | } | |
1789 | ||
1790 | /* open callback */ | |
446ab5f5 | 1791 | static int snd_mychip_capture_open(struct snd_pcm_substream *substream) |
1da177e4 | 1792 | { |
446ab5f5 TI |
1793 | struct mychip *chip = snd_pcm_substream_chip(substream); |
1794 | struct snd_pcm_runtime *runtime = substream->runtime; | |
1da177e4 LT |
1795 | |
1796 | runtime->hw = snd_mychip_capture_hw; | |
1797 | // more hardware-initialization will be done here | |
1798 | return 0; | |
1799 | } | |
1800 | ||
1801 | /* close callback */ | |
446ab5f5 | 1802 | static int snd_mychip_capture_close(struct snd_pcm_substream *substream) |
1da177e4 | 1803 | { |
446ab5f5 | 1804 | struct mychip *chip = snd_pcm_substream_chip(substream); |
1da177e4 LT |
1805 | // the hardware-specific codes will be here |
1806 | return 0; | |
1807 | ||
1808 | } | |
1809 | ||
1810 | /* hw_params callback */ | |
446ab5f5 TI |
1811 | static int snd_mychip_pcm_hw_params(struct snd_pcm_substream *substream, |
1812 | struct snd_pcm_hw_params *hw_params) | |
1da177e4 LT |
1813 | { |
1814 | return snd_pcm_lib_malloc_pages(substream, | |
1815 | params_buffer_bytes(hw_params)); | |
1816 | } | |
1817 | ||
1818 | /* hw_free callback */ | |
446ab5f5 | 1819 | static int snd_mychip_pcm_hw_free(struct snd_pcm_substream *substream) |
1da177e4 LT |
1820 | { |
1821 | return snd_pcm_lib_free_pages(substream); | |
1822 | } | |
1823 | ||
1824 | /* prepare callback */ | |
446ab5f5 | 1825 | static int snd_mychip_pcm_prepare(struct snd_pcm_substream *substream) |
1da177e4 | 1826 | { |
446ab5f5 TI |
1827 | struct mychip *chip = snd_pcm_substream_chip(substream); |
1828 | struct snd_pcm_runtime *runtime = substream->runtime; | |
1da177e4 LT |
1829 | |
1830 | /* set up the hardware with the current configuration | |
1831 | * for example... | |
1832 | */ | |
1833 | mychip_set_sample_format(chip, runtime->format); | |
1834 | mychip_set_sample_rate(chip, runtime->rate); | |
1835 | mychip_set_channels(chip, runtime->channels); | |
0b7bed4e | 1836 | mychip_set_dma_setup(chip, runtime->dma_addr, |
1da177e4 LT |
1837 | chip->buffer_size, |
1838 | chip->period_size); | |
1839 | return 0; | |
1840 | } | |
1841 | ||
1842 | /* trigger callback */ | |
446ab5f5 | 1843 | static int snd_mychip_pcm_trigger(struct snd_pcm_substream *substream, |
1da177e4 LT |
1844 | int cmd) |
1845 | { | |
1846 | switch (cmd) { | |
1847 | case SNDRV_PCM_TRIGGER_START: | |
1848 | // do something to start the PCM engine | |
1849 | break; | |
1850 | case SNDRV_PCM_TRIGGER_STOP: | |
1851 | // do something to stop the PCM engine | |
1852 | break; | |
1853 | default: | |
1854 | return -EINVAL; | |
1855 | } | |
1856 | } | |
1857 | ||
1858 | /* pointer callback */ | |
1859 | static snd_pcm_uframes_t | |
446ab5f5 | 1860 | snd_mychip_pcm_pointer(struct snd_pcm_substream *substream) |
1da177e4 | 1861 | { |
446ab5f5 | 1862 | struct mychip *chip = snd_pcm_substream_chip(substream); |
1da177e4 LT |
1863 | unsigned int current_ptr; |
1864 | ||
1865 | /* get the current hardware pointer */ | |
1866 | current_ptr = mychip_get_hw_pointer(chip); | |
1867 | return current_ptr; | |
1868 | } | |
1869 | ||
1870 | /* operators */ | |
446ab5f5 | 1871 | static struct snd_pcm_ops snd_mychip_playback_ops = { |
1da177e4 LT |
1872 | .open = snd_mychip_playback_open, |
1873 | .close = snd_mychip_playback_close, | |
1874 | .ioctl = snd_pcm_lib_ioctl, | |
1875 | .hw_params = snd_mychip_pcm_hw_params, | |
1876 | .hw_free = snd_mychip_pcm_hw_free, | |
1877 | .prepare = snd_mychip_pcm_prepare, | |
1878 | .trigger = snd_mychip_pcm_trigger, | |
1879 | .pointer = snd_mychip_pcm_pointer, | |
1880 | }; | |
1881 | ||
1882 | /* operators */ | |
446ab5f5 | 1883 | static struct snd_pcm_ops snd_mychip_capture_ops = { |
1da177e4 LT |
1884 | .open = snd_mychip_capture_open, |
1885 | .close = snd_mychip_capture_close, | |
1886 | .ioctl = snd_pcm_lib_ioctl, | |
1887 | .hw_params = snd_mychip_pcm_hw_params, | |
1888 | .hw_free = snd_mychip_pcm_hw_free, | |
1889 | .prepare = snd_mychip_pcm_prepare, | |
1890 | .trigger = snd_mychip_pcm_trigger, | |
1891 | .pointer = snd_mychip_pcm_pointer, | |
1892 | }; | |
1893 | ||
1894 | /* | |
1895 | * definitions of capture are omitted here... | |
1896 | */ | |
1897 | ||
1898 | /* create a pcm device */ | |
446ab5f5 | 1899 | static int __devinit snd_mychip_new_pcm(struct mychip *chip) |
1da177e4 | 1900 | { |
446ab5f5 | 1901 | struct snd_pcm *pcm; |
1da177e4 LT |
1902 | int err; |
1903 | ||
1904 | if ((err = snd_pcm_new(chip->card, "My Chip", 0, 1, 1, | |
1905 | &pcm)) < 0) | |
1906 | return err; | |
1907 | pcm->private_data = chip; | |
1908 | strcpy(pcm->name, "My Chip"); | |
1909 | chip->pcm = pcm; | |
1910 | /* set operators */ | |
1911 | snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_PLAYBACK, | |
1912 | &snd_mychip_playback_ops); | |
1913 | snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_CAPTURE, | |
1914 | &snd_mychip_capture_ops); | |
1915 | /* pre-allocation of buffers */ | |
1916 | /* NOTE: this may fail */ | |
1917 | snd_pcm_lib_preallocate_pages_for_all(pcm, SNDRV_DMA_TYPE_DEV, | |
1918 | snd_dma_pci_data(chip->pci), | |
1919 | 64*1024, 64*1024); | |
1920 | return 0; | |
1921 | } | |
1922 | ]]> | |
1923 | </programlisting> | |
1924 | </example> | |
1925 | </para> | |
1926 | </section> | |
1927 | ||
1928 | <section id="pcm-interface-constructor"> | |
1929 | <title>Constructor</title> | |
1930 | <para> | |
1931 | A pcm instance is allocated by <function>snd_pcm_new()</function> | |
1932 | function. It would be better to create a constructor for pcm, | |
1933 | namely, | |
1934 | ||
1935 | <informalexample> | |
1936 | <programlisting> | |
1937 | <![CDATA[ | |
446ab5f5 | 1938 | static int __devinit snd_mychip_new_pcm(struct mychip *chip) |
1da177e4 | 1939 | { |
446ab5f5 | 1940 | struct snd_pcm *pcm; |
1da177e4 LT |
1941 | int err; |
1942 | ||
1943 | if ((err = snd_pcm_new(chip->card, "My Chip", 0, 1, 1, | |
1944 | &pcm)) < 0) | |
1945 | return err; | |
1946 | pcm->private_data = chip; | |
1947 | strcpy(pcm->name, "My Chip"); | |
1948 | chip->pcm = pcm; | |
1949 | .... | |
1950 | return 0; | |
1951 | } | |
1952 | ]]> | |
1953 | </programlisting> | |
1954 | </informalexample> | |
1955 | </para> | |
1956 | ||
1957 | <para> | |
1958 | The <function>snd_pcm_new()</function> function takes the four | |
1959 | arguments. The first argument is the card pointer to which this | |
1960 | pcm is assigned, and the second is the ID string. | |
1961 | </para> | |
1962 | ||
1963 | <para> | |
1964 | The third argument (<parameter>index</parameter>, 0 in the | |
1965 | above) is the index of this new pcm. It begins from zero. When | |
1966 | you will create more than one pcm instances, specify the | |
1967 | different numbers in this argument. For example, | |
1968 | <parameter>index</parameter> = 1 for the second PCM device. | |
1969 | </para> | |
1970 | ||
1971 | <para> | |
1972 | The fourth and fifth arguments are the number of substreams | |
1973 | for playback and capture, respectively. Here both 1 are given in | |
1974 | the above example. When no playback or no capture is available, | |
1975 | pass 0 to the corresponding argument. | |
1976 | </para> | |
1977 | ||
1978 | <para> | |
1979 | If a chip supports multiple playbacks or captures, you can | |
1980 | specify more numbers, but they must be handled properly in | |
1981 | open/close, etc. callbacks. When you need to know which | |
1982 | substream you are referring to, then it can be obtained from | |
446ab5f5 | 1983 | struct <structname>snd_pcm_substream</structname> data passed to each callback |
1da177e4 LT |
1984 | as follows: |
1985 | ||
1986 | <informalexample> | |
1987 | <programlisting> | |
1988 | <![CDATA[ | |
446ab5f5 | 1989 | struct snd_pcm_substream *substream; |
1da177e4 LT |
1990 | int index = substream->number; |
1991 | ]]> | |
1992 | </programlisting> | |
1993 | </informalexample> | |
1994 | </para> | |
1995 | ||
1996 | <para> | |
1997 | After the pcm is created, you need to set operators for each | |
1998 | pcm stream. | |
1999 | ||
2000 | <informalexample> | |
2001 | <programlisting> | |
2002 | <![CDATA[ | |
2003 | snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_PLAYBACK, | |
2004 | &snd_mychip_playback_ops); | |
2005 | snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_CAPTURE, | |
2006 | &snd_mychip_capture_ops); | |
2007 | ]]> | |
2008 | </programlisting> | |
2009 | </informalexample> | |
2010 | </para> | |
2011 | ||
2012 | <para> | |
2013 | The operators are defined typically like this: | |
2014 | ||
2015 | <informalexample> | |
2016 | <programlisting> | |
2017 | <![CDATA[ | |
446ab5f5 | 2018 | static struct snd_pcm_ops snd_mychip_playback_ops = { |
1da177e4 LT |
2019 | .open = snd_mychip_pcm_open, |
2020 | .close = snd_mychip_pcm_close, | |
2021 | .ioctl = snd_pcm_lib_ioctl, | |
2022 | .hw_params = snd_mychip_pcm_hw_params, | |
2023 | .hw_free = snd_mychip_pcm_hw_free, | |
2024 | .prepare = snd_mychip_pcm_prepare, | |
2025 | .trigger = snd_mychip_pcm_trigger, | |
2026 | .pointer = snd_mychip_pcm_pointer, | |
2027 | }; | |
2028 | ]]> | |
2029 | </programlisting> | |
2030 | </informalexample> | |
2031 | ||
2032 | Each of callbacks is explained in the subsection | |
2033 | <link linkend="pcm-interface-operators"><citetitle> | |
2034 | Operators</citetitle></link>. | |
2035 | </para> | |
2036 | ||
2037 | <para> | |
2038 | After setting the operators, most likely you'd like to | |
2039 | pre-allocate the buffer. For the pre-allocation, simply call | |
2040 | the following: | |
2041 | ||
2042 | <informalexample> | |
2043 | <programlisting> | |
2044 | <![CDATA[ | |
2045 | snd_pcm_lib_preallocate_pages_for_all(pcm, SNDRV_DMA_TYPE_DEV, | |
2046 | snd_dma_pci_data(chip->pci), | |
2047 | 64*1024, 64*1024); | |
2048 | ]]> | |
2049 | </programlisting> | |
2050 | </informalexample> | |
2051 | ||
2052 | It will allocate up to 64kB buffer as default. The details of | |
2053 | buffer management will be described in the later section <link | |
2054 | linkend="buffer-and-memory"><citetitle>Buffer and Memory | |
2055 | Management</citetitle></link>. | |
2056 | </para> | |
2057 | ||
2058 | <para> | |
2059 | Additionally, you can set some extra information for this pcm | |
2060 | in pcm->info_flags. | |
2061 | The available values are defined as | |
2062 | <constant>SNDRV_PCM_INFO_XXX</constant> in | |
2063 | <filename><sound/asound.h></filename>, which is used for | |
2064 | the hardware definition (described later). When your soundchip | |
2065 | supports only half-duplex, specify like this: | |
2066 | ||
2067 | <informalexample> | |
2068 | <programlisting> | |
2069 | <![CDATA[ | |
2070 | pcm->info_flags = SNDRV_PCM_INFO_HALF_DUPLEX; | |
2071 | ]]> | |
2072 | </programlisting> | |
2073 | </informalexample> | |
2074 | </para> | |
2075 | </section> | |
2076 | ||
2077 | <section id="pcm-interface-destructor"> | |
2078 | <title>... And the Destructor?</title> | |
2079 | <para> | |
2080 | The destructor for a pcm instance is not always | |
2081 | necessary. Since the pcm device will be released by the middle | |
2082 | layer code automatically, you don't have to call destructor | |
2083 | explicitly. | |
2084 | </para> | |
2085 | ||
2086 | <para> | |
2087 | The destructor would be necessary when you created some | |
2088 | special records internally and need to release them. In such a | |
2089 | case, set the destructor function to | |
2090 | pcm->private_free: | |
2091 | ||
2092 | <example> | |
2093 | <title>PCM Instance with a Destructor</title> | |
2094 | <programlisting> | |
2095 | <![CDATA[ | |
446ab5f5 | 2096 | static void mychip_pcm_free(struct snd_pcm *pcm) |
1da177e4 | 2097 | { |
446ab5f5 | 2098 | struct mychip *chip = snd_pcm_chip(pcm); |
1da177e4 LT |
2099 | /* free your own data */ |
2100 | kfree(chip->my_private_pcm_data); | |
2101 | // do what you like else | |
2102 | .... | |
2103 | } | |
2104 | ||
446ab5f5 | 2105 | static int __devinit snd_mychip_new_pcm(struct mychip *chip) |
1da177e4 | 2106 | { |
446ab5f5 | 2107 | struct snd_pcm *pcm; |
1da177e4 LT |
2108 | .... |
2109 | /* allocate your own data */ | |
2110 | chip->my_private_pcm_data = kmalloc(...); | |
2111 | /* set the destructor */ | |
2112 | pcm->private_data = chip; | |
2113 | pcm->private_free = mychip_pcm_free; | |
2114 | .... | |
2115 | } | |
2116 | ]]> | |
2117 | </programlisting> | |
2118 | </example> | |
2119 | </para> | |
2120 | </section> | |
2121 | ||
2122 | <section id="pcm-interface-runtime"> | |
2123 | <title>Runtime Pointer - The Chest of PCM Information</title> | |
2124 | <para> | |
2125 | When the PCM substream is opened, a PCM runtime instance is | |
2126 | allocated and assigned to the substream. This pointer is | |
2127 | accessible via <constant>substream->runtime</constant>. | |
2128 | This runtime pointer holds the various information; it holds | |
2129 | the copy of hw_params and sw_params configurations, the buffer | |
2130 | pointers, mmap records, spinlocks, etc. Almost everyhing you | |
2131 | need for controlling the PCM can be found there. | |
2132 | </para> | |
2133 | ||
2134 | <para> | |
2135 | The definition of runtime instance is found in | |
2136 | <filename><sound/pcm.h></filename>. Here is the | |
2137 | copy from the file. | |
2138 | <informalexample> | |
2139 | <programlisting> | |
2140 | <![CDATA[ | |
2141 | struct _snd_pcm_runtime { | |
2142 | /* -- Status -- */ | |
446ab5f5 | 2143 | struct snd_pcm_substream *trigger_master; |
1da177e4 LT |
2144 | snd_timestamp_t trigger_tstamp; /* trigger timestamp */ |
2145 | int overrange; | |
2146 | snd_pcm_uframes_t avail_max; | |
2147 | snd_pcm_uframes_t hw_ptr_base; /* Position at buffer restart */ | |
2148 | snd_pcm_uframes_t hw_ptr_interrupt; /* Position at interrupt time*/ | |
2149 | ||
2150 | /* -- HW params -- */ | |
2151 | snd_pcm_access_t access; /* access mode */ | |
2152 | snd_pcm_format_t format; /* SNDRV_PCM_FORMAT_* */ | |
2153 | snd_pcm_subformat_t subformat; /* subformat */ | |
2154 | unsigned int rate; /* rate in Hz */ | |
2155 | unsigned int channels; /* channels */ | |
2156 | snd_pcm_uframes_t period_size; /* period size */ | |
2157 | unsigned int periods; /* periods */ | |
2158 | snd_pcm_uframes_t buffer_size; /* buffer size */ | |
2159 | unsigned int tick_time; /* tick time */ | |
2160 | snd_pcm_uframes_t min_align; /* Min alignment for the format */ | |
2161 | size_t byte_align; | |
2162 | unsigned int frame_bits; | |
2163 | unsigned int sample_bits; | |
2164 | unsigned int info; | |
2165 | unsigned int rate_num; | |
2166 | unsigned int rate_den; | |
2167 | ||
2168 | /* -- SW params -- */ | |
07799e75 | 2169 | struct timespec tstamp_mode; /* mmap timestamp is updated */ |
1da177e4 LT |
2170 | unsigned int period_step; |
2171 | unsigned int sleep_min; /* min ticks to sleep */ | |
2172 | snd_pcm_uframes_t xfer_align; /* xfer size need to be a multiple */ | |
2173 | snd_pcm_uframes_t start_threshold; | |
2174 | snd_pcm_uframes_t stop_threshold; | |
2175 | snd_pcm_uframes_t silence_threshold; /* Silence filling happens when | |
2176 | noise is nearest than this */ | |
2177 | snd_pcm_uframes_t silence_size; /* Silence filling size */ | |
2178 | snd_pcm_uframes_t boundary; /* pointers wrap point */ | |
2179 | ||
2180 | snd_pcm_uframes_t silenced_start; | |
2181 | snd_pcm_uframes_t silenced_size; | |
2182 | ||
2183 | snd_pcm_sync_id_t sync; /* hardware synchronization ID */ | |
2184 | ||
2185 | /* -- mmap -- */ | |
446ab5f5 TI |
2186 | volatile struct snd_pcm_mmap_status *status; |
2187 | volatile struct snd_pcm_mmap_control *control; | |
1da177e4 LT |
2188 | atomic_t mmap_count; |
2189 | ||
2190 | /* -- locking / scheduling -- */ | |
2191 | spinlock_t lock; | |
2192 | wait_queue_head_t sleep; | |
2193 | struct timer_list tick_timer; | |
2194 | struct fasync_struct *fasync; | |
2195 | ||
2196 | /* -- private section -- */ | |
2197 | void *private_data; | |
446ab5f5 | 2198 | void (*private_free)(struct snd_pcm_runtime *runtime); |
1da177e4 LT |
2199 | |
2200 | /* -- hardware description -- */ | |
446ab5f5 TI |
2201 | struct snd_pcm_hardware hw; |
2202 | struct snd_pcm_hw_constraints hw_constraints; | |
1da177e4 LT |
2203 | |
2204 | /* -- interrupt callbacks -- */ | |
446ab5f5 TI |
2205 | void (*transfer_ack_begin)(struct snd_pcm_substream *substream); |
2206 | void (*transfer_ack_end)(struct snd_pcm_substream *substream); | |
1da177e4 LT |
2207 | |
2208 | /* -- timer -- */ | |
2209 | unsigned int timer_resolution; /* timer resolution */ | |
2210 | ||
2211 | /* -- DMA -- */ | |
2212 | unsigned char *dma_area; /* DMA area */ | |
2213 | dma_addr_t dma_addr; /* physical bus address (not accessible from main CPU) */ | |
2214 | size_t dma_bytes; /* size of DMA area */ | |
2215 | ||
2216 | struct snd_dma_buffer *dma_buffer_p; /* allocated buffer */ | |
2217 | ||
2218 | #if defined(CONFIG_SND_PCM_OSS) || defined(CONFIG_SND_PCM_OSS_MODULE) | |
2219 | /* -- OSS things -- */ | |
446ab5f5 | 2220 | struct snd_pcm_oss_runtime oss; |
1da177e4 LT |
2221 | #endif |
2222 | }; | |
2223 | ]]> | |
2224 | </programlisting> | |
2225 | </informalexample> | |
2226 | </para> | |
2227 | ||
2228 | <para> | |
2229 | For the operators (callbacks) of each sound driver, most of | |
2230 | these records are supposed to be read-only. Only the PCM | |
2231 | middle-layer changes / updates these info. The exceptions are | |
2232 | the hardware description (hw), interrupt callbacks | |
2233 | (transfer_ack_xxx), DMA buffer information, and the private | |
2234 | data. Besides, if you use the standard buffer allocation | |
2235 | method via <function>snd_pcm_lib_malloc_pages()</function>, | |
2236 | you don't need to set the DMA buffer information by yourself. | |
2237 | </para> | |
2238 | ||
2239 | <para> | |
2240 | In the sections below, important records are explained. | |
2241 | </para> | |
2242 | ||
2243 | <section id="pcm-interface-runtime-hw"> | |
2244 | <title>Hardware Description</title> | |
2245 | <para> | |
446ab5f5 | 2246 | The hardware descriptor (struct <structname>snd_pcm_hardware</structname>) |
1da177e4 LT |
2247 | contains the definitions of the fundamental hardware |
2248 | configuration. Above all, you'll need to define this in | |
2249 | <link linkend="pcm-interface-operators-open-callback"><citetitle> | |
2250 | the open callback</citetitle></link>. | |
2251 | Note that the runtime instance holds the copy of the | |
2252 | descriptor, not the pointer to the existing descriptor. That | |
2253 | is, in the open callback, you can modify the copied descriptor | |
2254 | (<constant>runtime->hw</constant>) as you need. For example, if the maximum | |
2255 | number of channels is 1 only on some chip models, you can | |
2256 | still use the same hardware descriptor and change the | |
2257 | channels_max later: | |
2258 | <informalexample> | |
2259 | <programlisting> | |
2260 | <![CDATA[ | |
446ab5f5 | 2261 | struct snd_pcm_runtime *runtime = substream->runtime; |
1da177e4 LT |
2262 | ... |
2263 | runtime->hw = snd_mychip_playback_hw; /* common definition */ | |
2264 | if (chip->model == VERY_OLD_ONE) | |
2265 | runtime->hw.channels_max = 1; | |
2266 | ]]> | |
2267 | </programlisting> | |
2268 | </informalexample> | |
2269 | </para> | |
2270 | ||
2271 | <para> | |
2272 | Typically, you'll have a hardware descriptor like below: | |
2273 | <informalexample> | |
2274 | <programlisting> | |
2275 | <![CDATA[ | |
446ab5f5 | 2276 | static struct snd_pcm_hardware snd_mychip_playback_hw = { |
1da177e4 LT |
2277 | .info = (SNDRV_PCM_INFO_MMAP | |
2278 | SNDRV_PCM_INFO_INTERLEAVED | | |
2279 | SNDRV_PCM_INFO_BLOCK_TRANSFER | | |
2280 | SNDRV_PCM_INFO_MMAP_VALID), | |
2281 | .formats = SNDRV_PCM_FMTBIT_S16_LE, | |
2282 | .rates = SNDRV_PCM_RATE_8000_48000, | |
2283 | .rate_min = 8000, | |
2284 | .rate_max = 48000, | |
2285 | .channels_min = 2, | |
2286 | .channels_max = 2, | |
2287 | .buffer_bytes_max = 32768, | |
2288 | .period_bytes_min = 4096, | |
2289 | .period_bytes_max = 32768, | |
2290 | .periods_min = 1, | |
2291 | .periods_max = 1024, | |
2292 | }; | |
2293 | ]]> | |
2294 | </programlisting> | |
2295 | </informalexample> | |
2296 | </para> | |
2297 | ||
2298 | <para> | |
2299 | <itemizedlist> | |
2300 | <listitem><para> | |
2301 | The <structfield>info</structfield> field contains the type and | |
2302 | capabilities of this pcm. The bit flags are defined in | |
2303 | <filename><sound/asound.h></filename> as | |
2304 | <constant>SNDRV_PCM_INFO_XXX</constant>. Here, at least, you | |
2305 | have to specify whether the mmap is supported and which | |
2306 | interleaved format is supported. | |
2307 | When the mmap is supported, add | |
2308 | <constant>SNDRV_PCM_INFO_MMAP</constant> flag here. When the | |
2309 | hardware supports the interleaved or the non-interleaved | |
2310 | format, <constant>SNDRV_PCM_INFO_INTERLEAVED</constant> or | |
2311 | <constant>SNDRV_PCM_INFO_NONINTERLEAVED</constant> flag must | |
2312 | be set, respectively. If both are supported, you can set both, | |
2313 | too. | |
2314 | </para> | |
2315 | ||
2316 | <para> | |
2317 | In the above example, <constant>MMAP_VALID</constant> and | |
2318 | <constant>BLOCK_TRANSFER</constant> are specified for OSS mmap | |
2319 | mode. Usually both are set. Of course, | |
2320 | <constant>MMAP_VALID</constant> is set only if the mmap is | |
2321 | really supported. | |
2322 | </para> | |
2323 | ||
2324 | <para> | |
2325 | The other possible flags are | |
2326 | <constant>SNDRV_PCM_INFO_PAUSE</constant> and | |
2327 | <constant>SNDRV_PCM_INFO_RESUME</constant>. The | |
2328 | <constant>PAUSE</constant> bit means that the pcm supports the | |
2329 | <quote>pause</quote> operation, while the | |
2330 | <constant>RESUME</constant> bit means that the pcm supports | |
5fe76e4d TI |
2331 | the full <quote>suspend/resume</quote> operation. |
2332 | If <constant>PAUSE</constant> flag is set, | |
2333 | the <structfield>trigger</structfield> callback below | |
2334 | must handle the corresponding (pause push/release) commands. | |
2335 | The suspend/resume trigger commands can be defined even without | |
2336 | <constant>RESUME</constant> flag. See <link | |
2337 | linkend="power-management"><citetitle> | |
2338 | Power Management</citetitle></link> section for details. | |
1da177e4 LT |
2339 | </para> |
2340 | ||
2341 | <para> | |
2342 | When the PCM substreams can be synchronized (typically, | |
2343 | synchorinized start/stop of a playback and a capture streams), | |
2344 | you can give <constant>SNDRV_PCM_INFO_SYNC_START</constant>, | |
2345 | too. In this case, you'll need to check the linked-list of | |
2346 | PCM substreams in the trigger callback. This will be | |
2347 | described in the later section. | |
2348 | </para> | |
2349 | </listitem> | |
2350 | ||
2351 | <listitem> | |
2352 | <para> | |
2353 | <structfield>formats</structfield> field contains the bit-flags | |
2354 | of supported formats (<constant>SNDRV_PCM_FMTBIT_XXX</constant>). | |
2355 | If the hardware supports more than one format, give all or'ed | |
2356 | bits. In the example above, the signed 16bit little-endian | |
2357 | format is specified. | |
2358 | </para> | |
2359 | </listitem> | |
2360 | ||
2361 | <listitem> | |
2362 | <para> | |
2363 | <structfield>rates</structfield> field contains the bit-flags of | |
2364 | supported rates (<constant>SNDRV_PCM_RATE_XXX</constant>). | |
2365 | When the chip supports continuous rates, pass | |
2366 | <constant>CONTINUOUS</constant> bit additionally. | |
2367 | The pre-defined rate bits are provided only for typical | |
2368 | rates. If your chip supports unconventional rates, you need to add | |
2369 | <constant>KNOT</constant> bit and set up the hardware | |
2370 | constraint manually (explained later). | |
2371 | </para> | |
2372 | </listitem> | |
2373 | ||
2374 | <listitem> | |
2375 | <para> | |
2376 | <structfield>rate_min</structfield> and | |
2377 | <structfield>rate_max</structfield> define the minimal and | |
2378 | maximal sample rate. This should correspond somehow to | |
2379 | <structfield>rates</structfield> bits. | |
2380 | </para> | |
2381 | </listitem> | |
2382 | ||
2383 | <listitem> | |
2384 | <para> | |
2385 | <structfield>channel_min</structfield> and | |
2386 | <structfield>channel_max</structfield> | |
2387 | define, as you might already expected, the minimal and maximal | |
2388 | number of channels. | |
2389 | </para> | |
2390 | </listitem> | |
2391 | ||
2392 | <listitem> | |
2393 | <para> | |
2394 | <structfield>buffer_bytes_max</structfield> defines the | |
2395 | maximal buffer size in bytes. There is no | |
2396 | <structfield>buffer_bytes_min</structfield> field, since | |
2397 | it can be calculated from the minimal period size and the | |
2398 | minimal number of periods. | |
2399 | Meanwhile, <structfield>period_bytes_min</structfield> and | |
2400 | define the minimal and maximal size of the period in bytes. | |
2401 | <structfield>periods_max</structfield> and | |
2402 | <structfield>periods_min</structfield> define the maximal and | |
2403 | minimal number of periods in the buffer. | |
2404 | </para> | |
2405 | ||
2406 | <para> | |
2407 | The <quote>period</quote> is a term, that corresponds to | |
2408 | fragment in the OSS world. The period defines the size at | |
2409 | which the PCM interrupt is generated. This size strongly | |
2410 | depends on the hardware. | |
2411 | Generally, the smaller period size will give you more | |
2412 | interrupts, that is, more controls. | |
2413 | In the case of capture, this size defines the input latency. | |
2414 | On the other hand, the whole buffer size defines the | |
2415 | output latency for the playback direction. | |
2416 | </para> | |
2417 | </listitem> | |
2418 | ||
2419 | <listitem> | |
2420 | <para> | |
2421 | There is also a field <structfield>fifo_size</structfield>. | |
2422 | This specifies the size of the hardware FIFO, but it's not | |
2423 | used currently in the driver nor in the alsa-lib. So, you | |
2424 | can ignore this field. | |
2425 | </para> | |
2426 | </listitem> | |
2427 | </itemizedlist> | |
2428 | </para> | |
2429 | </section> | |
2430 | ||
2431 | <section id="pcm-interface-runtime-config"> | |
2432 | <title>PCM Configurations</title> | |
2433 | <para> | |
2434 | Ok, let's go back again to the PCM runtime records. | |
2435 | The most frequently referred records in the runtime instance are | |
2436 | the PCM configurations. | |
2437 | The PCM configurations are stored on runtime instance | |
2438 | after the application sends <type>hw_params</type> data via | |
2439 | alsa-lib. There are many fields copied from hw_params and | |
2440 | sw_params structs. For example, | |
2441 | <structfield>format</structfield> holds the format type | |
2442 | chosen by the application. This field contains the enum value | |
2443 | <constant>SNDRV_PCM_FORMAT_XXX</constant>. | |
2444 | </para> | |
2445 | ||
2446 | <para> | |
2447 | One thing to be noted is that the configured buffer and period | |
2448 | sizes are stored in <quote>frames</quote> in the runtime | |
2449 | In the ALSA world, 1 frame = channels * samples-size. | |
2450 | For conversion between frames and bytes, you can use the | |
2451 | helper functions, <function>frames_to_bytes()</function> and | |
2452 | <function>bytes_to_frames()</function>. | |
2453 | <informalexample> | |
2454 | <programlisting> | |
2455 | <![CDATA[ | |
2456 | period_bytes = frames_to_bytes(runtime, runtime->period_size); | |
2457 | ]]> | |
2458 | </programlisting> | |
2459 | </informalexample> | |
2460 | </para> | |
2461 | ||
2462 | <para> | |
2463 | Also, many software parameters (sw_params) are | |
2464 | stored in frames, too. Please check the type of the field. | |
2465 | <type>snd_pcm_uframes_t</type> is for the frames as unsigned | |
2466 | integer while <type>snd_pcm_sframes_t</type> is for the frames | |
2467 | as signed integer. | |
2468 | </para> | |
2469 | </section> | |
2470 | ||
2471 | <section id="pcm-interface-runtime-dma"> | |
2472 | <title>DMA Buffer Information</title> | |
2473 | <para> | |
2474 | The DMA buffer is defined by the following four fields, | |
2475 | <structfield>dma_area</structfield>, | |
2476 | <structfield>dma_addr</structfield>, | |
2477 | <structfield>dma_bytes</structfield> and | |
2478 | <structfield>dma_private</structfield>. | |
2479 | The <structfield>dma_area</structfield> holds the buffer | |
2480 | pointer (the logical address). You can call | |
2481 | <function>memcpy</function> from/to | |
2482 | this pointer. Meanwhile, <structfield>dma_addr</structfield> | |
2483 | holds the physical address of the buffer. This field is | |
2484 | specified only when the buffer is a linear buffer. | |
2485 | <structfield>dma_bytes</structfield> holds the size of buffer | |
2486 | in bytes. <structfield>dma_private</structfield> is used for | |
2487 | the ALSA DMA allocator. | |
2488 | </para> | |
2489 | ||
2490 | <para> | |
2491 | If you use a standard ALSA function, | |
2492 | <function>snd_pcm_lib_malloc_pages()</function>, for | |
2493 | allocating the buffer, these fields are set by the ALSA middle | |
2494 | layer, and you should <emphasis>not</emphasis> change them by | |
2495 | yourself. You can read them but not write them. | |
2496 | On the other hand, if you want to allocate the buffer by | |
2497 | yourself, you'll need to manage it in hw_params callback. | |
2498 | At least, <structfield>dma_bytes</structfield> is mandatory. | |
2499 | <structfield>dma_area</structfield> is necessary when the | |
2500 | buffer is mmapped. If your driver doesn't support mmap, this | |
2501 | field is not necessary. <structfield>dma_addr</structfield> | |
2502 | is also not mandatory. You can use | |
2503 | <structfield>dma_private</structfield> as you like, too. | |
2504 | </para> | |
2505 | </section> | |
2506 | ||
2507 | <section id="pcm-interface-runtime-status"> | |
2508 | <title>Running Status</title> | |
2509 | <para> | |
2510 | The running status can be referred via <constant>runtime->status</constant>. | |
446ab5f5 | 2511 | This is the pointer to struct <structname>snd_pcm_mmap_status</structname> |
1da177e4 LT |
2512 | record. For example, you can get the current DMA hardware |
2513 | pointer via <constant>runtime->status->hw_ptr</constant>. | |
2514 | </para> | |
2515 | ||
2516 | <para> | |
2517 | The DMA application pointer can be referred via | |
2518 | <constant>runtime->control</constant>, which points | |
446ab5f5 | 2519 | struct <structname>snd_pcm_mmap_control</structname> record. |
1da177e4 LT |
2520 | However, accessing directly to this value is not recommended. |
2521 | </para> | |
2522 | </section> | |
2523 | ||
2524 | <section id="pcm-interface-runtime-private"> | |
2525 | <title>Private Data</title> | |
2526 | <para> | |
2527 | You can allocate a record for the substream and store it in | |
2528 | <constant>runtime->private_data</constant>. Usually, this | |
2529 | done in | |
2530 | <link linkend="pcm-interface-operators-open-callback"><citetitle> | |
2531 | the open callback</citetitle></link>. | |
2532 | Don't mix this with <constant>pcm->private_data</constant>. | |
2533 | The <constant>pcm->private_data</constant> usually points the | |
2534 | chip instance assigned statically at the creation of PCM, while the | |
2535 | <constant>runtime->private_data</constant> points a dynamic | |
2536 | data created at the PCM open callback. | |
2537 | ||
2538 | <informalexample> | |
2539 | <programlisting> | |
2540 | <![CDATA[ | |
446ab5f5 | 2541 | static int snd_xxx_open(struct snd_pcm_substream *substream) |
1da177e4 | 2542 | { |
446ab5f5 | 2543 | struct my_pcm_data *data; |
1da177e4 LT |
2544 | .... |
2545 | data = kmalloc(sizeof(*data), GFP_KERNEL); | |
2546 | substream->runtime->private_data = data; | |
2547 | .... | |
2548 | } | |
2549 | ]]> | |
2550 | </programlisting> | |
2551 | </informalexample> | |
2552 | </para> | |
2553 | ||
2554 | <para> | |
2555 | The allocated object must be released in | |
2556 | <link linkend="pcm-interface-operators-open-callback"><citetitle> | |
2557 | the close callback</citetitle></link>. | |
2558 | </para> | |
2559 | </section> | |
2560 | ||
2561 | <section id="pcm-interface-runtime-intr"> | |
2562 | <title>Interrupt Callbacks</title> | |
2563 | <para> | |
2564 | The field <structfield>transfer_ack_begin</structfield> and | |
2565 | <structfield>transfer_ack_end</structfield> are called at | |
2566 | the beginning and the end of | |
2567 | <function>snd_pcm_period_elapsed()</function>, respectively. | |
2568 | </para> | |
2569 | </section> | |
2570 | ||
2571 | </section> | |
2572 | ||
2573 | <section id="pcm-interface-operators"> | |
2574 | <title>Operators</title> | |
2575 | <para> | |
2576 | OK, now let me explain the detail of each pcm callback | |
2577 | (<parameter>ops</parameter>). In general, every callback must | |
2578 | return 0 if successful, or a negative number with the error | |
2579 | number such as <constant>-EINVAL</constant> at any | |
2580 | error. | |
2581 | </para> | |
2582 | ||
2583 | <para> | |
2584 | The callback function takes at least the argument with | |
446ab5f5 | 2585 | <structname>snd_pcm_substream</structname> pointer. For retrieving the |
1da177e4 LT |
2586 | chip record from the given substream instance, you can use the |
2587 | following macro. | |
2588 | ||
2589 | <informalexample> | |
2590 | <programlisting> | |
2591 | <![CDATA[ | |
2592 | int xxx() { | |
446ab5f5 | 2593 | struct mychip *chip = snd_pcm_substream_chip(substream); |
1da177e4 LT |
2594 | .... |
2595 | } | |
2596 | ]]> | |
2597 | </programlisting> | |
2598 | </informalexample> | |
2599 | ||
2600 | The macro reads <constant>substream->private_data</constant>, | |
2601 | which is a copy of <constant>pcm->private_data</constant>. | |
2602 | You can override the former if you need to assign different data | |
2603 | records per PCM substream. For example, cmi8330 driver assigns | |
2604 | different private_data for playback and capture directions, | |
2605 | because it uses two different codecs (SB- and AD-compatible) for | |
2606 | different directions. | |
2607 | </para> | |
2608 | ||
2609 | <section id="pcm-interface-operators-open-callback"> | |
2610 | <title>open callback</title> | |
2611 | <para> | |
2612 | <informalexample> | |
2613 | <programlisting> | |
2614 | <![CDATA[ | |
446ab5f5 | 2615 | static int snd_xxx_open(struct snd_pcm_substream *substream); |
1da177e4 LT |
2616 | ]]> |
2617 | </programlisting> | |
2618 | </informalexample> | |
2619 | ||
2620 | This is called when a pcm substream is opened. | |
2621 | </para> | |
2622 | ||
2623 | <para> | |
2624 | At least, here you have to initialize the runtime->hw | |
2625 | record. Typically, this is done by like this: | |
2626 | ||
2627 | <informalexample> | |
2628 | <programlisting> | |
2629 | <![CDATA[ | |
446ab5f5 | 2630 | static int snd_xxx_open(struct snd_pcm_substream *substream) |
1da177e4 | 2631 | { |
446ab5f5 TI |
2632 | struct mychip *chip = snd_pcm_substream_chip(substream); |
2633 | struct snd_pcm_runtime *runtime = substream->runtime; | |
1da177e4 LT |
2634 | |
2635 | runtime->hw = snd_mychip_playback_hw; | |
2636 | return 0; | |
2637 | } | |
2638 | ]]> | |
2639 | </programlisting> | |
2640 | </informalexample> | |
2641 | ||
2642 | where <parameter>snd_mychip_playback_hw</parameter> is the | |
2643 | pre-defined hardware description. | |
2644 | </para> | |
2645 | ||
2646 | <para> | |
2647 | You can allocate a private data in this callback, as described | |
2648 | in <link linkend="pcm-interface-runtime-private"><citetitle> | |
2649 | Private Data</citetitle></link> section. | |
2650 | </para> | |
2651 | ||
2652 | <para> | |
2653 | If the hardware configuration needs more constraints, set the | |
2654 | hardware constraints here, too. | |
2655 | See <link linkend="pcm-interface-constraints"><citetitle> | |
2656 | Constraints</citetitle></link> for more details. | |
2657 | </para> | |
2658 | </section> | |
2659 | ||
2660 | <section id="pcm-interface-operators-close-callback"> | |
2661 | <title>close callback</title> | |
2662 | <para> | |
2663 | <informalexample> | |
2664 | <programlisting> | |
2665 | <![CDATA[ | |
446ab5f5 | 2666 | static int snd_xxx_close(struct snd_pcm_substream *substream); |
1da177e4 LT |
2667 | ]]> |
2668 | </programlisting> | |
2669 | </informalexample> | |
2670 | ||
2671 | Obviously, this is called when a pcm substream is closed. | |
2672 | </para> | |
2673 | ||
2674 | <para> | |
2675 | Any private instance for a pcm substream allocated in the | |
2676 | open callback will be released here. | |
2677 | ||
2678 | <informalexample> | |
2679 | <programlisting> | |
2680 | <![CDATA[ | |
446ab5f5 | 2681 | static int snd_xxx_close(struct snd_pcm_substream *substream) |
1da177e4 LT |
2682 | { |
2683 | .... | |
2684 | kfree(substream->runtime->private_data); | |
2685 | .... | |
2686 | } | |
2687 | ]]> | |
2688 | </programlisting> | |
2689 | </informalexample> | |
2690 | </para> | |
2691 | </section> | |
2692 | ||
2693 | <section id="pcm-interface-operators-ioctl-callback"> | |
2694 | <title>ioctl callback</title> | |
2695 | <para> | |
2696 | This is used for any special action to pcm ioctls. But | |
2697 | usually you can pass a generic ioctl callback, | |
2698 | <function>snd_pcm_lib_ioctl</function>. | |
2699 | </para> | |
2700 | </section> | |
2701 | ||
2702 | <section id="pcm-interface-operators-hw-params-callback"> | |
2703 | <title>hw_params callback</title> | |
2704 | <para> | |
2705 | <informalexample> | |
2706 | <programlisting> | |
2707 | <![CDATA[ | |
446ab5f5 TI |
2708 | static int snd_xxx_hw_params(struct snd_pcm_substream *substream, |
2709 | struct snd_pcm_hw_params *hw_params); | |
1da177e4 LT |
2710 | ]]> |
2711 | </programlisting> | |
2712 | </informalexample> | |
2713 | ||
2714 | This and <structfield>hw_free</structfield> callbacks exist | |
2715 | only on ALSA 0.9.x. | |
2716 | </para> | |
2717 | ||
2718 | <para> | |
2719 | This is called when the hardware parameter | |
2720 | (<structfield>hw_params</structfield>) is set | |
2721 | up by the application, | |
2722 | that is, once when the buffer size, the period size, the | |
2723 | format, etc. are defined for the pcm substream. | |
2724 | </para> | |
2725 | ||
2726 | <para> | |
2727 | Many hardware set-up should be done in this callback, | |
2728 | including the allocation of buffers. | |
2729 | </para> | |
2730 | ||
2731 | <para> | |
2732 | Parameters to be initialized are retrieved by | |
2733 | <function>params_xxx()</function> macros. For allocating a | |
2734 | buffer, you can call a helper function, | |
2735 | ||
2736 | <informalexample> | |
2737 | <programlisting> | |
2738 | <![CDATA[ | |
2739 | snd_pcm_lib_malloc_pages(substream, params_buffer_bytes(hw_params)); | |
2740 | ]]> | |
2741 | </programlisting> | |
2742 | </informalexample> | |
2743 | ||
2744 | <function>snd_pcm_lib_malloc_pages()</function> is available | |
2745 | only when the DMA buffers have been pre-allocated. | |
2746 | See the section <link | |
2747 | linkend="buffer-and-memory-buffer-types"><citetitle> | |
2748 | Buffer Types</citetitle></link> for more details. | |
2749 | </para> | |
2750 | ||
2751 | <para> | |
2752 | Note that this and <structfield>prepare</structfield> callbacks | |
2753 | may be called multiple times per initialization. | |
2754 | For example, the OSS emulation may | |
2755 | call these callbacks at each change via its ioctl. | |
2756 | </para> | |
2757 | ||
2758 | <para> | |
2759 | Thus, you need to take care not to allocate the same buffers | |
2760 | many times, which will lead to memory leak! Calling the | |
2761 | helper function above many times is OK. It will release the | |
2762 | previous buffer automatically when it was already allocated. | |
2763 | </para> | |
2764 | ||
2765 | <para> | |
2766 | Another note is that this callback is non-atomic | |
2767 | (schedulable). This is important, because the | |
2768 | <structfield>trigger</structfield> callback | |
2769 | is atomic (non-schedulable). That is, mutex or any | |
2770 | schedule-related functions are not available in | |
2771 | <structfield>trigger</structfield> callback. | |
2772 | Please see the subsection | |
2773 | <link linkend="pcm-interface-atomicity"><citetitle> | |
2774 | Atomicity</citetitle></link> for details. | |
2775 | </para> | |
2776 | </section> | |
2777 | ||
2778 | <section id="pcm-interface-operators-hw-free-callback"> | |
2779 | <title>hw_free callback</title> | |
2780 | <para> | |
2781 | <informalexample> | |
2782 | <programlisting> | |
2783 | <![CDATA[ | |
446ab5f5 | 2784 | static int snd_xxx_hw_free(struct snd_pcm_substream *substream); |
1da177e4 LT |
2785 | ]]> |
2786 | </programlisting> | |
2787 | </informalexample> | |
2788 | </para> | |
2789 | ||
2790 | <para> | |
2791 | This is called to release the resources allocated via | |
2792 | <structfield>hw_params</structfield>. For example, releasing the | |
2793 | buffer via | |
2794 | <function>snd_pcm_lib_malloc_pages()</function> is done by | |
2795 | calling the following: | |
2796 | ||
2797 | <informalexample> | |
2798 | <programlisting> | |
2799 | <![CDATA[ | |
2800 | snd_pcm_lib_free_pages(substream); | |
2801 | ]]> | |
2802 | </programlisting> | |
2803 | </informalexample> | |
2804 | </para> | |
2805 | ||
2806 | <para> | |
2807 | This function is always called before the close callback is called. | |
2808 | Also, the callback may be called multiple times, too. | |
2809 | Keep track whether the resource was already released. | |
2810 | </para> | |
2811 | </section> | |
2812 | ||
2813 | <section id="pcm-interface-operators-prepare-callback"> | |
2814 | <title>prepare callback</title> | |
2815 | <para> | |
2816 | <informalexample> | |
2817 | <programlisting> | |
2818 | <![CDATA[ | |
446ab5f5 | 2819 | static int snd_xxx_prepare(struct snd_pcm_substream *substream); |
1da177e4 LT |
2820 | ]]> |
2821 | </programlisting> | |
2822 | </informalexample> | |
2823 | </para> | |
2824 | ||
2825 | <para> | |
2826 | This callback is called when the pcm is | |
2827 | <quote>prepared</quote>. You can set the format type, sample | |
2828 | rate, etc. here. The difference from | |
2829 | <structfield>hw_params</structfield> is that the | |
2830 | <structfield>prepare</structfield> callback will be called at each | |
2831 | time | |
2832 | <function>snd_pcm_prepare()</function> is called, i.e. when | |
2833 | recovered after underruns, etc. | |
2834 | </para> | |
2835 | ||
2836 | <para> | |
2837 | Note that this callback became non-atomic since the recent version. | |
0b28002f | 2838 | You can use schedule-related functions safely in this callback now. |
1da177e4 LT |
2839 | </para> |
2840 | ||
2841 | <para> | |
2842 | In this and the following callbacks, you can refer to the | |
2843 | values via the runtime record, | |
2844 | substream->runtime. | |
2845 | For example, to get the current | |
2846 | rate, format or channels, access to | |
2847 | runtime->rate, | |
2848 | runtime->format or | |
2849 | runtime->channels, respectively. | |
2850 | The physical address of the allocated buffer is set to | |
2851 | runtime->dma_area. The buffer and period sizes are | |
2852 | in runtime->buffer_size and runtime->period_size, | |
2853 | respectively. | |
2854 | </para> | |
2855 | ||
2856 | <para> | |
2857 | Be careful that this callback will be called many times at | |
2858 | each set up, too. | |
2859 | </para> | |
2860 | </section> | |
2861 | ||
2862 | <section id="pcm-interface-operators-trigger-callback"> | |
2863 | <title>trigger callback</title> | |
2864 | <para> | |
2865 | <informalexample> | |
2866 | <programlisting> | |
2867 | <![CDATA[ | |
446ab5f5 | 2868 | static int snd_xxx_trigger(struct snd_pcm_substream *substream, int cmd); |
1da177e4 LT |
2869 | ]]> |
2870 | </programlisting> | |
2871 | </informalexample> | |
2872 | ||
2873 | This is called when the pcm is started, stopped or paused. | |
2874 | </para> | |
2875 | ||
2876 | <para> | |
2877 | Which action is specified in the second argument, | |
2878 | <constant>SNDRV_PCM_TRIGGER_XXX</constant> in | |
2879 | <filename><sound/pcm.h></filename>. At least, | |
2880 | <constant>START</constant> and <constant>STOP</constant> | |
2881 | commands must be defined in this callback. | |
2882 | ||
2883 | <informalexample> | |
2884 | <programlisting> | |
2885 | <![CDATA[ | |
2886 | switch (cmd) { | |
2887 | case SNDRV_PCM_TRIGGER_START: | |
2888 | // do something to start the PCM engine | |
2889 | break; | |
2890 | case SNDRV_PCM_TRIGGER_STOP: | |
2891 | // do something to stop the PCM engine | |
2892 | break; | |
2893 | default: | |
2894 | return -EINVAL; | |
2895 | } | |
2896 | ]]> | |
2897 | </programlisting> | |
2898 | </informalexample> | |
2899 | </para> | |
2900 | ||
2901 | <para> | |
2902 | When the pcm supports the pause operation (given in info | |
2903 | field of the hardware table), <constant>PAUSE_PUSE</constant> | |
2904 | and <constant>PAUSE_RELEASE</constant> commands must be | |
2905 | handled here, too. The former is the command to pause the pcm, | |
2906 | and the latter to restart the pcm again. | |
2907 | </para> | |
2908 | ||
2909 | <para> | |
5fe76e4d TI |
2910 | When the pcm supports the suspend/resume operation, |
2911 | regardless of full or partial suspend/resume support, | |
1da177e4 LT |
2912 | <constant>SUSPEND</constant> and <constant>RESUME</constant> |
2913 | commands must be handled, too. | |
2914 | These commands are issued when the power-management status is | |
2915 | changed. Obviously, the <constant>SUSPEND</constant> and | |
2916 | <constant>RESUME</constant> | |
2917 | do suspend and resume of the pcm substream, and usually, they | |
2918 | are identical with <constant>STOP</constant> and | |
2919 | <constant>START</constant> commands, respectively. | |
5fe76e4d TI |
2920 | See <link linkend="power-management"><citetitle> |
2921 | Power Management</citetitle></link> section for details. | |
1da177e4 LT |
2922 | </para> |
2923 | ||
2924 | <para> | |
2925 | As mentioned, this callback is atomic. You cannot call | |
2926 | the function going to sleep. | |
2927 | The trigger callback should be as minimal as possible, | |
2928 | just really triggering the DMA. The other stuff should be | |
2929 | initialized hw_params and prepare callbacks properly | |
2930 | beforehand. | |
2931 | </para> | |
2932 | </section> | |
2933 | ||
2934 | <section id="pcm-interface-operators-pointer-callback"> | |
2935 | <title>pointer callback</title> | |
2936 | <para> | |
2937 | <informalexample> | |
2938 | <programlisting> | |
2939 | <![CDATA[ | |
446ab5f5 | 2940 | static snd_pcm_uframes_t snd_xxx_pointer(struct snd_pcm_substream *substream) |
1da177e4 LT |
2941 | ]]> |
2942 | </programlisting> | |
2943 | </informalexample> | |
2944 | ||
2945 | This callback is called when the PCM middle layer inquires | |
2946 | the current hardware position on the buffer. The position must | |
2947 | be returned in frames (which was in bytes on ALSA 0.5.x), | |
2948 | ranged from 0 to buffer_size - 1. | |
2949 | </para> | |
2950 | ||
2951 | <para> | |
2952 | This is called usually from the buffer-update routine in the | |
2953 | pcm middle layer, which is invoked when | |
2954 | <function>snd_pcm_period_elapsed()</function> is called in the | |
2955 | interrupt routine. Then the pcm middle layer updates the | |
2956 | position and calculates the available space, and wakes up the | |
2957 | sleeping poll threads, etc. | |
2958 | </para> | |
2959 | ||
2960 | <para> | |
2961 | This callback is also atomic. | |
2962 | </para> | |
2963 | </section> | |
2964 | ||
2965 | <section id="pcm-interface-operators-copy-silence"> | |
2966 | <title>copy and silence callbacks</title> | |
2967 | <para> | |
2968 | These callbacks are not mandatory, and can be omitted in | |
2969 | most cases. These callbacks are used when the hardware buffer | |
2970 | cannot be on the normal memory space. Some chips have their | |
2971 | own buffer on the hardware which is not mappable. In such a | |
2972 | case, you have to transfer the data manually from the memory | |
2973 | buffer to the hardware buffer. Or, if the buffer is | |
2974 | non-contiguous on both physical and virtual memory spaces, | |
2975 | these callbacks must be defined, too. | |
2976 | </para> | |
2977 | ||
2978 | <para> | |
2979 | If these two callbacks are defined, copy and set-silence | |
2980 | operations are done by them. The detailed will be described in | |
2981 | the later section <link | |
2982 | linkend="buffer-and-memory"><citetitle>Buffer and Memory | |
2983 | Management</citetitle></link>. | |
2984 | </para> | |
2985 | </section> | |
2986 | ||
2987 | <section id="pcm-interface-operators-ack"> | |
2988 | <title>ack callback</title> | |
2989 | <para> | |
2990 | This callback is also not mandatory. This callback is called | |
2991 | when the appl_ptr is updated in read or write operations. | |
2992 | Some drivers like emu10k1-fx and cs46xx need to track the | |
2993 | current appl_ptr for the internal buffer, and this callback | |
2994 | is useful only for such a purpose. | |
2995 | </para> | |
2996 | <para> | |
2997 | This callback is atomic. | |
2998 | </para> | |
2999 | </section> | |
3000 | ||
3001 | <section id="pcm-interface-operators-page-callback"> | |
3002 | <title>page callback</title> | |
3003 | ||
3004 | <para> | |
3005 | This callback is also not mandatory. This callback is used | |
3006 | mainly for the non-contiguous buffer. The mmap calls this | |
3007 | callback to get the page address. Some examples will be | |
3008 | explained in the later section <link | |
3009 | linkend="buffer-and-memory"><citetitle>Buffer and Memory | |
3010 | Management</citetitle></link>, too. | |
3011 | </para> | |
3012 | </section> | |
3013 | </section> | |
3014 | ||
3015 | <section id="pcm-interface-interrupt-handler"> | |
3016 | <title>Interrupt Handler</title> | |
3017 | <para> | |
3018 | The rest of pcm stuff is the PCM interrupt handler. The | |
3019 | role of PCM interrupt handler in the sound driver is to update | |
3020 | the buffer position and to tell the PCM middle layer when the | |
3021 | buffer position goes across the prescribed period size. To | |
3022 | inform this, call <function>snd_pcm_period_elapsed()</function> | |
3023 | function. | |
3024 | </para> | |
3025 | ||
3026 | <para> | |
3027 | There are several types of sound chips to generate the interrupts. | |
3028 | </para> | |
3029 | ||
3030 | <section id="pcm-interface-interrupt-handler-boundary"> | |
3031 | <title>Interrupts at the period (fragment) boundary</title> | |
3032 | <para> | |
3033 | This is the most frequently found type: the hardware | |
3034 | generates an interrupt at each period boundary. | |
3035 | In this case, you can call | |
3036 | <function>snd_pcm_period_elapsed()</function> at each | |
3037 | interrupt. | |
3038 | </para> | |
3039 | ||
3040 | <para> | |
3041 | <function>snd_pcm_period_elapsed()</function> takes the | |
3042 | substream pointer as its argument. Thus, you need to keep the | |
3043 | substream pointer accessible from the chip instance. For | |
3044 | example, define substream field in the chip record to hold the | |
3045 | current running substream pointer, and set the pointer value | |
3046 | at open callback (and reset at close callback). | |
3047 | </para> | |
3048 | ||
3049 | <para> | |
0418726b | 3050 | If you acquire a spinlock in the interrupt handler, and the |
1da177e4 LT |
3051 | lock is used in other pcm callbacks, too, then you have to |
3052 | release the lock before calling | |
3053 | <function>snd_pcm_period_elapsed()</function>, because | |
3054 | <function>snd_pcm_period_elapsed()</function> calls other pcm | |
3055 | callbacks inside. | |
3056 | </para> | |
3057 | ||
3058 | <para> | |
3059 | A typical coding would be like: | |
3060 | ||
3061 | <example> | |
3062 | <title>Interrupt Handler Case #1</title> | |
3063 | <programlisting> | |
3064 | <![CDATA[ | |
3065 | static irqreturn_t snd_mychip_interrupt(int irq, void *dev_id, | |
3066 | struct pt_regs *regs) | |
3067 | { | |
446ab5f5 | 3068 | struct mychip *chip = dev_id; |
1da177e4 LT |
3069 | spin_lock(&chip->lock); |
3070 | .... | |
3071 | if (pcm_irq_invoked(chip)) { | |
3072 | /* call updater, unlock before it */ | |
3073 | spin_unlock(&chip->lock); | |
3074 | snd_pcm_period_elapsed(chip->substream); | |
3075 | spin_lock(&chip->lock); | |
3076 | // acknowledge the interrupt if necessary | |
3077 | } | |
3078 | .... | |
3079 | spin_unlock(&chip->lock); | |
3080 | return IRQ_HANDLED; | |
3081 | } | |
3082 | ]]> | |
3083 | </programlisting> | |
3084 | </example> | |
3085 | </para> | |
3086 | </section> | |
3087 | ||
3088 | <section id="pcm-interface-interrupt-handler-timer"> | |
3089 | <title>High-frequent timer interrupts</title> | |
3090 | <para> | |
3091 | This is the case when the hardware doesn't generate interrupts | |
3092 | at the period boundary but do timer-interrupts at the fixed | |
3093 | timer rate (e.g. es1968 or ymfpci drivers). | |
3094 | In this case, you need to check the current hardware | |
3095 | position and accumulates the processed sample length at each | |
3096 | interrupt. When the accumulated size overcomes the period | |
3097 | size, call | |
3098 | <function>snd_pcm_period_elapsed()</function> and reset the | |
3099 | accumulator. | |
3100 | </para> | |
3101 | ||
3102 | <para> | |
3103 | A typical coding would be like the following. | |
3104 | ||
3105 | <example> | |
3106 | <title>Interrupt Handler Case #2</title> | |
3107 | <programlisting> | |
3108 | <![CDATA[ | |
3109 | static irqreturn_t snd_mychip_interrupt(int irq, void *dev_id, | |
3110 | struct pt_regs *regs) | |
3111 | { | |
446ab5f5 | 3112 | struct mychip *chip = dev_id; |
1da177e4 LT |
3113 | spin_lock(&chip->lock); |
3114 | .... | |
3115 | if (pcm_irq_invoked(chip)) { | |
3116 | unsigned int last_ptr, size; | |
3117 | /* get the current hardware pointer (in frames) */ | |
3118 | last_ptr = get_hw_ptr(chip); | |
3119 | /* calculate the processed frames since the | |
3120 | * last update | |
3121 | */ | |
3122 | if (last_ptr < chip->last_ptr) | |
3123 | size = runtime->buffer_size + last_ptr | |
3124 | - chip->last_ptr; | |
3125 | else | |
3126 | size = last_ptr - chip->last_ptr; | |
3127 | /* remember the last updated point */ | |
3128 | chip->last_ptr = last_ptr; | |
3129 | /* accumulate the size */ | |
3130 | chip->size += size; | |
3131 | /* over the period boundary? */ | |
3132 | if (chip->size >= runtime->period_size) { | |
3133 | /* reset the accumulator */ | |
3134 | chip->size %= runtime->period_size; | |
3135 | /* call updater */ | |
3136 | spin_unlock(&chip->lock); | |
3137 | snd_pcm_period_elapsed(substream); | |
3138 | spin_lock(&chip->lock); | |
3139 | } | |
3140 | // acknowledge the interrupt if necessary | |
3141 | } | |
3142 | .... | |
3143 | spin_unlock(&chip->lock); | |
3144 | return IRQ_HANDLED; | |
3145 | } | |
3146 | ]]> | |
3147 | </programlisting> | |
3148 | </example> | |
3149 | </para> | |
3150 | </section> | |
3151 | ||
3152 | <section id="pcm-interface-interrupt-handler-both"> | |
3153 | <title>On calling <function>snd_pcm_period_elapsed()</function></title> | |
3154 | <para> | |
3155 | In both cases, even if more than one period are elapsed, you | |
3156 | don't have to call | |
3157 | <function>snd_pcm_period_elapsed()</function> many times. Call | |
3158 | only once. And the pcm layer will check the current hardware | |
3159 | pointer and update to the latest status. | |
3160 | </para> | |
3161 | </section> | |
3162 | </section> | |
3163 | ||
3164 | <section id="pcm-interface-atomicity"> | |
3165 | <title>Atomicity</title> | |
3166 | <para> | |
3167 | One of the most important (and thus difficult to debug) problem | |
3168 | on the kernel programming is the race condition. | |
3169 | On linux kernel, usually it's solved via spin-locks or | |
3170 | semaphores. In general, if the race condition may | |
3171 | happen in the interrupt handler, it's handled as atomic, and you | |
3172 | have to use spinlock for protecting the critical session. If it | |
3173 | never happens in the interrupt and it may take relatively long | |
3174 | time, you should use semaphore. | |
3175 | </para> | |
3176 | ||
3177 | <para> | |
3178 | As already seen, some pcm callbacks are atomic and some are | |
3179 | not. For example, <parameter>hw_params</parameter> callback is | |
3180 | non-atomic, while <parameter>trigger</parameter> callback is | |
3181 | atomic. This means, the latter is called already in a spinlock | |
3182 | held by the PCM middle layer. Please take this atomicity into | |
3183 | account when you use a spinlock or a semaphore in the callbacks. | |
3184 | </para> | |
3185 | ||
3186 | <para> | |
3187 | In the atomic callbacks, you cannot use functions which may call | |
3188 | <function>schedule</function> or go to | |
3189 | <function>sleep</function>. The semaphore and mutex do sleep, | |
3190 | and hence they cannot be used inside the atomic callbacks | |
3191 | (e.g. <parameter>trigger</parameter> callback). | |
3192 | For taking a certain delay in such a callback, please use | |
3193 | <function>udelay()</function> or <function>mdelay()</function>. | |
3194 | </para> | |
3195 | ||
3196 | <para> | |
3197 | All three atomic callbacks (trigger, pointer, and ack) are | |
3198 | called with local interrupts disabled. | |
3199 | </para> | |
3200 | ||
3201 | </section> | |
3202 | <section id="pcm-interface-constraints"> | |
3203 | <title>Constraints</title> | |
3204 | <para> | |
3205 | If your chip supports unconventional sample rates, or only the | |
3206 | limited samples, you need to set a constraint for the | |
3207 | condition. | |
3208 | </para> | |
3209 | ||
3210 | <para> | |
3211 | For example, in order to restrict the sample rates in the some | |
3212 | supported values, use | |
3213 | <function>snd_pcm_hw_constraint_list()</function>. | |
3214 | You need to call this function in the open callback. | |
3215 | ||
3216 | <example> | |
3217 | <title>Example of Hardware Constraints</title> | |
3218 | <programlisting> | |
3219 | <![CDATA[ | |
3220 | static unsigned int rates[] = | |
3221 | {4000, 10000, 22050, 44100}; | |
446ab5f5 | 3222 | static struct snd_pcm_hw_constraint_list constraints_rates = { |
1da177e4 LT |
3223 | .count = ARRAY_SIZE(rates), |
3224 | .list = rates, | |
3225 | .mask = 0, | |
3226 | }; | |
3227 | ||
446ab5f5 | 3228 | static int snd_mychip_pcm_open(struct snd_pcm_substream *substream) |
1da177e4 LT |
3229 | { |
3230 | int err; | |
3231 | .... | |
3232 | err = snd_pcm_hw_constraint_list(substream->runtime, 0, | |
3233 | SNDRV_PCM_HW_PARAM_RATE, | |
3234 | &constraints_rates); | |
3235 | if (err < 0) | |
3236 | return err; | |
3237 | .... | |
3238 | } | |
3239 | ]]> | |
3240 | </programlisting> | |
3241 | </example> | |
3242 | </para> | |
3243 | ||
3244 | <para> | |
3245 | There are many different constraints. | |
3246 | Look in <filename>sound/pcm.h</filename> for a complete list. | |
3247 | You can even define your own constraint rules. | |
3248 | For example, let's suppose my_chip can manage a substream of 1 channel | |
3249 | if and only if the format is S16_LE, otherwise it supports any format | |
446ab5f5 | 3250 | specified in the <structname>snd_pcm_hardware</structname> stucture (or in any |
1da177e4 LT |
3251 | other constraint_list). You can build a rule like this: |
3252 | ||
3253 | <example> | |
3254 | <title>Example of Hardware Constraints for Channels</title> | |
3255 | <programlisting> | |
3256 | <![CDATA[ | |
446ab5f5 TI |
3257 | static int hw_rule_format_by_channels(struct snd_pcm_hw_params *params, |
3258 | struct snd_pcm_hw_rule *rule) | |
1da177e4 | 3259 | { |
446ab5f5 TI |
3260 | struct snd_interval *c = hw_param_interval(params, |
3261 | SNDRV_PCM_HW_PARAM_CHANNELS); | |
3262 | struct snd_mask *f = hw_param_mask(params, SNDRV_PCM_HW_PARAM_FORMAT); | |
3263 | struct snd_mask fmt; | |
1da177e4 LT |
3264 | |
3265 | snd_mask_any(&fmt); /* Init the struct */ | |
3266 | if (c->min < 2) { | |
3267 | fmt.bits[0] &= SNDRV_PCM_FMTBIT_S16_LE; | |
3268 | return snd_mask_refine(f, &fmt); | |
3269 | } | |
3270 | return 0; | |
3271 | } | |
3272 | ]]> | |
3273 | </programlisting> | |
3274 | </example> | |
3275 | </para> | |
3276 | ||
3277 | <para> | |
3278 | Then you need to call this function to add your rule: | |
3279 | ||
3280 | <informalexample> | |
3281 | <programlisting> | |
3282 | <![CDATA[ | |
3283 | snd_pcm_hw_rule_add(substream->runtime, 0, SNDRV_PCM_HW_PARAM_CHANNELS, | |
3284 | hw_rule_channels_by_format, 0, SNDRV_PCM_HW_PARAM_FORMAT, | |
3285 | -1); | |
3286 | ]]> | |
3287 | </programlisting> | |
3288 | </informalexample> | |
3289 | </para> | |
3290 | ||
3291 | <para> | |
3292 | The rule function is called when an application sets the number of | |
3293 | channels. But an application can set the format before the number of | |
3294 | channels. Thus you also need to define the inverse rule: | |
3295 | ||
3296 | <example> | |
3297 | <title>Example of Hardware Constraints for Channels</title> | |
3298 | <programlisting> | |
3299 | <![CDATA[ | |
446ab5f5 TI |
3300 | static int hw_rule_channels_by_format(struct snd_pcm_hw_params *params, |
3301 | struct snd_pcm_hw_rule *rule) | |
1da177e4 | 3302 | { |
446ab5f5 TI |
3303 | struct snd_interval *c = hw_param_interval(params, |
3304 | SNDRV_PCM_HW_PARAM_CHANNELS); | |
3305 | struct snd_mask *f = hw_param_mask(params, SNDRV_PCM_HW_PARAM_FORMAT); | |
3306 | struct snd_interval ch; | |
1da177e4 LT |
3307 | |
3308 | snd_interval_any(&ch); | |
3309 | if (f->bits[0] == SNDRV_PCM_FMTBIT_S16_LE) { | |
3310 | ch.min = ch.max = 1; | |
3311 | ch.integer = 1; | |
3312 | return snd_interval_refine(c, &ch); | |
3313 | } | |
3314 | return 0; | |
3315 | } | |
3316 | ]]> | |
3317 | </programlisting> | |
3318 | </example> | |
3319 | </para> | |
3320 | ||
3321 | <para> | |
3322 | ...and in the open callback: | |
3323 | <informalexample> | |
3324 | <programlisting> | |
3325 | <![CDATA[ | |
3326 | snd_pcm_hw_rule_add(substream->runtime, 0, SNDRV_PCM_HW_PARAM_FORMAT, | |
3327 | hw_rule_format_by_channels, 0, SNDRV_PCM_HW_PARAM_CHANNELS, | |
3328 | -1); | |
3329 | ]]> | |
3330 | </programlisting> | |
3331 | </informalexample> | |
3332 | </para> | |
3333 | ||
3334 | <para> | |
3335 | I won't explain more details here, rather I | |
3336 | would like to say, <quote>Luke, use the source.</quote> | |
3337 | </para> | |
3338 | </section> | |
3339 | ||
3340 | </chapter> | |
3341 | ||
3342 | ||
3343 | <!-- ****************************************************** --> | |
3344 | <!-- Control Interface --> | |
3345 | <!-- ****************************************************** --> | |
3346 | <chapter id="control-interface"> | |
3347 | <title>Control Interface</title> | |
3348 | ||
3349 | <section id="control-interface-general"> | |
3350 | <title>General</title> | |
3351 | <para> | |
3352 | The control interface is used widely for many switches, | |
3353 | sliders, etc. which are accessed from the user-space. Its most | |
3354 | important use is the mixer interface. In other words, on ALSA | |
3355 | 0.9.x, all the mixer stuff is implemented on the control kernel | |
3356 | API (while there was an independent mixer kernel API on 0.5.x). | |
3357 | </para> | |
3358 | ||
3359 | <para> | |
3360 | ALSA has a well-defined AC97 control module. If your chip | |
3361 | supports only the AC97 and nothing else, you can skip this | |
3362 | section. | |
3363 | </para> | |
3364 | ||
3365 | <para> | |
3366 | The control API is defined in | |
3367 | <filename><sound/control.h></filename>. | |
3368 | Include this file if you add your own controls. | |
3369 | </para> | |
3370 | </section> | |
3371 | ||
3372 | <section id="control-interface-definition"> | |
3373 | <title>Definition of Controls</title> | |
3374 | <para> | |
3375 | For creating a new control, you need to define the three | |
3376 | callbacks: <structfield>info</structfield>, | |
3377 | <structfield>get</structfield> and | |
3378 | <structfield>put</structfield>. Then, define a | |
446ab5f5 | 3379 | struct <structname>snd_kcontrol_new</structname> record, such as: |
1da177e4 LT |
3380 | |
3381 | <example> | |
3382 | <title>Definition of a Control</title> | |
3383 | <programlisting> | |
3384 | <![CDATA[ | |
446ab5f5 | 3385 | static struct snd_kcontrol_new my_control __devinitdata = { |
1da177e4 LT |
3386 | .iface = SNDRV_CTL_ELEM_IFACE_MIXER, |
3387 | .name = "PCM Playback Switch", | |
3388 | .index = 0, | |
3389 | .access = SNDRV_CTL_ELEM_ACCESS_READWRITE, | |
0b7bed4e | 3390 | .private_value = 0xffff, |
1da177e4 LT |
3391 | .info = my_control_info, |
3392 | .get = my_control_get, | |
3393 | .put = my_control_put | |
3394 | }; | |
3395 | ]]> | |
3396 | </programlisting> | |
3397 | </example> | |
3398 | </para> | |
3399 | ||
3400 | <para> | |
3401 | Most likely the control is created via | |
3402 | <function>snd_ctl_new1()</function>, and in such a case, you can | |
3403 | add <parameter>__devinitdata</parameter> prefix to the | |
3404 | definition like above. | |
3405 | </para> | |
3406 | ||
3407 | <para> | |
3408 | The <structfield>iface</structfield> field specifies the type of | |
67ed4161 CL |
3409 | the control, <constant>SNDRV_CTL_ELEM_IFACE_XXX</constant>, which |
3410 | is usually <constant>MIXER</constant>. | |
3411 | Use <constant>CARD</constant> for global controls that are not | |
3412 | logically part of the mixer. | |
3413 | If the control is closely associated with some specific device on | |
3414 | the sound card, use <constant>HWDEP</constant>, | |
3415 | <constant>PCM</constant>, <constant>RAWMIDI</constant>, | |
3416 | <constant>TIMER</constant>, or <constant>SEQUENCER</constant>, and | |
3417 | specify the device number with the | |
3418 | <structfield>device</structfield> and | |
3419 | <structfield>subdevice</structfield> fields. | |
1da177e4 LT |
3420 | </para> |
3421 | ||
3422 | <para> | |
3423 | The <structfield>name</structfield> is the name identifier | |
3424 | string. On ALSA 0.9.x, the control name is very important, | |
3425 | because its role is classified from its name. There are | |
3426 | pre-defined standard control names. The details are described in | |
3427 | the subsection | |
3428 | <link linkend="control-interface-control-names"><citetitle> | |
3429 | Control Names</citetitle></link>. | |
3430 | </para> | |
3431 | ||
3432 | <para> | |
3433 | The <structfield>index</structfield> field holds the index number | |
3434 | of this control. If there are several different controls with | |
3435 | the same name, they can be distinguished by the index | |
3436 | number. This is the case when | |
3437 | several codecs exist on the card. If the index is zero, you can | |
3438 | omit the definition above. | |
3439 | </para> | |
3440 | ||
3441 | <para> | |
3442 | The <structfield>access</structfield> field contains the access | |
3443 | type of this control. Give the combination of bit masks, | |
3444 | <constant>SNDRV_CTL_ELEM_ACCESS_XXX</constant>, there. | |
3445 | The detailed will be explained in the subsection | |
3446 | <link linkend="control-interface-access-flags"><citetitle> | |
3447 | Access Flags</citetitle></link>. | |
3448 | </para> | |
3449 | ||
3450 | <para> | |
0b7bed4e | 3451 | The <structfield>private_value</structfield> field contains |
1da177e4 LT |
3452 | an arbitrary long integer value for this record. When using |
3453 | generic <structfield>info</structfield>, | |
3454 | <structfield>get</structfield> and | |
3455 | <structfield>put</structfield> callbacks, you can pass a value | |
3456 | through this field. If several small numbers are necessary, you can | |
3457 | combine them in bitwise. Or, it's possible to give a pointer | |
3458 | (casted to unsigned long) of some record to this field, too. | |
3459 | </para> | |
3460 | ||
3461 | <para> | |
3462 | The other three are | |
3463 | <link linkend="control-interface-callbacks"><citetitle> | |
3464 | callback functions</citetitle></link>. | |
3465 | </para> | |
3466 | </section> | |
3467 | ||
3468 | <section id="control-interface-control-names"> | |
3469 | <title>Control Names</title> | |
3470 | <para> | |
3471 | There are some standards for defining the control names. A | |
3472 | control is usually defined from the three parts as | |
3473 | <quote>SOURCE DIRECTION FUNCTION</quote>. | |
3474 | </para> | |
3475 | ||
3476 | <para> | |
3477 | The first, <constant>SOURCE</constant>, specifies the source | |
3478 | of the control, and is a string such as <quote>Master</quote>, | |
3479 | <quote>PCM</quote>, <quote>CD</quote> or | |
3480 | <quote>Line</quote>. There are many pre-defined sources. | |
3481 | </para> | |
3482 | ||
3483 | <para> | |
3484 | The second, <constant>DIRECTION</constant>, is one of the | |
3485 | following strings according to the direction of the control: | |
3486 | <quote>Playback</quote>, <quote>Capture</quote>, <quote>Bypass | |
3487 | Playback</quote> and <quote>Bypass Capture</quote>. Or, it can | |
3488 | be omitted, meaning both playback and capture directions. | |
3489 | </para> | |
3490 | ||
3491 | <para> | |
3492 | The third, <constant>FUNCTION</constant>, is one of the | |
3493 | following strings according to the function of the control: | |
3494 | <quote>Switch</quote>, <quote>Volume</quote> and | |
3495 | <quote>Route</quote>. | |
3496 | </para> | |
3497 | ||
3498 | <para> | |
3499 | The example of control names are, thus, <quote>Master Capture | |
3500 | Switch</quote> or <quote>PCM Playback Volume</quote>. | |
3501 | </para> | |
3502 | ||
3503 | <para> | |
3504 | There are some exceptions: | |
3505 | </para> | |
3506 | ||
3507 | <section id="control-interface-control-names-global"> | |
3508 | <title>Global capture and playback</title> | |
3509 | <para> | |
3510 | <quote>Capture Source</quote>, <quote>Capture Switch</quote> | |
3511 | and <quote>Capture Volume</quote> are used for the global | |
3512 | capture (input) source, switch and volume. Similarly, | |
3513 | <quote>Playback Switch</quote> and <quote>Playback | |
3514 | Volume</quote> are used for the global output gain switch and | |
3515 | volume. | |
3516 | </para> | |
3517 | </section> | |
3518 | ||
3519 | <section id="control-interface-control-names-tone"> | |
3520 | <title>Tone-controls</title> | |
3521 | <para> | |
3522 | tone-control switch and volumes are specified like | |
3523 | <quote>Tone Control - XXX</quote>, e.g. <quote>Tone Control - | |
3524 | Switch</quote>, <quote>Tone Control - Bass</quote>, | |
3525 | <quote>Tone Control - Center</quote>. | |
3526 | </para> | |
3527 | </section> | |
3528 | ||
3529 | <section id="control-interface-control-names-3d"> | |
3530 | <title>3D controls</title> | |
3531 | <para> | |
3532 | 3D-control switches and volumes are specified like <quote>3D | |
3533 | Control - XXX</quote>, e.g. <quote>3D Control - | |
3534 | Switch</quote>, <quote>3D Control - Center</quote>, <quote>3D | |
3535 | Control - Space</quote>. | |
3536 | </para> | |
3537 | </section> | |
3538 | ||
3539 | <section id="control-interface-control-names-mic"> | |
3540 | <title>Mic boost</title> | |
3541 | <para> | |
3542 | Mic-boost switch is set as <quote>Mic Boost</quote> or | |
3543 | <quote>Mic Boost (6dB)</quote>. | |
3544 | </para> | |
3545 | ||
3546 | <para> | |
3547 | More precise information can be found in | |
3548 | <filename>Documentation/sound/alsa/ControlNames.txt</filename>. | |
3549 | </para> | |
3550 | </section> | |
3551 | </section> | |
3552 | ||
3553 | <section id="control-interface-access-flags"> | |
3554 | <title>Access Flags</title> | |
3555 | ||
3556 | <para> | |
3557 | The access flag is the bit-flags which specifies the access type | |
3558 | of the given control. The default access type is | |
3559 | <constant>SNDRV_CTL_ELEM_ACCESS_READWRITE</constant>, | |
3560 | which means both read and write are allowed to this control. | |
3561 | When the access flag is omitted (i.e. = 0), it is | |
3562 | regarded as <constant>READWRITE</constant> access as default. | |
3563 | </para> | |
3564 | ||
3565 | <para> | |
3566 | When the control is read-only, pass | |
3567 | <constant>SNDRV_CTL_ELEM_ACCESS_READ</constant> instead. | |
3568 | In this case, you don't have to define | |
3569 | <structfield>put</structfield> callback. | |
3570 | Similarly, when the control is write-only (although it's a rare | |
3571 | case), you can use <constant>WRITE</constant> flag instead, and | |
3572 | you don't need <structfield>get</structfield> callback. | |
3573 | </para> | |
3574 | ||
3575 | <para> | |
3576 | If the control value changes frequently (e.g. the VU meter), | |
3577 | <constant>VOLATILE</constant> flag should be given. This means | |
3578 | that the control may be changed without | |
3579 | <link linkend="control-interface-change-notification"><citetitle> | |
3580 | notification</citetitle></link>. Applications should poll such | |
3581 | a control constantly. | |
3582 | </para> | |
3583 | ||
3584 | <para> | |
3585 | When the control is inactive, set | |
3586 | <constant>INACTIVE</constant> flag, too. | |
3587 | There are <constant>LOCK</constant> and | |
3588 | <constant>OWNER</constant> flags for changing the write | |
3589 | permissions. | |
3590 | </para> | |
3591 | ||
3592 | </section> | |
3593 | ||
3594 | <section id="control-interface-callbacks"> | |
3595 | <title>Callbacks</title> | |
3596 | ||
3597 | <section id="control-interface-callbacks-info"> | |
3598 | <title>info callback</title> | |
3599 | <para> | |
3600 | The <structfield>info</structfield> callback is used to get | |
3601 | the detailed information of this control. This must store the | |
446ab5f5 | 3602 | values of the given struct <structname>snd_ctl_elem_info</structname> |
1da177e4 LT |
3603 | object. For example, for a boolean control with a single |
3604 | element will be: | |
3605 | ||
3606 | <example> | |
3607 | <title>Example of info callback</title> | |
3608 | <programlisting> | |
3609 | <![CDATA[ | |
446ab5f5 TI |
3610 | static int snd_myctl_info(struct snd_kcontrol *kcontrol, |
3611 | struct snd_ctl_elem_info *uinfo) | |
1da177e4 LT |
3612 | { |
3613 | uinfo->type = SNDRV_CTL_ELEM_TYPE_BOOLEAN; | |
3614 | uinfo->count = 1; | |
3615 | uinfo->value.integer.min = 0; | |
3616 | uinfo->value.integer.max = 1; | |
3617 | return 0; | |
3618 | } | |
3619 | ]]> | |
3620 | </programlisting> | |
3621 | </example> | |
3622 | </para> | |
3623 | ||
3624 | <para> | |
3625 | The <structfield>type</structfield> field specifies the type | |
3626 | of the control. There are <constant>BOOLEAN</constant>, | |
3627 | <constant>INTEGER</constant>, <constant>ENUMERATED</constant>, | |
3628 | <constant>BYTES</constant>, <constant>IEC958</constant> and | |
3629 | <constant>INTEGER64</constant>. The | |
3630 | <structfield>count</structfield> field specifies the | |
3631 | number of elements in this control. For example, a stereo | |
3632 | volume would have count = 2. The | |
3633 | <structfield>value</structfield> field is a union, and | |
3634 | the values stored are depending on the type. The boolean and | |
3635 | integer are identical. | |
3636 | </para> | |
3637 | ||
3638 | <para> | |
3639 | The enumerated type is a bit different from others. You'll | |
3640 | need to set the string for the currently given item index. | |
3641 | ||
3642 | <informalexample> | |
3643 | <programlisting> | |
3644 | <![CDATA[ | |
446ab5f5 TI |
3645 | static int snd_myctl_info(struct snd_kcontrol *kcontrol, |
3646 | struct snd_ctl_elem_info *uinfo) | |
1da177e4 LT |
3647 | { |
3648 | static char *texts[4] = { | |
3649 | "First", "Second", "Third", "Fourth" | |
3650 | }; | |
3651 | uinfo->type = SNDRV_CTL_ELEM_TYPE_ENUMERATED; | |
3652 | uinfo->count = 1; | |
3653 | uinfo->value.enumerated.items = 4; | |
3654 | if (uinfo->value.enumerated.item > 3) | |
3655 | uinfo->value.enumerated.item = 3; | |
3656 | strcpy(uinfo->value.enumerated.name, | |
3657 | texts[uinfo->value.enumerated.item]); | |
3658 | return 0; | |
3659 | } | |
3660 | ]]> | |
3661 | </programlisting> | |
3662 | </informalexample> | |
3663 | </para> | |
3664 | </section> | |
3665 | ||
3666 | <section id="control-interface-callbacks-get"> | |
3667 | <title>get callback</title> | |
3668 | ||
3669 | <para> | |
3670 | This callback is used to read the current value of the | |
3671 | control and to return to the user-space. | |
3672 | </para> | |
3673 | ||
3674 | <para> | |
3675 | For example, | |
3676 | ||
3677 | <example> | |
3678 | <title>Example of get callback</title> | |
3679 | <programlisting> | |
3680 | <![CDATA[ | |
446ab5f5 TI |
3681 | static int snd_myctl_get(struct snd_kcontrol *kcontrol, |
3682 | struct snd_ctl_elem_value *ucontrol) | |
1da177e4 | 3683 | { |
446ab5f5 | 3684 | struct mychip *chip = snd_kcontrol_chip(kcontrol); |
1da177e4 LT |
3685 | ucontrol->value.integer.value[0] = get_some_value(chip); |
3686 | return 0; | |
3687 | } | |
3688 | ]]> | |
3689 | </programlisting> | |
3690 | </example> | |
3691 | </para> | |
3692 | ||
1da177e4 LT |
3693 | <para> |
3694 | The <structfield>value</structfield> field is depending on | |
3695 | the type of control as well as on info callback. For example, | |
3696 | the sb driver uses this field to store the register offset, | |
3697 | the bit-shift and the bit-mask. The | |
3698 | <structfield>private_value</structfield> is set like | |
3699 | <informalexample> | |
3700 | <programlisting> | |
3701 | <![CDATA[ | |
3702 | .private_value = reg | (shift << 16) | (mask << 24) | |
3703 | ]]> | |
3704 | </programlisting> | |
3705 | </informalexample> | |
3706 | and is retrieved in callbacks like | |
3707 | <informalexample> | |
3708 | <programlisting> | |
3709 | <![CDATA[ | |
446ab5f5 TI |
3710 | static int snd_sbmixer_get_single(struct snd_kcontrol *kcontrol, |
3711 | struct snd_ctl_elem_value *ucontrol) | |
1da177e4 LT |
3712 | { |
3713 | int reg = kcontrol->private_value & 0xff; | |
3714 | int shift = (kcontrol->private_value >> 16) & 0xff; | |
3715 | int mask = (kcontrol->private_value >> 24) & 0xff; | |
3716 | .... | |
3717 | } | |
3718 | ]]> | |
3719 | </programlisting> | |
3720 | </informalexample> | |
3721 | </para> | |
3722 | ||
3723 | <para> | |
3724 | In <structfield>get</structfield> callback, you have to fill all the elements if the | |
3725 | control has more than one elements, | |
3726 | i.e. <structfield>count</structfield> > 1. | |
3727 | In the example above, we filled only one element | |
3728 | (<structfield>value.integer.value[0]</structfield>) since it's | |
3729 | assumed as <structfield>count</structfield> = 1. | |
3730 | </para> | |
3731 | </section> | |
3732 | ||
3733 | <section id="control-interface-callbacks-put"> | |
3734 | <title>put callback</title> | |
3735 | ||
3736 | <para> | |
3737 | This callback is used to write a value from the user-space. | |
3738 | </para> | |
3739 | ||
3740 | <para> | |
3741 | For example, | |
3742 | ||
3743 | <example> | |
3744 | <title>Example of put callback</title> | |
3745 | <programlisting> | |
3746 | <![CDATA[ | |
446ab5f5 TI |
3747 | static int snd_myctl_put(struct snd_kcontrol *kcontrol, |
3748 | struct snd_ctl_elem_value *ucontrol) | |
1da177e4 | 3749 | { |
446ab5f5 | 3750 | struct mychip *chip = snd_kcontrol_chip(kcontrol); |
1da177e4 LT |
3751 | int changed = 0; |
3752 | if (chip->current_value != | |
3753 | ucontrol->value.integer.value[0]) { | |
3754 | change_current_value(chip, | |
3755 | ucontrol->value.integer.value[0]); | |
3756 | changed = 1; | |
3757 | } | |
3758 | return changed; | |
3759 | } | |
3760 | ]]> | |
3761 | </programlisting> | |
3762 | </example> | |
3763 | ||
3764 | As seen above, you have to return 1 if the value is | |
3765 | changed. If the value is not changed, return 0 instead. | |
3766 | If any fatal error happens, return a negative error code as | |
3767 | usual. | |
3768 | </para> | |
3769 | ||
3770 | <para> | |
3771 | Like <structfield>get</structfield> callback, | |
3772 | when the control has more than one elements, | |
3773 | all elemehts must be evaluated in this callback, too. | |
3774 | </para> | |
3775 | </section> | |
3776 | ||
3777 | <section id="control-interface-callbacks-all"> | |
3778 | <title>Callbacks are not atomic</title> | |
3779 | <para> | |
3780 | All these three callbacks are basically not atomic. | |
3781 | </para> | |
3782 | </section> | |
3783 | </section> | |
3784 | ||
3785 | <section id="control-interface-constructor"> | |
3786 | <title>Constructor</title> | |
3787 | <para> | |
3788 | When everything is ready, finally we can create a new | |
3789 | control. For creating a control, there are two functions to be | |
3790 | called, <function>snd_ctl_new1()</function> and | |
3791 | <function>snd_ctl_add()</function>. | |
3792 | </para> | |
3793 | ||
3794 | <para> | |
3795 | In the simplest way, you can do like this: | |
3796 | ||
3797 | <informalexample> | |
3798 | <programlisting> | |
3799 | <![CDATA[ | |
3800 | if ((err = snd_ctl_add(card, snd_ctl_new1(&my_control, chip))) < 0) | |
3801 | return err; | |
3802 | ]]> | |
3803 | </programlisting> | |
3804 | </informalexample> | |
3805 | ||
3806 | where <parameter>my_control</parameter> is the | |
446ab5f5 | 3807 | struct <structname>snd_kcontrol_new</structname> object defined above, and chip |
1da177e4 LT |
3808 | is the object pointer to be passed to |
3809 | kcontrol->private_data | |
3810 | which can be referred in callbacks. | |
3811 | </para> | |
3812 | ||
3813 | <para> | |
3814 | <function>snd_ctl_new1()</function> allocates a new | |
446ab5f5 | 3815 | <structname>snd_kcontrol</structname> instance (that's why the definition |
1da177e4 LT |
3816 | of <parameter>my_control</parameter> can be with |
3817 | <parameter>__devinitdata</parameter> | |
3818 | prefix), and <function>snd_ctl_add</function> assigns the given | |
3819 | control component to the card. | |
3820 | </para> | |
3821 | </section> | |
3822 | ||
3823 | <section id="control-interface-change-notification"> | |
3824 | <title>Change Notification</title> | |
3825 | <para> | |
3826 | If you need to change and update a control in the interrupt | |
3827 | routine, you can call <function>snd_ctl_notify()</function>. For | |
3828 | example, | |
3829 | ||
3830 | <informalexample> | |
3831 | <programlisting> | |
3832 | <![CDATA[ | |
3833 | snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_VALUE, id_pointer); | |
3834 | ]]> | |
3835 | </programlisting> | |
3836 | </informalexample> | |
3837 | ||
3838 | This function takes the card pointer, the event-mask, and the | |
3839 | control id pointer for the notification. The event-mask | |
3840 | specifies the types of notification, for example, in the above | |
3841 | example, the change of control values is notified. | |
446ab5f5 | 3842 | The id pointer is the pointer of struct <structname>snd_ctl_elem_id</structname> |
1da177e4 LT |
3843 | to be notified. |
3844 | You can find some examples in <filename>es1938.c</filename> or | |
3845 | <filename>es1968.c</filename> for hardware volume interrupts. | |
3846 | </para> | |
3847 | </section> | |
3848 | ||
3849 | </chapter> | |
3850 | ||
3851 | ||
3852 | <!-- ****************************************************** --> | |
3853 | <!-- API for AC97 Codec --> | |
3854 | <!-- ****************************************************** --> | |
3855 | <chapter id="api-ac97"> | |
3856 | <title>API for AC97 Codec</title> | |
3857 | ||
3858 | <section> | |
3859 | <title>General</title> | |
3860 | <para> | |
3861 | The ALSA AC97 codec layer is a well-defined one, and you don't | |
3862 | have to write many codes to control it. Only low-level control | |
3863 | routines are necessary. The AC97 codec API is defined in | |
3864 | <filename><sound/ac97_codec.h></filename>. | |
3865 | </para> | |
3866 | </section> | |
3867 | ||
3868 | <section id="api-ac97-example"> | |
3869 | <title>Full Code Example</title> | |
3870 | <para> | |
3871 | <example> | |
3872 | <title>Example of AC97 Interface</title> | |
3873 | <programlisting> | |
3874 | <![CDATA[ | |
446ab5f5 | 3875 | struct mychip { |
1da177e4 | 3876 | .... |
446ab5f5 | 3877 | struct snd_ac97 *ac97; |
1da177e4 LT |
3878 | .... |
3879 | }; | |
3880 | ||
446ab5f5 | 3881 | static unsigned short snd_mychip_ac97_read(struct snd_ac97 *ac97, |
1da177e4 LT |
3882 | unsigned short reg) |
3883 | { | |
446ab5f5 | 3884 | struct mychip *chip = ac97->private_data; |
1da177e4 LT |
3885 | .... |
3886 | // read a register value here from the codec | |
3887 | return the_register_value; | |
3888 | } | |
3889 | ||
446ab5f5 | 3890 | static void snd_mychip_ac97_write(struct snd_ac97 *ac97, |
1da177e4 LT |
3891 | unsigned short reg, unsigned short val) |
3892 | { | |
446ab5f5 | 3893 | struct mychip *chip = ac97->private_data; |
1da177e4 LT |
3894 | .... |
3895 | // write the given register value to the codec | |
3896 | } | |
3897 | ||
446ab5f5 | 3898 | static int snd_mychip_ac97(struct mychip *chip) |
1da177e4 | 3899 | { |
446ab5f5 TI |
3900 | struct snd_ac97_bus *bus; |
3901 | struct snd_ac97_template ac97; | |
1da177e4 | 3902 | int err; |
446ab5f5 | 3903 | static struct snd_ac97_bus_ops ops = { |
1da177e4 LT |
3904 | .write = snd_mychip_ac97_write, |
3905 | .read = snd_mychip_ac97_read, | |
3906 | }; | |
3907 | ||
3908 | if ((err = snd_ac97_bus(chip->card, 0, &ops, NULL, &bus)) < 0) | |
3909 | return err; | |
3910 | memset(&ac97, 0, sizeof(ac97)); | |
3911 | ac97.private_data = chip; | |
3912 | return snd_ac97_mixer(bus, &ac97, &chip->ac97); | |
3913 | } | |
3914 | ||
3915 | ]]> | |
3916 | </programlisting> | |
3917 | </example> | |
3918 | </para> | |
3919 | </section> | |
3920 | ||
3921 | <section id="api-ac97-constructor"> | |
3922 | <title>Constructor</title> | |
3923 | <para> | |
3924 | For creating an ac97 instance, first call <function>snd_ac97_bus</function> | |
3925 | with an <type>ac97_bus_ops_t</type> record with callback functions. | |
3926 | ||
3927 | <informalexample> | |
3928 | <programlisting> | |
3929 | <![CDATA[ | |
446ab5f5 TI |
3930 | struct snd_ac97_bus *bus; |
3931 | static struct snd_ac97_bus_ops ops = { | |
1da177e4 LT |
3932 | .write = snd_mychip_ac97_write, |
3933 | .read = snd_mychip_ac97_read, | |
3934 | }; | |
3935 | ||
3936 | snd_ac97_bus(card, 0, &ops, NULL, &pbus); | |
3937 | ]]> | |
3938 | </programlisting> | |
3939 | </informalexample> | |
3940 | ||
3941 | The bus record is shared among all belonging ac97 instances. | |
3942 | </para> | |
3943 | ||
3944 | <para> | |
446ab5f5 TI |
3945 | And then call <function>snd_ac97_mixer()</function> with an |
3946 | struct <structname>snd_ac97_template</structname> | |
1da177e4 LT |
3947 | record together with the bus pointer created above. |
3948 | ||
3949 | <informalexample> | |
3950 | <programlisting> | |
3951 | <![CDATA[ | |
446ab5f5 | 3952 | struct snd_ac97_template ac97; |
1da177e4 LT |
3953 | int err; |
3954 | ||
3955 | memset(&ac97, 0, sizeof(ac97)); | |
3956 | ac97.private_data = chip; | |
3957 | snd_ac97_mixer(bus, &ac97, &chip->ac97); | |
3958 | ]]> | |
3959 | </programlisting> | |
3960 | </informalexample> | |
3961 | ||
3962 | where chip->ac97 is the pointer of a newly created | |
3963 | <type>ac97_t</type> instance. | |
3964 | In this case, the chip pointer is set as the private data, so that | |
3965 | the read/write callback functions can refer to this chip instance. | |
3966 | This instance is not necessarily stored in the chip | |
3967 | record. When you need to change the register values from the | |
3968 | driver, or need the suspend/resume of ac97 codecs, keep this | |
3969 | pointer to pass to the corresponding functions. | |
3970 | </para> | |
3971 | </section> | |
3972 | ||
3973 | <section id="api-ac97-callbacks"> | |
3974 | <title>Callbacks</title> | |
3975 | <para> | |
3976 | The standard callbacks are <structfield>read</structfield> and | |
3977 | <structfield>write</structfield>. Obviously they | |
3978 | correspond to the functions for read and write accesses to the | |
3979 | hardware low-level codes. | |
3980 | </para> | |
3981 | ||
3982 | <para> | |
3983 | The <structfield>read</structfield> callback returns the | |
3984 | register value specified in the argument. | |
3985 | ||
3986 | <informalexample> | |
3987 | <programlisting> | |
3988 | <![CDATA[ | |
446ab5f5 | 3989 | static unsigned short snd_mychip_ac97_read(struct snd_ac97 *ac97, |
1da177e4 LT |
3990 | unsigned short reg) |
3991 | { | |
446ab5f5 | 3992 | struct mychip *chip = ac97->private_data; |
1da177e4 LT |
3993 | .... |
3994 | return the_register_value; | |
3995 | } | |
3996 | ]]> | |
3997 | </programlisting> | |
3998 | </informalexample> | |
3999 | ||
4000 | Here, the chip can be cast from ac97->private_data. | |
4001 | </para> | |
4002 | ||
4003 | <para> | |
4004 | Meanwhile, the <structfield>write</structfield> callback is | |
4005 | used to set the register value. | |
4006 | ||
4007 | <informalexample> | |
4008 | <programlisting> | |
4009 | <![CDATA[ | |
446ab5f5 | 4010 | static void snd_mychip_ac97_write(struct snd_ac97 *ac97, |
1da177e4 LT |
4011 | unsigned short reg, unsigned short val) |
4012 | ]]> | |
4013 | </programlisting> | |
4014 | </informalexample> | |
4015 | </para> | |
4016 | ||
4017 | <para> | |
4018 | These callbacks are non-atomic like the callbacks of control API. | |
4019 | </para> | |
4020 | ||
4021 | <para> | |
4022 | There are also other callbacks: | |
4023 | <structfield>reset</structfield>, | |
4024 | <structfield>wait</structfield> and | |
4025 | <structfield>init</structfield>. | |
4026 | </para> | |
4027 | ||
4028 | <para> | |
4029 | The <structfield>reset</structfield> callback is used to reset | |
4030 | the codec. If the chip requires a special way of reset, you can | |
4031 | define this callback. | |
4032 | </para> | |
4033 | ||
4034 | <para> | |
4035 | The <structfield>wait</structfield> callback is used for a | |
4036 | certain wait at the standard initialization of the codec. If the | |
4037 | chip requires the extra wait-time, define this callback. | |
4038 | </para> | |
4039 | ||
4040 | <para> | |
4041 | The <structfield>init</structfield> callback is used for | |
4042 | additional initialization of the codec. | |
4043 | </para> | |
4044 | </section> | |
4045 | ||
4046 | <section id="api-ac97-updating-registers"> | |
4047 | <title>Updating Registers in The Driver</title> | |
4048 | <para> | |
4049 | If you need to access to the codec from the driver, you can | |
4050 | call the following functions: | |
4051 | <function>snd_ac97_write()</function>, | |
4052 | <function>snd_ac97_read()</function>, | |
4053 | <function>snd_ac97_update()</function> and | |
4054 | <function>snd_ac97_update_bits()</function>. | |
4055 | </para> | |
4056 | ||
4057 | <para> | |
4058 | Both <function>snd_ac97_write()</function> and | |
4059 | <function>snd_ac97_update()</function> functions are used to | |
4060 | set a value to the given register | |
4061 | (<constant>AC97_XXX</constant>). The difference between them is | |
4062 | that <function>snd_ac97_update()</function> doesn't write a | |
4063 | value if the given value has been already set, while | |
4064 | <function>snd_ac97_write()</function> always rewrites the | |
4065 | value. | |
4066 | ||
4067 | <informalexample> | |
4068 | <programlisting> | |
4069 | <![CDATA[ | |
4070 | snd_ac97_write(ac97, AC97_MASTER, 0x8080); | |
4071 | snd_ac97_update(ac97, AC97_MASTER, 0x8080); | |
4072 | ]]> | |
4073 | </programlisting> | |
4074 | </informalexample> | |
4075 | </para> | |
4076 | ||
4077 | <para> | |
4078 | <function>snd_ac97_read()</function> is used to read the value | |
4079 | of the given register. For example, | |
4080 | ||
4081 | <informalexample> | |
4082 | <programlisting> | |
4083 | <![CDATA[ | |
4084 | value = snd_ac97_read(ac97, AC97_MASTER); | |
4085 | ]]> | |
4086 | </programlisting> | |
4087 | </informalexample> | |
4088 | </para> | |
4089 | ||
4090 | <para> | |
4091 | <function>snd_ac97_update_bits()</function> is used to update | |
4092 | some bits of the given register. | |
4093 | ||
4094 | <informalexample> | |
4095 | <programlisting> | |
4096 | <![CDATA[ | |
4097 | snd_ac97_update_bits(ac97, reg, mask, value); | |
4098 | ]]> | |
4099 | </programlisting> | |
4100 | </informalexample> | |
4101 | </para> | |
4102 | ||
4103 | <para> | |
4104 | Also, there is a function to change the sample rate (of a | |
4105 | certain register such as | |
4106 | <constant>AC97_PCM_FRONT_DAC_RATE</constant>) when VRA or | |
4107 | DRA is supported by the codec: | |
4108 | <function>snd_ac97_set_rate()</function>. | |
4109 | ||
4110 | <informalexample> | |
4111 | <programlisting> | |
4112 | <![CDATA[ | |
4113 | snd_ac97_set_rate(ac97, AC97_PCM_FRONT_DAC_RATE, 44100); | |
4114 | ]]> | |
4115 | </programlisting> | |
4116 | </informalexample> | |
4117 | </para> | |
4118 | ||
4119 | <para> | |
4120 | The following registers are available for setting the rate: | |
4121 | <constant>AC97_PCM_MIC_ADC_RATE</constant>, | |
4122 | <constant>AC97_PCM_FRONT_DAC_RATE</constant>, | |
4123 | <constant>AC97_PCM_LR_ADC_RATE</constant>, | |
4124 | <constant>AC97_SPDIF</constant>. When the | |
4125 | <constant>AC97_SPDIF</constant> is specified, the register is | |
4126 | not really changed but the corresponding IEC958 status bits will | |
4127 | be updated. | |
4128 | </para> | |
4129 | </section> | |
4130 | ||
4131 | <section id="api-ac97-clock-adjustment"> | |
4132 | <title>Clock Adjustment</title> | |
4133 | <para> | |
4134 | On some chip, the clock of the codec isn't 48000 but using a | |
4135 | PCI clock (to save a quartz!). In this case, change the field | |
4136 | bus->clock to the corresponding | |
4137 | value. For example, intel8x0 | |
4138 | and es1968 drivers have the auto-measurement function of the | |
4139 | clock. | |
4140 | </para> | |
4141 | </section> | |
4142 | ||
4143 | <section id="api-ac97-proc-files"> | |
4144 | <title>Proc Files</title> | |
4145 | <para> | |
4146 | The ALSA AC97 interface will create a proc file such as | |
4147 | <filename>/proc/asound/card0/codec97#0/ac97#0-0</filename> and | |
4148 | <filename>ac97#0-0+regs</filename>. You can refer to these files to | |
4149 | see the current status and registers of the codec. | |
4150 | </para> | |
4151 | </section> | |
4152 | ||
4153 | <section id="api-ac97-multiple-codecs"> | |
4154 | <title>Multiple Codecs</title> | |
4155 | <para> | |
4156 | When there are several codecs on the same card, you need to | |
446ab5f5 | 4157 | call <function>snd_ac97_mixer()</function> multiple times with |
1da177e4 LT |
4158 | ac97.num=1 or greater. The <structfield>num</structfield> field |
4159 | specifies the codec | |
4160 | number. | |
4161 | </para> | |
4162 | ||
4163 | <para> | |
4164 | If you have set up multiple codecs, you need to either write | |
4165 | different callbacks for each codec or check | |
4166 | ac97->num in the | |
4167 | callback routines. | |
4168 | </para> | |
4169 | </section> | |
4170 | ||
4171 | </chapter> | |
4172 | ||
4173 | ||
4174 | <!-- ****************************************************** --> | |
4175 | <!-- MIDI (MPU401-UART) Interface --> | |
4176 | <!-- ****************************************************** --> | |
4177 | <chapter id="midi-interface"> | |
4178 | <title>MIDI (MPU401-UART) Interface</title> | |
4179 | ||
4180 | <section id="midi-interface-general"> | |
4181 | <title>General</title> | |
4182 | <para> | |
4183 | Many soundcards have built-in MIDI (MPU401-UART) | |
4184 | interfaces. When the soundcard supports the standard MPU401-UART | |
4185 | interface, most likely you can use the ALSA MPU401-UART API. The | |
4186 | MPU401-UART API is defined in | |
4187 | <filename><sound/mpu401.h></filename>. | |
4188 | </para> | |
4189 | ||
4190 | <para> | |
4191 | Some soundchips have similar but a little bit different | |
4192 | implementation of mpu401 stuff. For example, emu10k1 has its own | |
4193 | mpu401 routines. | |
4194 | </para> | |
4195 | </section> | |
4196 | ||
4197 | <section id="midi-interface-constructor"> | |
4198 | <title>Constructor</title> | |
4199 | <para> | |
4200 | For creating a rawmidi object, call | |
4201 | <function>snd_mpu401_uart_new()</function>. | |
4202 | ||
4203 | <informalexample> | |
4204 | <programlisting> | |
4205 | <![CDATA[ | |
446ab5f5 | 4206 | struct snd_rawmidi *rmidi; |
302e4c2f | 4207 | snd_mpu401_uart_new(card, 0, MPU401_HW_MPU401, port, info_flags, |
1da177e4 LT |
4208 | irq, irq_flags, &rmidi); |
4209 | ]]> | |
4210 | </programlisting> | |
4211 | </informalexample> | |
4212 | </para> | |
4213 | ||
4214 | <para> | |
4215 | The first argument is the card pointer, and the second is the | |
4216 | index of this component. You can create up to 8 rawmidi | |
4217 | devices. | |
4218 | </para> | |
4219 | ||
4220 | <para> | |
4221 | The third argument is the type of the hardware, | |
4222 | <constant>MPU401_HW_XXX</constant>. If it's not a special one, | |
4223 | you can use <constant>MPU401_HW_MPU401</constant>. | |
4224 | </para> | |
4225 | ||
4226 | <para> | |
4227 | The 4th argument is the i/o port address. Many | |
4228 | backward-compatible MPU401 has an i/o port such as 0x330. Or, it | |
4229 | might be a part of its own PCI i/o region. It depends on the | |
4230 | chip design. | |
4231 | </para> | |
4232 | ||
4233 | <para> | |
302e4c2f | 4234 | The 5th argument is bitflags for additional information. |
1da177e4 LT |
4235 | When the i/o port address above is a part of the PCI i/o |
4236 | region, the MPU401 i/o port might have been already allocated | |
302e4c2f TI |
4237 | (reserved) by the driver itself. In such a case, pass a bit flag |
4238 | <constant>MPU401_INFO_INTEGRATED</constant>, | |
1da177e4 LT |
4239 | and |
4240 | the mpu401-uart layer will allocate the i/o ports by itself. | |
4241 | </para> | |
4242 | ||
302e4c2f TI |
4243 | <para> |
4244 | When the controller supports only the input or output MIDI stream, | |
4245 | pass <constant>MPU401_INFO_INPUT</constant> or | |
4246 | <constant>MPU401_INFO_OUTPUT</constant> bitflag, respectively. | |
4247 | Then the rawmidi instance is created as a single stream. | |
4248 | </para> | |
4249 | ||
4250 | <para> | |
4251 | <constant>MPU401_INFO_MMIO</constant> bitflag is used to change | |
4252 | the access method to MMIO (via readb and writeb) instead of | |
4253 | iob and outb. In this case, you have to pass the iomapped address | |
4254 | to <function>snd_mpu401_uart_new()</function>. | |
4255 | </para> | |
4256 | ||
4257 | <para> | |
4258 | When <constant>MPU401_INFO_TX_IRQ</constant> is set, the output | |
4259 | stream isn't checked in the default interrupt handler. The driver | |
4260 | needs to call <function>snd_mpu401_uart_interrupt_tx()</function> | |
4261 | by itself to start processing the output stream in irq handler. | |
4262 | </para> | |
4263 | ||
1da177e4 LT |
4264 | <para> |
4265 | Usually, the port address corresponds to the command port and | |
4266 | port + 1 corresponds to the data port. If not, you may change | |
4267 | the <structfield>cport</structfield> field of | |
446ab5f5 TI |
4268 | struct <structname>snd_mpu401</structname> manually |
4269 | afterward. However, <structname>snd_mpu401</structname> pointer is not | |
1da177e4 LT |
4270 | returned explicitly by |
4271 | <function>snd_mpu401_uart_new()</function>. You need to cast | |
4272 | rmidi->private_data to | |
446ab5f5 | 4273 | <structname>snd_mpu401</structname> explicitly, |
1da177e4 LT |
4274 | |
4275 | <informalexample> | |
4276 | <programlisting> | |
4277 | <![CDATA[ | |
446ab5f5 | 4278 | struct snd_mpu401 *mpu; |
1da177e4 LT |
4279 | mpu = rmidi->private_data; |
4280 | ]]> | |
4281 | </programlisting> | |
4282 | </informalexample> | |
4283 | ||
4284 | and reset the cport as you like: | |
4285 | ||
4286 | <informalexample> | |
4287 | <programlisting> | |
4288 | <![CDATA[ | |
4289 | mpu->cport = my_own_control_port; | |
4290 | ]]> | |
4291 | </programlisting> | |
4292 | </informalexample> | |
4293 | </para> | |
4294 | ||
4295 | <para> | |
4296 | The 6th argument specifies the irq number for UART. If the irq | |
4297 | is already allocated, pass 0 to the 7th argument | |
4298 | (<parameter>irq_flags</parameter>). Otherwise, pass the flags | |
4299 | for irq allocation | |
4300 | (<constant>SA_XXX</constant> bits) to it, and the irq will be | |
4301 | reserved by the mpu401-uart layer. If the card doesn't generates | |
4302 | UART interrupts, pass -1 as the irq number. Then a timer | |
4303 | interrupt will be invoked for polling. | |
4304 | </para> | |
4305 | </section> | |
4306 | ||
4307 | <section id="midi-interface-interrupt-handler"> | |
4308 | <title>Interrupt Handler</title> | |
4309 | <para> | |
4310 | When the interrupt is allocated in | |
4311 | <function>snd_mpu401_uart_new()</function>, the private | |
4312 | interrupt handler is used, hence you don't have to do nothing | |
4313 | else than creating the mpu401 stuff. Otherwise, you have to call | |
4314 | <function>snd_mpu401_uart_interrupt()</function> explicitly when | |
4315 | a UART interrupt is invoked and checked in your own interrupt | |
4316 | handler. | |
4317 | </para> | |
4318 | ||
4319 | <para> | |
4320 | In this case, you need to pass the private_data of the | |
4321 | returned rawmidi object from | |
4322 | <function>snd_mpu401_uart_new()</function> as the second | |
4323 | argument of <function>snd_mpu401_uart_interrupt()</function>. | |
4324 | ||
4325 | <informalexample> | |
4326 | <programlisting> | |
4327 | <![CDATA[ | |
4328 | snd_mpu401_uart_interrupt(irq, rmidi->private_data, regs); | |
4329 | ]]> | |
4330 | </programlisting> | |
4331 | </informalexample> | |
4332 | </para> | |
4333 | </section> | |
4334 | ||
4335 | </chapter> | |
4336 | ||
4337 | ||
4338 | <!-- ****************************************************** --> | |
4339 | <!-- RawMIDI Interface --> | |
4340 | <!-- ****************************************************** --> | |
4341 | <chapter id="rawmidi-interface"> | |
4342 | <title>RawMIDI Interface</title> | |
4343 | ||
4344 | <section id="rawmidi-interface-overview"> | |
4345 | <title>Overview</title> | |
4346 | ||
4347 | <para> | |
4348 | The raw MIDI interface is used for hardware MIDI ports that can | |
4349 | be accessed as a byte stream. It is not used for synthesizer | |
4350 | chips that do not directly understand MIDI. | |
4351 | </para> | |
4352 | ||
4353 | <para> | |
4354 | ALSA handles file and buffer management. All you have to do is | |
4355 | to write some code to move data between the buffer and the | |
4356 | hardware. | |
4357 | </para> | |
4358 | ||
4359 | <para> | |
4360 | The rawmidi API is defined in | |
4361 | <filename><sound/rawmidi.h></filename>. | |
4362 | </para> | |
4363 | </section> | |
4364 | ||
4365 | <section id="rawmidi-interface-constructor"> | |
4366 | <title>Constructor</title> | |
4367 | ||
4368 | <para> | |
4369 | To create a rawmidi device, call the | |
4370 | <function>snd_rawmidi_new</function> function: | |
4371 | <informalexample> | |
4372 | <programlisting> | |
4373 | <![CDATA[ | |
446ab5f5 | 4374 | struct snd_rawmidi *rmidi; |
1da177e4 LT |
4375 | err = snd_rawmidi_new(chip->card, "MyMIDI", 0, outs, ins, &rmidi); |
4376 | if (err < 0) | |
4377 | return err; | |
4378 | rmidi->private_data = chip; | |
4379 | strcpy(rmidi->name, "My MIDI"); | |
4380 | rmidi->info_flags = SNDRV_RAWMIDI_INFO_OUTPUT | | |
4381 | SNDRV_RAWMIDI_INFO_INPUT | | |
4382 | SNDRV_RAWMIDI_INFO_DUPLEX; | |
4383 | ]]> | |
4384 | </programlisting> | |
4385 | </informalexample> | |
4386 | </para> | |
4387 | ||
4388 | <para> | |
4389 | The first argument is the card pointer, the second argument is | |
4390 | the ID string. | |
4391 | </para> | |
4392 | ||
4393 | <para> | |
4394 | The third argument is the index of this component. You can | |
4395 | create up to 8 rawmidi devices. | |
4396 | </para> | |
4397 | ||
4398 | <para> | |
4399 | The fourth and fifth arguments are the number of output and | |
4400 | input substreams, respectively, of this device. (A substream is | |
4401 | the equivalent of a MIDI port.) | |
4402 | </para> | |
4403 | ||
4404 | <para> | |
4405 | Set the <structfield>info_flags</structfield> field to specify | |
4406 | the capabilities of the device. | |
4407 | Set <constant>SNDRV_RAWMIDI_INFO_OUTPUT</constant> if there is | |
4408 | at least one output port, | |
4409 | <constant>SNDRV_RAWMIDI_INFO_INPUT</constant> if there is at | |
4410 | least one input port, | |
4411 | and <constant>SNDRV_RAWMIDI_INFO_DUPLEX</constant> if the device | |
4412 | can handle output and input at the same time. | |
4413 | </para> | |
4414 | ||
4415 | <para> | |
4416 | After the rawmidi device is created, you need to set the | |
4417 | operators (callbacks) for each substream. There are helper | |
4418 | functions to set the operators for all substream of a device: | |
4419 | <informalexample> | |
4420 | <programlisting> | |
4421 | <![CDATA[ | |
4422 | snd_rawmidi_set_ops(rmidi, SNDRV_RAWMIDI_STREAM_OUTPUT, &snd_mymidi_output_ops); | |
4423 | snd_rawmidi_set_ops(rmidi, SNDRV_RAWMIDI_STREAM_INPUT, &snd_mymidi_input_ops); | |
4424 | ]]> | |
4425 | </programlisting> | |
4426 | </informalexample> | |
4427 | </para> | |
4428 | ||
4429 | <para> | |
4430 | The operators are usually defined like this: | |
4431 | <informalexample> | |
4432 | <programlisting> | |
4433 | <![CDATA[ | |
446ab5f5 | 4434 | static struct snd_rawmidi_ops snd_mymidi_output_ops = { |
1da177e4 LT |
4435 | .open = snd_mymidi_output_open, |
4436 | .close = snd_mymidi_output_close, | |
4437 | .trigger = snd_mymidi_output_trigger, | |
4438 | }; | |
4439 | ]]> | |
4440 | </programlisting> | |
4441 | </informalexample> | |
4442 | These callbacks are explained in the <link | |
4443 | linkend="rawmidi-interface-callbacks"><citetitle>Callbacks</citetitle></link> | |
4444 | section. | |
4445 | </para> | |
4446 | ||
4447 | <para> | |
4448 | If there is more than one substream, you should give each one a | |
4449 | unique name: | |
4450 | <informalexample> | |
4451 | <programlisting> | |
4452 | <![CDATA[ | |
4453 | struct list_head *list; | |
446ab5f5 | 4454 | struct snd_rawmidi_substream *substream; |
1da177e4 | 4455 | list_for_each(list, &rmidi->streams[SNDRV_RAWMIDI_STREAM_OUTPUT].substreams) { |
446ab5f5 | 4456 | substream = list_entry(list, struct snd_rawmidi_substream, list); |
1da177e4 LT |
4457 | sprintf(substream->name, "My MIDI Port %d", substream->number + 1); |
4458 | } | |
4459 | /* same for SNDRV_RAWMIDI_STREAM_INPUT */ | |
4460 | ]]> | |
4461 | </programlisting> | |
4462 | </informalexample> | |
4463 | </para> | |
4464 | </section> | |
4465 | ||
4466 | <section id="rawmidi-interface-callbacks"> | |
4467 | <title>Callbacks</title> | |
4468 | ||
4469 | <para> | |
4470 | In all callbacks, the private data that you've set for the | |
4471 | rawmidi device can be accessed as | |
4472 | substream->rmidi->private_data. | |
4473 | <!-- <code> isn't available before DocBook 4.3 --> | |
4474 | </para> | |
4475 | ||
4476 | <para> | |
4477 | If there is more than one port, your callbacks can determine the | |
446ab5f5 | 4478 | port index from the struct snd_rawmidi_substream data passed to each |
1da177e4 LT |
4479 | callback: |
4480 | <informalexample> | |
4481 | <programlisting> | |
4482 | <![CDATA[ | |
446ab5f5 | 4483 | struct snd_rawmidi_substream *substream; |
1da177e4 LT |
4484 | int index = substream->number; |
4485 | ]]> | |
4486 | </programlisting> | |
4487 | </informalexample> | |
4488 | </para> | |
4489 | ||
4490 | <section id="rawmidi-interface-op-open"> | |
4491 | <title><function>open</function> callback</title> | |
4492 | ||
4493 | <informalexample> | |
4494 | <programlisting> | |
4495 | <![CDATA[ | |
446ab5f5 | 4496 | static int snd_xxx_open(struct snd_rawmidi_substream *substream); |
1da177e4 LT |
4497 | ]]> |
4498 | </programlisting> | |
4499 | </informalexample> | |
4500 | ||
4501 | <para> | |
4502 | This is called when a substream is opened. | |
4503 | You can initialize the hardware here, but you should not yet | |
4504 | start transmitting/receiving data. | |
4505 | </para> | |
4506 | </section> | |
4507 | ||
4508 | <section id="rawmidi-interface-op-close"> | |
4509 | <title><function>close</function> callback</title> | |
4510 | ||
4511 | <informalexample> | |
4512 | <programlisting> | |
4513 | <![CDATA[ | |
446ab5f5 | 4514 | static int snd_xxx_close(struct snd_rawmidi_substream *substream); |
1da177e4 LT |
4515 | ]]> |
4516 | </programlisting> | |
4517 | </informalexample> | |
4518 | ||
4519 | <para> | |
4520 | Guess what. | |
4521 | </para> | |
4522 | ||
4523 | <para> | |
4524 | The <function>open</function> and <function>close</function> | |
4525 | callbacks of a rawmidi device are serialized with a mutex, | |
4526 | and can sleep. | |
4527 | </para> | |
4528 | </section> | |
4529 | ||
4530 | <section id="rawmidi-interface-op-trigger-out"> | |
4531 | <title><function>trigger</function> callback for output | |
4532 | substreams</title> | |
4533 | ||
4534 | <informalexample> | |
4535 | <programlisting> | |
4536 | <![CDATA[ | |
446ab5f5 | 4537 | static void snd_xxx_output_trigger(struct snd_rawmidi_substream *substream, int up); |
1da177e4 LT |
4538 | ]]> |
4539 | </programlisting> | |
4540 | </informalexample> | |
4541 | ||
4542 | <para> | |
4543 | This is called with a nonzero <parameter>up</parameter> | |
4544 | parameter when there is some data in the substream buffer that | |
4545 | must be transmitted. | |
4546 | </para> | |
4547 | ||
4548 | <para> | |
4549 | To read data from the buffer, call | |
4550 | <function>snd_rawmidi_transmit_peek</function>. It will | |
4551 | return the number of bytes that have been read; this will be | |
4552 | less than the number of bytes requested when there is no more | |
4553 | data in the buffer. | |
4554 | After the data has been transmitted successfully, call | |
4555 | <function>snd_rawmidi_transmit_ack</function> to remove the | |
4556 | data from the substream buffer: | |
4557 | <informalexample> | |
4558 | <programlisting> | |
4559 | <![CDATA[ | |
4560 | unsigned char data; | |
4561 | while (snd_rawmidi_transmit_peek(substream, &data, 1) == 1) { | |
446ab5f5 | 4562 | if (snd_mychip_try_to_transmit(data)) |
1da177e4 LT |
4563 | snd_rawmidi_transmit_ack(substream, 1); |
4564 | else | |
4565 | break; /* hardware FIFO full */ | |
4566 | } | |
4567 | ]]> | |
4568 | </programlisting> | |
4569 | </informalexample> | |
4570 | </para> | |
4571 | ||
4572 | <para> | |
4573 | If you know beforehand that the hardware will accept data, you | |
4574 | can use the <function>snd_rawmidi_transmit</function> function | |
4575 | which reads some data and removes it from the buffer at once: | |
4576 | <informalexample> | |
4577 | <programlisting> | |
4578 | <![CDATA[ | |
446ab5f5 | 4579 | while (snd_mychip_transmit_possible()) { |
1da177e4 LT |
4580 | unsigned char data; |
4581 | if (snd_rawmidi_transmit(substream, &data, 1) != 1) | |
4582 | break; /* no more data */ | |
446ab5f5 | 4583 | snd_mychip_transmit(data); |
1da177e4 LT |
4584 | } |
4585 | ]]> | |
4586 | </programlisting> | |
4587 | </informalexample> | |
4588 | </para> | |
4589 | ||
4590 | <para> | |
4591 | If you know beforehand how many bytes you can accept, you can | |
4592 | use a buffer size greater than one with the | |
4593 | <function>snd_rawmidi_transmit*</function> functions. | |
4594 | </para> | |
4595 | ||
4596 | <para> | |
4597 | The <function>trigger</function> callback must not sleep. If | |
4598 | the hardware FIFO is full before the substream buffer has been | |
4599 | emptied, you have to continue transmitting data later, either | |
4600 | in an interrupt handler, or with a timer if the hardware | |
4601 | doesn't have a MIDI transmit interrupt. | |
4602 | </para> | |
4603 | ||
4604 | <para> | |
4605 | The <function>trigger</function> callback is called with a | |
4606 | zero <parameter>up</parameter> parameter when the transmission | |
4607 | of data should be aborted. | |
4608 | </para> | |
4609 | </section> | |
4610 | ||
4611 | <section id="rawmidi-interface-op-trigger-in"> | |
4612 | <title><function>trigger</function> callback for input | |
4613 | substreams</title> | |
4614 | ||
4615 | <informalexample> | |
4616 | <programlisting> | |
4617 | <![CDATA[ | |
446ab5f5 | 4618 | static void snd_xxx_input_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 to enable receiving data, or with a zero | |
4626 | <parameter>up</parameter> parameter do disable receiving data. | |
4627 | </para> | |
4628 | ||
4629 | <para> | |
4630 | The <function>trigger</function> callback must not sleep; the | |
4631 | actual reading of data from the device is usually done in an | |
4632 | interrupt handler. | |
4633 | </para> | |
4634 | ||
4635 | <para> | |
4636 | When data reception is enabled, your interrupt handler should | |
4637 | call <function>snd_rawmidi_receive</function> for all received | |
4638 | data: | |
4639 | <informalexample> | |
4640 | <programlisting> | |
4641 | <![CDATA[ | |
4642 | void snd_mychip_midi_interrupt(...) | |
4643 | { | |
4644 | while (mychip_midi_available()) { | |
4645 | unsigned char data; | |
4646 | data = mychip_midi_read(); | |
4647 | snd_rawmidi_receive(substream, &data, 1); | |
4648 | } | |
4649 | } | |
4650 | ]]> | |
4651 | </programlisting> | |
4652 | </informalexample> | |
4653 | </para> | |
4654 | </section> | |
4655 | ||
4656 | <section id="rawmidi-interface-op-drain"> | |
4657 | <title><function>drain</function> callback</title> | |
4658 | ||
4659 | <informalexample> | |
4660 | <programlisting> | |
4661 | <![CDATA[ | |
446ab5f5 | 4662 | static void snd_xxx_drain(struct snd_rawmidi_substream *substream); |
1da177e4 LT |
4663 | ]]> |
4664 | </programlisting> | |
4665 | </informalexample> | |
4666 | ||
4667 | <para> | |
4668 | This is only used with output substreams. This function should wait | |
4669 | until all data read from the substream buffer has been transmitted. | |
4670 | This ensures that the device can be closed and the driver unloaded | |
4671 | without losing data. | |
4672 | </para> | |
4673 | ||
4674 | <para> | |
4675 | This callback is optional. If you do not set | |
446ab5f5 | 4676 | <structfield>drain</structfield> in the struct snd_rawmidi_ops |
1da177e4 LT |
4677 | structure, ALSA will simply wait for 50 milliseconds |
4678 | instead. | |
4679 | </para> | |
4680 | </section> | |
4681 | </section> | |
4682 | ||
4683 | </chapter> | |
4684 | ||
4685 | ||
4686 | <!-- ****************************************************** --> | |
4687 | <!-- Miscellaneous Devices --> | |
4688 | <!-- ****************************************************** --> | |
4689 | <chapter id="misc-devices"> | |
4690 | <title>Miscellaneous Devices</title> | |
4691 | ||
4692 | <section id="misc-devices-opl3"> | |
4693 | <title>FM OPL3</title> | |
4694 | <para> | |
4695 | The FM OPL3 is still used on many chips (mainly for backward | |
4696 | compatibility). ALSA has a nice OPL3 FM control layer, too. The | |
4697 | OPL3 API is defined in | |
4698 | <filename><sound/opl3.h></filename>. | |
4699 | </para> | |
4700 | ||
4701 | <para> | |
4702 | FM registers can be directly accessed through direct-FM API, | |
4703 | defined in <filename><sound/asound_fm.h></filename>. In | |
4704 | ALSA native mode, FM registers are accessed through | |
4705 | Hardware-Dependant Device direct-FM extension API, whereas in | |
4706 | OSS compatible mode, FM registers can be accessed with OSS | |
4707 | direct-FM compatible API on <filename>/dev/dmfmX</filename> device. | |
4708 | </para> | |
4709 | ||
4710 | <para> | |
4711 | For creating the OPL3 component, you have two functions to | |
4712 | call. The first one is a constructor for <type>opl3_t</type> | |
4713 | instance. | |
4714 | ||
4715 | <informalexample> | |
4716 | <programlisting> | |
4717 | <![CDATA[ | |
446ab5f5 | 4718 | struct snd_opl3 *opl3; |
1da177e4 LT |
4719 | snd_opl3_create(card, lport, rport, OPL3_HW_OPL3_XXX, |
4720 | integrated, &opl3); | |
4721 | ]]> | |
4722 | </programlisting> | |
4723 | </informalexample> | |
4724 | </para> | |
4725 | ||
4726 | <para> | |
4727 | The first argument is the card pointer, the second one is the | |
4728 | left port address, and the third is the right port address. In | |
4729 | most cases, the right port is placed at the left port + 2. | |
4730 | </para> | |
4731 | ||
4732 | <para> | |
4733 | The fourth argument is the hardware type. | |
4734 | </para> | |
4735 | ||
4736 | <para> | |
4737 | When the left and right ports have been already allocated by | |
4738 | the card driver, pass non-zero to the fifth argument | |
4739 | (<parameter>integrated</parameter>). Otherwise, opl3 module will | |
4740 | allocate the specified ports by itself. | |
4741 | </para> | |
4742 | ||
4743 | <para> | |
4744 | When the accessing to the hardware requires special method | |
4745 | instead of the standard I/O access, you can create opl3 instance | |
4746 | separately with <function>snd_opl3_new()</function>. | |
4747 | ||
4748 | <informalexample> | |
4749 | <programlisting> | |
4750 | <![CDATA[ | |
446ab5f5 | 4751 | struct snd_opl3 *opl3; |
1da177e4 LT |
4752 | snd_opl3_new(card, OPL3_HW_OPL3_XXX, &opl3); |
4753 | ]]> | |
4754 | </programlisting> | |
4755 | </informalexample> | |
4756 | </para> | |
4757 | ||
4758 | <para> | |
4759 | Then set <structfield>command</structfield>, | |
4760 | <structfield>private_data</structfield> and | |
4761 | <structfield>private_free</structfield> for the private | |
4762 | access function, the private data and the destructor. | |
4763 | The l_port and r_port are not necessarily set. Only the | |
4764 | command must be set properly. You can retrieve the data | |
4765 | from opl3->private_data field. | |
4766 | </para> | |
4767 | ||
4768 | <para> | |
4769 | After creating the opl3 instance via <function>snd_opl3_new()</function>, | |
4770 | call <function>snd_opl3_init()</function> to initialize the chip to the | |
4771 | proper state. Note that <function>snd_opl3_create()</function> always | |
4772 | calls it internally. | |
4773 | </para> | |
4774 | ||
4775 | <para> | |
4776 | If the opl3 instance is created successfully, then create a | |
4777 | hwdep device for this opl3. | |
4778 | ||
4779 | <informalexample> | |
4780 | <programlisting> | |
4781 | <![CDATA[ | |
446ab5f5 | 4782 | struct snd_hwdep *opl3hwdep; |
1da177e4 LT |
4783 | snd_opl3_hwdep_new(opl3, 0, 1, &opl3hwdep); |
4784 | ]]> | |
4785 | </programlisting> | |
4786 | </informalexample> | |
4787 | </para> | |
4788 | ||
4789 | <para> | |
4790 | The first argument is the <type>opl3_t</type> instance you | |
4791 | created, and the second is the index number, usually 0. | |
4792 | </para> | |
4793 | ||
4794 | <para> | |
4795 | The third argument is the index-offset for the sequencer | |
4796 | client assigned to the OPL3 port. When there is an MPU401-UART, | |
4797 | give 1 for here (UART always takes 0). | |
4798 | </para> | |
4799 | </section> | |
4800 | ||
4801 | <section id="misc-devices-hardware-dependent"> | |
4802 | <title>Hardware-Dependent Devices</title> | |
4803 | <para> | |
4804 | Some chips need the access from the user-space for special | |
4805 | controls or for loading the micro code. In such a case, you can | |
4806 | create a hwdep (hardware-dependent) device. The hwdep API is | |
4807 | defined in <filename><sound/hwdep.h></filename>. You can | |
4808 | find examples in opl3 driver or | |
4809 | <filename>isa/sb/sb16_csp.c</filename>. | |
4810 | </para> | |
4811 | ||
4812 | <para> | |
4813 | Creation of the <type>hwdep</type> instance is done via | |
4814 | <function>snd_hwdep_new()</function>. | |
4815 | ||
4816 | <informalexample> | |
4817 | <programlisting> | |
4818 | <![CDATA[ | |
446ab5f5 | 4819 | struct snd_hwdep *hw; |
1da177e4 LT |
4820 | snd_hwdep_new(card, "My HWDEP", 0, &hw); |
4821 | ]]> | |
4822 | </programlisting> | |
4823 | </informalexample> | |
4824 | ||
4825 | where the third argument is the index number. | |
4826 | </para> | |
4827 | ||
4828 | <para> | |
4829 | You can then pass any pointer value to the | |
4830 | <parameter>private_data</parameter>. | |
4831 | If you assign a private data, you should define the | |
4832 | destructor, too. The destructor function is set to | |
4833 | <structfield>private_free</structfield> field. | |
4834 | ||
4835 | <informalexample> | |
4836 | <programlisting> | |
4837 | <![CDATA[ | |
446ab5f5 | 4838 | struct mydata *p = kmalloc(sizeof(*p), GFP_KERNEL); |
1da177e4 LT |
4839 | hw->private_data = p; |
4840 | hw->private_free = mydata_free; | |
4841 | ]]> | |
4842 | </programlisting> | |
4843 | </informalexample> | |
4844 | ||
4845 | and the implementation of destructor would be: | |
4846 | ||
4847 | <informalexample> | |
4848 | <programlisting> | |
4849 | <![CDATA[ | |
446ab5f5 | 4850 | static void mydata_free(struct snd_hwdep *hw) |
1da177e4 | 4851 | { |
446ab5f5 | 4852 | struct mydata *p = hw->private_data; |
1da177e4 LT |
4853 | kfree(p); |
4854 | } | |
4855 | ]]> | |
4856 | </programlisting> | |
4857 | </informalexample> | |
4858 | </para> | |
4859 | ||
4860 | <para> | |
4861 | The arbitrary file operations can be defined for this | |
4862 | instance. The file operators are defined in | |
4863 | <parameter>ops</parameter> table. For example, assume that | |
4864 | this chip needs an ioctl. | |
4865 | ||
4866 | <informalexample> | |
4867 | <programlisting> | |
4868 | <![CDATA[ | |
4869 | hw->ops.open = mydata_open; | |
4870 | hw->ops.ioctl = mydata_ioctl; | |
4871 | hw->ops.release = mydata_release; | |
4872 | ]]> | |
4873 | </programlisting> | |
4874 | </informalexample> | |
4875 | ||
4876 | And implement the callback functions as you like. | |
4877 | </para> | |
4878 | </section> | |
4879 | ||
4880 | <section id="misc-devices-IEC958"> | |
4881 | <title>IEC958 (S/PDIF)</title> | |
4882 | <para> | |
4883 | Usually the controls for IEC958 devices are implemented via | |
4884 | control interface. There is a macro to compose a name string for | |
4885 | IEC958 controls, <function>SNDRV_CTL_NAME_IEC958()</function> | |
4886 | defined in <filename><include/asound.h></filename>. | |
4887 | </para> | |
4888 | ||
4889 | <para> | |
4890 | There are some standard controls for IEC958 status bits. These | |
4891 | controls use the type <type>SNDRV_CTL_ELEM_TYPE_IEC958</type>, | |
4892 | and the size of element is fixed as 4 bytes array | |
4893 | (value.iec958.status[x]). For <structfield>info</structfield> | |
4894 | callback, you don't specify | |
4895 | the value field for this type (the count field must be set, | |
4896 | though). | |
4897 | </para> | |
4898 | ||
4899 | <para> | |
4900 | <quote>IEC958 Playback Con Mask</quote> is used to return the | |
4901 | bit-mask for the IEC958 status bits of consumer mode. Similarly, | |
4902 | <quote>IEC958 Playback Pro Mask</quote> returns the bitmask for | |
4903 | professional mode. They are read-only controls, and are defined | |
4904 | as MIXER controls (iface = | |
4905 | <constant>SNDRV_CTL_ELEM_IFACE_MIXER</constant>). | |
4906 | </para> | |
4907 | ||
4908 | <para> | |
4909 | Meanwhile, <quote>IEC958 Playback Default</quote> control is | |
4910 | defined for getting and setting the current default IEC958 | |
4911 | bits. Note that this one is usually defined as a PCM control | |
4912 | (iface = <constant>SNDRV_CTL_ELEM_IFACE_PCM</constant>), | |
4913 | although in some places it's defined as a MIXER control. | |
4914 | </para> | |
4915 | ||
4916 | <para> | |
4917 | In addition, you can define the control switches to | |
4918 | enable/disable or to set the raw bit mode. The implementation | |
4919 | will depend on the chip, but the control should be named as | |
4920 | <quote>IEC958 xxx</quote>, preferably using | |
4921 | <function>SNDRV_CTL_NAME_IEC958()</function> macro. | |
4922 | </para> | |
4923 | ||
4924 | <para> | |
4925 | You can find several cases, for example, | |
4926 | <filename>pci/emu10k1</filename>, | |
4927 | <filename>pci/ice1712</filename>, or | |
4928 | <filename>pci/cmipci.c</filename>. | |
4929 | </para> | |
4930 | </section> | |
4931 | ||
4932 | </chapter> | |
4933 | ||
4934 | ||
4935 | <!-- ****************************************************** --> | |
4936 | <!-- Buffer and Memory Management --> | |
4937 | <!-- ****************************************************** --> | |
4938 | <chapter id="buffer-and-memory"> | |
4939 | <title>Buffer and Memory Management</title> | |
4940 | ||
4941 | <section id="buffer-and-memory-buffer-types"> | |
4942 | <title>Buffer Types</title> | |
4943 | <para> | |
4944 | ALSA provides several different buffer allocation functions | |
4945 | depending on the bus and the architecture. All these have a | |
4946 | consistent API. The allocation of physically-contiguous pages is | |
4947 | done via | |
4948 | <function>snd_malloc_xxx_pages()</function> function, where xxx | |
4949 | is the bus type. | |
4950 | </para> | |
4951 | ||
4952 | <para> | |
4953 | The allocation of pages with fallback is | |
4954 | <function>snd_malloc_xxx_pages_fallback()</function>. This | |
4955 | function tries to allocate the specified pages but if the pages | |
4956 | are not available, it tries to reduce the page sizes until the | |
4957 | enough space is found. | |
4958 | </para> | |
4959 | ||
4960 | <para> | |
4961 | For releasing the space, call | |
4962 | <function>snd_free_xxx_pages()</function> function. | |
4963 | </para> | |
4964 | ||
4965 | <para> | |
4966 | Usually, ALSA drivers try to allocate and reserve | |
4967 | a large contiguous physical space | |
4968 | at the time the module is loaded for the later use. | |
4969 | This is called <quote>pre-allocation</quote>. | |
4970 | As already written, you can call the following function at the | |
4971 | construction of pcm instance (in the case of PCI bus). | |
4972 | ||
4973 | <informalexample> | |
4974 | <programlisting> | |
4975 | <![CDATA[ | |
4976 | snd_pcm_lib_preallocate_pages_for_all(pcm, SNDRV_DMA_TYPE_DEV, | |
4977 | snd_dma_pci_data(pci), size, max); | |
4978 | ]]> | |
4979 | </programlisting> | |
4980 | </informalexample> | |
4981 | ||
4982 | where <parameter>size</parameter> is the byte size to be | |
4983 | pre-allocated and the <parameter>max</parameter> is the maximal | |
4984 | size to be changed via <filename>prealloc</filename> proc file. | |
4985 | The allocator will try to get as large area as possible | |
4986 | within the given size. | |
4987 | </para> | |
4988 | ||
4989 | <para> | |
4990 | The second argument (type) and the third argument (device pointer) | |
4991 | are dependent on the bus. | |
4992 | In the case of ISA bus, pass <function>snd_dma_isa_data()</function> | |
4993 | as the third argument with <constant>SNDRV_DMA_TYPE_DEV</constant> type. | |
4994 | For the continuous buffer unrelated to the bus can be pre-allocated | |
4995 | with <constant>SNDRV_DMA_TYPE_CONTINUOUS</constant> type and the | |
4996 | <function>snd_dma_continuous_data(GFP_KERNEL)</function> device pointer, | |
4997 | whereh <constant>GFP_KERNEL</constant> is the kernel allocation flag to | |
4998 | use. For the SBUS, <constant>SNDRV_DMA_TYPE_SBUS</constant> and | |
4999 | <function>snd_dma_sbus_data(sbus_dev)</function> are used instead. | |
5000 | For the PCI scatter-gather buffers, use | |
5001 | <constant>SNDRV_DMA_TYPE_DEV_SG</constant> with | |
5002 | <function>snd_dma_pci_data(pci)</function> | |
5003 | (see the section | |
5004 | <link linkend="buffer-and-memory-non-contiguous"><citetitle>Non-Contiguous Buffers | |
5005 | </citetitle></link>). | |
5006 | </para> | |
5007 | ||
5008 | <para> | |
5009 | Once when the buffer is pre-allocated, you can use the | |
5010 | allocator in the <structfield>hw_params</structfield> callback | |
5011 | ||
5012 | <informalexample> | |
5013 | <programlisting> | |
5014 | <![CDATA[ | |
5015 | snd_pcm_lib_malloc_pages(substream, size); | |
5016 | ]]> | |
5017 | </programlisting> | |
5018 | </informalexample> | |
5019 | ||
5020 | Note that you have to pre-allocate to use this function. | |
5021 | </para> | |
5022 | </section> | |
5023 | ||
5024 | <section id="buffer-and-memory-external-hardware"> | |
5025 | <title>External Hardware Buffers</title> | |
5026 | <para> | |
5027 | Some chips have their own hardware buffers and the DMA | |
5028 | transfer from the host memory is not available. In such a case, | |
5029 | you need to either 1) copy/set the audio data directly to the | |
5030 | external hardware buffer, or 2) make an intermediate buffer and | |
5031 | copy/set the data from it to the external hardware buffer in | |
5032 | interrupts (or in tasklets, preferably). | |
5033 | </para> | |
5034 | ||
5035 | <para> | |
5036 | The first case works fine if the external hardware buffer is enough | |
5037 | large. This method doesn't need any extra buffers and thus is | |
5038 | more effective. You need to define the | |
5039 | <structfield>copy</structfield> and | |
5040 | <structfield>silence</structfield> callbacks for | |
5041 | the data transfer. However, there is a drawback: it cannot | |
5042 | be mmapped. The examples are GUS's GF1 PCM or emu8000's | |
5043 | wavetable PCM. | |
5044 | </para> | |
5045 | ||
5046 | <para> | |
5047 | The second case allows the mmap of the buffer, although you have | |
5048 | to handle an interrupt or a tasklet for transferring the data | |
5049 | from the intermediate buffer to the hardware buffer. You can find an | |
5050 | example in vxpocket driver. | |
5051 | </para> | |
5052 | ||
5053 | <para> | |
5054 | Another case is that the chip uses a PCI memory-map | |
5055 | region for the buffer instead of the host memory. In this case, | |
5056 | mmap is available only on certain architectures like intel. In | |
5057 | non-mmap mode, the data cannot be transferred as the normal | |
5058 | way. Thus you need to define <structfield>copy</structfield> and | |
5059 | <structfield>silence</structfield> callbacks as well | |
5060 | as in the cases above. The examples are found in | |
5061 | <filename>rme32.c</filename> and <filename>rme96.c</filename>. | |
5062 | </para> | |
5063 | ||
5064 | <para> | |
5065 | The implementation of <structfield>copy</structfield> and | |
5066 | <structfield>silence</structfield> callbacks depends upon | |
5067 | whether the hardware supports interleaved or non-interleaved | |
5068 | samples. The <structfield>copy</structfield> callback is | |
5069 | defined like below, a bit | |
5070 | differently depending whether the direction is playback or | |
5071 | capture: | |
5072 | ||
5073 | <informalexample> | |
5074 | <programlisting> | |
5075 | <![CDATA[ | |
446ab5f5 | 5076 | static int playback_copy(struct snd_pcm_substream *substream, int channel, |
1da177e4 | 5077 | snd_pcm_uframes_t pos, void *src, snd_pcm_uframes_t count); |
446ab5f5 | 5078 | static int capture_copy(struct snd_pcm_substream *substream, int channel, |
1da177e4 LT |
5079 | snd_pcm_uframes_t pos, void *dst, snd_pcm_uframes_t count); |
5080 | ]]> | |
5081 | </programlisting> | |
5082 | </informalexample> | |
5083 | </para> | |
5084 | ||
5085 | <para> | |
5086 | In the case of interleaved samples, the second argument | |
5087 | (<parameter>channel</parameter>) is not used. The third argument | |
5088 | (<parameter>pos</parameter>) points the | |
5089 | current position offset in frames. | |
5090 | </para> | |
5091 | ||
5092 | <para> | |
5093 | The meaning of the fourth argument is different between | |
5094 | playback and capture. For playback, it holds the source data | |
5095 | pointer, and for capture, it's the destination data pointer. | |
5096 | </para> | |
5097 | ||
5098 | <para> | |
5099 | The last argument is the number of frames to be copied. | |
5100 | </para> | |
5101 | ||
5102 | <para> | |
5103 | What you have to do in this callback is again different | |
5104 | between playback and capture directions. In the case of | |
5105 | playback, you do: copy the given amount of data | |
5106 | (<parameter>count</parameter>) at the specified pointer | |
5107 | (<parameter>src</parameter>) to the specified offset | |
5108 | (<parameter>pos</parameter>) on the hardware buffer. When | |
5109 | coded like memcpy-like way, the copy would be like: | |
5110 | ||
5111 | <informalexample> | |
5112 | <programlisting> | |
5113 | <![CDATA[ | |
5114 | my_memcpy(my_buffer + frames_to_bytes(runtime, pos), src, | |
5115 | frames_to_bytes(runtime, count)); | |
5116 | ]]> | |
5117 | </programlisting> | |
5118 | </informalexample> | |
5119 | </para> | |
5120 | ||
5121 | <para> | |
5122 | For the capture direction, you do: copy the given amount of | |
5123 | data (<parameter>count</parameter>) at the specified offset | |
5124 | (<parameter>pos</parameter>) on the hardware buffer to the | |
5125 | specified pointer (<parameter>dst</parameter>). | |
5126 | ||
5127 | <informalexample> | |
5128 | <programlisting> | |
5129 | <![CDATA[ | |
5130 | my_memcpy(dst, my_buffer + frames_to_bytes(runtime, pos), | |
5131 | frames_to_bytes(runtime, count)); | |
5132 | ]]> | |
5133 | </programlisting> | |
5134 | </informalexample> | |
5135 | ||
5136 | Note that both of the position and the data amount are given | |
5137 | in frames. | |
5138 | </para> | |
5139 | ||
5140 | <para> | |
5141 | In the case of non-interleaved samples, the implementation | |
5142 | will be a bit more complicated. | |
5143 | </para> | |
5144 | ||
5145 | <para> | |
5146 | You need to check the channel argument, and if it's -1, copy | |
5147 | the whole channels. Otherwise, you have to copy only the | |
5148 | specified channel. Please check | |
5149 | <filename>isa/gus/gus_pcm.c</filename> as an example. | |
5150 | </para> | |
5151 | ||
5152 | <para> | |
5153 | The <structfield>silence</structfield> callback is also | |
5154 | implemented in a similar way. | |
5155 | ||
5156 | <informalexample> | |
5157 | <programlisting> | |
5158 | <![CDATA[ | |
446ab5f5 | 5159 | static int silence(struct snd_pcm_substream *substream, int channel, |
1da177e4 LT |
5160 | snd_pcm_uframes_t pos, snd_pcm_uframes_t count); |
5161 | ]]> | |
5162 | </programlisting> | |
5163 | </informalexample> | |
5164 | </para> | |
5165 | ||
5166 | <para> | |
5167 | The meanings of arguments are identical with the | |
5168 | <structfield>copy</structfield> | |
5169 | callback, although there is no <parameter>src/dst</parameter> | |
5170 | argument. In the case of interleaved samples, the channel | |
5171 | argument has no meaning, as well as on | |
5172 | <structfield>copy</structfield> callback. | |
5173 | </para> | |
5174 | ||
5175 | <para> | |
5176 | The role of <structfield>silence</structfield> callback is to | |
5177 | set the given amount | |
5178 | (<parameter>count</parameter>) of silence data at the | |
5179 | specified offset (<parameter>pos</parameter>) on the hardware | |
5180 | buffer. Suppose that the data format is signed (that is, the | |
5181 | silent-data is 0), and the implementation using a memset-like | |
5182 | function would be like: | |
5183 | ||
5184 | <informalexample> | |
5185 | <programlisting> | |
5186 | <![CDATA[ | |
5187 | my_memcpy(my_buffer + frames_to_bytes(runtime, pos), 0, | |
5188 | frames_to_bytes(runtime, count)); | |
5189 | ]]> | |
5190 | </programlisting> | |
5191 | </informalexample> | |
5192 | </para> | |
5193 | ||
5194 | <para> | |
5195 | In the case of non-interleaved samples, again, the | |
5196 | implementation becomes a bit more complicated. See, for example, | |
5197 | <filename>isa/gus/gus_pcm.c</filename>. | |
5198 | </para> | |
5199 | </section> | |
5200 | ||
5201 | <section id="buffer-and-memory-non-contiguous"> | |
5202 | <title>Non-Contiguous Buffers</title> | |
5203 | <para> | |
5204 | If your hardware supports the page table like emu10k1 or the | |
5205 | buffer descriptors like via82xx, you can use the scatter-gather | |
5206 | (SG) DMA. ALSA provides an interface for handling SG-buffers. | |
5207 | The API is provided in <filename><sound/pcm.h></filename>. | |
5208 | </para> | |
5209 | ||
5210 | <para> | |
5211 | For creating the SG-buffer handler, call | |
5212 | <function>snd_pcm_lib_preallocate_pages()</function> or | |
5213 | <function>snd_pcm_lib_preallocate_pages_for_all()</function> | |
5214 | with <constant>SNDRV_DMA_TYPE_DEV_SG</constant> | |
5215 | in the PCM constructor like other PCI pre-allocator. | |
5216 | You need to pass the <function>snd_dma_pci_data(pci)</function>, | |
5217 | where pci is the struct <structname>pci_dev</structname> pointer | |
5218 | of the chip as well. | |
44275f18 | 5219 | The <type>struct snd_sg_buf</type> instance is created as |
1da177e4 LT |
5220 | substream->dma_private. You can cast |
5221 | the pointer like: | |
5222 | ||
5223 | <informalexample> | |
5224 | <programlisting> | |
5225 | <![CDATA[ | |
44275f18 | 5226 | struct snd_sg_buf *sgbuf = (struct snd_sg_buf *)substream->dma_private; |
1da177e4 LT |
5227 | ]]> |
5228 | </programlisting> | |
5229 | </informalexample> | |
5230 | </para> | |
5231 | ||
5232 | <para> | |
5233 | Then call <function>snd_pcm_lib_malloc_pages()</function> | |
5234 | in <structfield>hw_params</structfield> callback | |
5235 | as well as in the case of normal PCI buffer. | |
5236 | The SG-buffer handler will allocate the non-contiguous kernel | |
5237 | pages of the given size and map them onto the virtually contiguous | |
5238 | memory. The virtual pointer is addressed in runtime->dma_area. | |
5239 | The physical address (runtime->dma_addr) is set to zero, | |
5240 | because the buffer is physically non-contigous. | |
5241 | The physical address table is set up in sgbuf->table. | |
5242 | You can get the physical address at a certain offset via | |
5243 | <function>snd_pcm_sgbuf_get_addr()</function>. | |
5244 | </para> | |
5245 | ||
5246 | <para> | |
5247 | When a SG-handler is used, you need to set | |
5248 | <function>snd_pcm_sgbuf_ops_page</function> as | |
5249 | the <structfield>page</structfield> callback. | |
5250 | (See <link linkend="pcm-interface-operators-page-callback"> | |
5251 | <citetitle>page callback section</citetitle></link>.) | |
5252 | </para> | |
5253 | ||
5254 | <para> | |
5255 | For releasing the data, call | |
5256 | <function>snd_pcm_lib_free_pages()</function> in the | |
5257 | <structfield>hw_free</structfield> callback as usual. | |
5258 | </para> | |
5259 | </section> | |
5260 | ||
5261 | <section id="buffer-and-memory-vmalloced"> | |
5262 | <title>Vmalloc'ed Buffers</title> | |
5263 | <para> | |
5264 | It's possible to use a buffer allocated via | |
5265 | <function>vmalloc</function>, for example, for an intermediate | |
5266 | buffer. Since the allocated pages are not contiguous, you need | |
5267 | to set the <structfield>page</structfield> callback to obtain | |
5268 | the physical address at every offset. | |
5269 | </para> | |
5270 | ||
5271 | <para> | |
5272 | The implementation of <structfield>page</structfield> callback | |
5273 | would be like this: | |
5274 | ||
5275 | <informalexample> | |
5276 | <programlisting> | |
5277 | <![CDATA[ | |
5278 | #include <linux/vmalloc.h> | |
5279 | ||
5280 | /* get the physical page pointer on the given offset */ | |
446ab5f5 | 5281 | static struct page *mychip_page(struct snd_pcm_substream *substream, |
1da177e4 LT |
5282 | unsigned long offset) |
5283 | { | |
5284 | void *pageptr = substream->runtime->dma_area + offset; | |
5285 | return vmalloc_to_page(pageptr); | |
5286 | } | |
5287 | ]]> | |
5288 | </programlisting> | |
5289 | </informalexample> | |
5290 | </para> | |
5291 | </section> | |
5292 | ||
5293 | </chapter> | |
5294 | ||
5295 | ||
5296 | <!-- ****************************************************** --> | |
5297 | <!-- Proc Interface --> | |
5298 | <!-- ****************************************************** --> | |
5299 | <chapter id="proc-interface"> | |
5300 | <title>Proc Interface</title> | |
5301 | <para> | |
5302 | ALSA provides an easy interface for procfs. The proc files are | |
5303 | very useful for debugging. I recommend you set up proc files if | |
5304 | you write a driver and want to get a running status or register | |
5305 | dumps. The API is found in | |
5306 | <filename><sound/info.h></filename>. | |
5307 | </para> | |
5308 | ||
5309 | <para> | |
5310 | For creating a proc file, call | |
5311 | <function>snd_card_proc_new()</function>. | |
5312 | ||
5313 | <informalexample> | |
5314 | <programlisting> | |
5315 | <![CDATA[ | |
446ab5f5 | 5316 | struct snd_info_entry *entry; |
1da177e4 LT |
5317 | int err = snd_card_proc_new(card, "my-file", &entry); |
5318 | ]]> | |
5319 | </programlisting> | |
5320 | </informalexample> | |
5321 | ||
5322 | where the second argument specifies the proc-file name to be | |
5323 | created. The above example will create a file | |
5324 | <filename>my-file</filename> under the card directory, | |
5325 | e.g. <filename>/proc/asound/card0/my-file</filename>. | |
5326 | </para> | |
5327 | ||
5328 | <para> | |
5329 | Like other components, the proc entry created via | |
5330 | <function>snd_card_proc_new()</function> will be registered and | |
5331 | released automatically in the card registration and release | |
5332 | functions. | |
5333 | </para> | |
5334 | ||
5335 | <para> | |
5336 | When the creation is successful, the function stores a new | |
5337 | instance at the pointer given in the third argument. | |
5338 | It is initialized as a text proc file for read only. For using | |
5339 | this proc file as a read-only text file as it is, set the read | |
5340 | callback with a private data via | |
5341 | <function>snd_info_set_text_ops()</function>. | |
5342 | ||
5343 | <informalexample> | |
5344 | <programlisting> | |
5345 | <![CDATA[ | |
bf850204 | 5346 | snd_info_set_text_ops(entry, chip, my_proc_read); |
1da177e4 LT |
5347 | ]]> |
5348 | </programlisting> | |
5349 | </informalexample> | |
5350 | ||
5351 | where the second argument (<parameter>chip</parameter>) is the | |
5352 | private data to be used in the callbacks. The third parameter | |
5353 | specifies the read buffer size and the fourth | |
5354 | (<parameter>my_proc_read</parameter>) is the callback function, which | |
5355 | is defined like | |
5356 | ||
5357 | <informalexample> | |
5358 | <programlisting> | |
5359 | <![CDATA[ | |
446ab5f5 TI |
5360 | static void my_proc_read(struct snd_info_entry *entry, |
5361 | struct snd_info_buffer *buffer); | |
1da177e4 LT |
5362 | ]]> |
5363 | </programlisting> | |
5364 | </informalexample> | |
5365 | ||
5366 | </para> | |
5367 | ||
5368 | <para> | |
5369 | In the read callback, use <function>snd_iprintf()</function> for | |
5370 | output strings, which works just like normal | |
5371 | <function>printf()</function>. For example, | |
5372 | ||
5373 | <informalexample> | |
5374 | <programlisting> | |
5375 | <![CDATA[ | |
446ab5f5 TI |
5376 | static void my_proc_read(struct snd_info_entry *entry, |
5377 | struct snd_info_buffer *buffer) | |
1da177e4 | 5378 | { |
446ab5f5 | 5379 | struct my_chip *chip = entry->private_data; |
1da177e4 LT |
5380 | |
5381 | snd_iprintf(buffer, "This is my chip!\n"); | |
5382 | snd_iprintf(buffer, "Port = %ld\n", chip->port); | |
5383 | } | |
5384 | ]]> | |
5385 | </programlisting> | |
5386 | </informalexample> | |
5387 | </para> | |
5388 | ||
5389 | <para> | |
5390 | The file permission can be changed afterwards. As default, it's | |
5391 | set as read only for all users. If you want to add the write | |
5392 | permission to the user (root as default), set like below: | |
5393 | ||
5394 | <informalexample> | |
5395 | <programlisting> | |
5396 | <![CDATA[ | |
5397 | entry->mode = S_IFREG | S_IRUGO | S_IWUSR; | |
5398 | ]]> | |
5399 | </programlisting> | |
5400 | </informalexample> | |
5401 | ||
5402 | and set the write buffer size and the callback | |
5403 | ||
5404 | <informalexample> | |
5405 | <programlisting> | |
5406 | <![CDATA[ | |
1da177e4 LT |
5407 | entry->c.text.write = my_proc_write; |
5408 | ]]> | |
5409 | </programlisting> | |
5410 | </informalexample> | |
5411 | </para> | |
5412 | ||
1da177e4 LT |
5413 | <para> |
5414 | For the write callback, you can use | |
5415 | <function>snd_info_get_line()</function> to get a text line, and | |
5416 | <function>snd_info_get_str()</function> to retrieve a string from | |
5417 | the line. Some examples are found in | |
5418 | <filename>core/oss/mixer_oss.c</filename>, core/oss/and | |
5419 | <filename>pcm_oss.c</filename>. | |
5420 | </para> | |
5421 | ||
5422 | <para> | |
5423 | For a raw-data proc-file, set the attributes like the following: | |
5424 | ||
5425 | <informalexample> | |
5426 | <programlisting> | |
5427 | <![CDATA[ | |
5428 | static struct snd_info_entry_ops my_file_io_ops = { | |
5429 | .read = my_file_io_read, | |
5430 | }; | |
5431 | ||
5432 | entry->content = SNDRV_INFO_CONTENT_DATA; | |
5433 | entry->private_data = chip; | |
5434 | entry->c.ops = &my_file_io_ops; | |
5435 | entry->size = 4096; | |
5436 | entry->mode = S_IFREG | S_IRUGO; | |
5437 | ]]> | |
5438 | </programlisting> | |
5439 | </informalexample> | |
5440 | </para> | |
5441 | ||
5442 | <para> | |
5443 | The callback is much more complicated than the text-file | |
5444 | version. You need to use a low-level i/o functions such as | |
5445 | <function>copy_from/to_user()</function> to transfer the | |
5446 | data. | |
5447 | ||
5448 | <informalexample> | |
5449 | <programlisting> | |
5450 | <![CDATA[ | |
446ab5f5 | 5451 | static long my_file_io_read(struct snd_info_entry *entry, |
1da177e4 LT |
5452 | void *file_private_data, |
5453 | struct file *file, | |
5454 | char *buf, | |
5455 | unsigned long count, | |
5456 | unsigned long pos) | |
5457 | { | |
5458 | long size = count; | |
5459 | if (pos + size > local_max_size) | |
5460 | size = local_max_size - pos; | |
5461 | if (copy_to_user(buf, local_data + pos, size)) | |
5462 | return -EFAULT; | |
5463 | return size; | |
5464 | } | |
5465 | ]]> | |
5466 | </programlisting> | |
5467 | </informalexample> | |
5468 | </para> | |
5469 | ||
5470 | </chapter> | |
5471 | ||
5472 | ||
5473 | <!-- ****************************************************** --> | |
5474 | <!-- Power Management --> | |
5475 | <!-- ****************************************************** --> | |
5476 | <chapter id="power-management"> | |
5477 | <title>Power Management</title> | |
5478 | <para> | |
670e9f34 | 5479 | If the chip is supposed to work with suspend/resume |
1da177e4 LT |
5480 | functions, you need to add the power-management codes to the |
5481 | driver. The additional codes for the power-management should be | |
5482 | <function>ifdef</function>'ed with | |
5483 | <constant>CONFIG_PM</constant>. | |
5484 | </para> | |
5485 | ||
5fe76e4d TI |
5486 | <para> |
5487 | If the driver supports the suspend/resume | |
5488 | <emphasis>fully</emphasis>, that is, the device can be | |
5489 | properly resumed to the status at the suspend is called, | |
5490 | you can set <constant>SNDRV_PCM_INFO_RESUME</constant> flag | |
5491 | to pcm info field. Usually, this is possible when the | |
5492 | registers of ths chip can be safely saved and restored to the | |
5493 | RAM. If this is set, the trigger callback is called with | |
5494 | <constant>SNDRV_PCM_TRIGGER_RESUME</constant> after resume | |
5495 | callback is finished. | |
5496 | </para> | |
5497 | ||
5498 | <para> | |
5499 | Even if the driver doesn't support PM fully but only the | |
5500 | partial suspend/resume is possible, it's still worthy to | |
5501 | implement suspend/resume callbacks. In such a case, applications | |
5502 | would reset the status by calling | |
5503 | <function>snd_pcm_prepare()</function> and restart the stream | |
5504 | appropriately. Hence, you can define suspend/resume callbacks | |
5505 | below but don't set <constant>SNDRV_PCM_INFO_RESUME</constant> | |
5506 | info flag to the PCM. | |
5507 | </para> | |
5508 | ||
5509 | <para> | |
5510 | Note that the trigger with SUSPEND can be always called when | |
5511 | <function>snd_pcm_suspend_all</function> is called, | |
5512 | regardless of <constant>SNDRV_PCM_INFO_RESUME</constant> flag. | |
5513 | The <constant>RESUME</constant> flag affects only the behavior | |
5514 | of <function>snd_pcm_resume()</function>. | |
5515 | (Thus, in theory, | |
5516 | <constant>SNDRV_PCM_TRIGGER_RESUME</constant> isn't needed | |
5517 | to be handled in the trigger callback when no | |
5518 | <constant>SNDRV_PCM_INFO_RESUME</constant> flag is set. But, | |
5519 | it's better to keep it for compatibility reason.) | |
5520 | </para> | |
1da177e4 | 5521 | <para> |
5fe76e4d TI |
5522 | In the earlier version of ALSA drivers, a common |
5523 | power-management layer was provided, but it has been removed. | |
5524 | The driver needs to define the suspend/resume hooks according to | |
5525 | the bus the device is assigned. In the case of PCI driver, the | |
5526 | callbacks look like below: | |
1da177e4 LT |
5527 | |
5528 | <informalexample> | |
5529 | <programlisting> | |
5530 | <![CDATA[ | |
5531 | #ifdef CONFIG_PM | |
5fe76e4d | 5532 | static int snd_my_suspend(struct pci_dev *pci, pm_message_t state) |
1da177e4 | 5533 | { |
5fe76e4d | 5534 | .... /* do things for suspsend */ |
1da177e4 LT |
5535 | return 0; |
5536 | } | |
5fe76e4d | 5537 | static int snd_my_resume(struct pci_dev *pci) |
1da177e4 | 5538 | { |
5fe76e4d | 5539 | .... /* do things for suspsend */ |
1da177e4 LT |
5540 | return 0; |
5541 | } | |
5542 | #endif | |
5543 | ]]> | |
5544 | </programlisting> | |
5545 | </informalexample> | |
5546 | </para> | |
5547 | ||
5548 | <para> | |
5549 | The scheme of the real suspend job is as following. | |
5550 | ||
5551 | <orderedlist> | |
5fe76e4d TI |
5552 | <listitem><para>Retrieve the card and the chip data.</para></listitem> |
5553 | <listitem><para>Call <function>snd_power_change_state()</function> with | |
5554 | <constant>SNDRV_CTL_POWER_D3hot</constant> to change the | |
5555 | power status.</para></listitem> | |
1da177e4 | 5556 | <listitem><para>Call <function>snd_pcm_suspend_all()</function> to suspend the running PCM streams.</para></listitem> |
5fe76e4d | 5557 | <listitem><para>If AC97 codecs are used, call |
a7306336 | 5558 | <function>snd_ac97_suspend()</function> for each codec.</para></listitem> |
1da177e4 LT |
5559 | <listitem><para>Save the register values if necessary.</para></listitem> |
5560 | <listitem><para>Stop the hardware if necessary.</para></listitem> | |
5fe76e4d TI |
5561 | <listitem><para>Disable the PCI device by calling |
5562 | <function>pci_disable_device()</function>. Then, call | |
5563 | <function>pci_save_state()</function> at last.</para></listitem> | |
1da177e4 LT |
5564 | </orderedlist> |
5565 | </para> | |
5566 | ||
5567 | <para> | |
5568 | A typical code would be like: | |
5569 | ||
5570 | <informalexample> | |
5571 | <programlisting> | |
5572 | <![CDATA[ | |
32357988 | 5573 | static int mychip_suspend(struct pci_dev *pci, pm_message_t state) |
1da177e4 LT |
5574 | { |
5575 | /* (1) */ | |
5fe76e4d TI |
5576 | struct snd_card *card = pci_get_drvdata(pci); |
5577 | struct mychip *chip = card->private_data; | |
1da177e4 | 5578 | /* (2) */ |
5fe76e4d | 5579 | snd_power_change_state(card, SNDRV_CTL_POWER_D3hot); |
1da177e4 | 5580 | /* (3) */ |
5fe76e4d | 5581 | snd_pcm_suspend_all(chip->pcm); |
1da177e4 | 5582 | /* (4) */ |
5fe76e4d | 5583 | snd_ac97_suspend(chip->ac97); |
1da177e4 | 5584 | /* (5) */ |
5fe76e4d TI |
5585 | snd_mychip_save_registers(chip); |
5586 | /* (6) */ | |
5587 | snd_mychip_stop_hardware(chip); | |
5588 | /* (7) */ | |
5589 | pci_disable_device(pci); | |
5590 | pci_save_state(pci); | |
1da177e4 LT |
5591 | return 0; |
5592 | } | |
5593 | ]]> | |
5594 | </programlisting> | |
5595 | </informalexample> | |
5596 | </para> | |
5597 | ||
5598 | <para> | |
5599 | The scheme of the real resume job is as following. | |
5600 | ||
5601 | <orderedlist> | |
5fe76e4d TI |
5602 | <listitem><para>Retrieve the card and the chip data.</para></listitem> |
5603 | <listitem><para>Set up PCI. First, call <function>pci_restore_state()</function>. | |
5604 | Then enable the pci device again by calling <function>pci_enable_device()</function>. | |
5605 | Call <function>pci_set_master()</function> if necessary, too.</para></listitem> | |
1da177e4 LT |
5606 | <listitem><para>Re-initialize the chip.</para></listitem> |
5607 | <listitem><para>Restore the saved registers if necessary.</para></listitem> | |
5608 | <listitem><para>Resume the mixer, e.g. calling | |
5609 | <function>snd_ac97_resume()</function>.</para></listitem> | |
5610 | <listitem><para>Restart the hardware (if any).</para></listitem> | |
5fe76e4d TI |
5611 | <listitem><para>Call <function>snd_power_change_state()</function> with |
5612 | <constant>SNDRV_CTL_POWER_D0</constant> to notify the processes.</para></listitem> | |
1da177e4 LT |
5613 | </orderedlist> |
5614 | </para> | |
5615 | ||
5616 | <para> | |
5617 | A typical code would be like: | |
5618 | ||
5619 | <informalexample> | |
5620 | <programlisting> | |
5621 | <![CDATA[ | |
5fe76e4d | 5622 | static int mychip_resume(struct pci_dev *pci) |
1da177e4 LT |
5623 | { |
5624 | /* (1) */ | |
5fe76e4d TI |
5625 | struct snd_card *card = pci_get_drvdata(pci); |
5626 | struct mychip *chip = card->private_data; | |
1da177e4 | 5627 | /* (2) */ |
5fe76e4d TI |
5628 | pci_restore_state(pci); |
5629 | pci_enable_device(pci); | |
5630 | pci_set_master(pci); | |
1da177e4 LT |
5631 | /* (3) */ |
5632 | snd_mychip_reinit_chip(chip); | |
5633 | /* (4) */ | |
5634 | snd_mychip_restore_registers(chip); | |
5635 | /* (5) */ | |
5636 | snd_ac97_resume(chip->ac97); | |
5637 | /* (6) */ | |
5638 | snd_mychip_restart_chip(chip); | |
5fe76e4d TI |
5639 | /* (7) */ |
5640 | snd_power_change_state(card, SNDRV_CTL_POWER_D0); | |
1da177e4 LT |
5641 | return 0; |
5642 | } | |
5643 | ]]> | |
5644 | </programlisting> | |
5645 | </informalexample> | |
5646 | </para> | |
5647 | ||
5648 | <para> | |
5fe76e4d TI |
5649 | As shown in the above, it's better to save registers after |
5650 | suspending the PCM operations via | |
5651 | <function>snd_pcm_suspend_all()</function> or | |
5652 | <function>snd_pcm_suspend()</function>. It means that the PCM | |
5653 | streams are already stoppped when the register snapshot is | |
5654 | taken. But, remind that you don't have to restart the PCM | |
5655 | stream in the resume callback. It'll be restarted via | |
5656 | trigger call with <constant>SNDRV_PCM_TRIGGER_RESUME</constant> | |
5657 | when necessary. | |
5658 | </para> | |
5659 | ||
5660 | <para> | |
5661 | OK, we have all callbacks now. Let's set them up. In the | |
5662 | initialization of the card, make sure that you can get the chip | |
5663 | data from the card instance, typically via | |
5664 | <structfield>private_data</structfield> field, in case you | |
5665 | created the chip data individually. | |
5666 | ||
5667 | <informalexample> | |
5668 | <programlisting> | |
5669 | <![CDATA[ | |
5670 | static int __devinit snd_mychip_probe(struct pci_dev *pci, | |
5671 | const struct pci_device_id *pci_id) | |
5672 | { | |
5673 | .... | |
5674 | struct snd_card *card; | |
5675 | struct mychip *chip; | |
5676 | .... | |
5677 | card = snd_card_new(index[dev], id[dev], THIS_MODULE, NULL); | |
5678 | .... | |
5679 | chip = kzalloc(sizeof(*chip), GFP_KERNEL); | |
5680 | .... | |
5681 | card->private_data = chip; | |
5682 | .... | |
5683 | } | |
5684 | ]]> | |
5685 | </programlisting> | |
5686 | </informalexample> | |
5687 | ||
5688 | When you created the chip data with | |
5689 | <function>snd_card_new()</function>, it's anyway accessible | |
5690 | via <structfield>private_data</structfield> field. | |
1da177e4 LT |
5691 | |
5692 | <informalexample> | |
5693 | <programlisting> | |
5694 | <![CDATA[ | |
5695 | static int __devinit snd_mychip_probe(struct pci_dev *pci, | |
5696 | const struct pci_device_id *pci_id) | |
5697 | { | |
5698 | .... | |
446ab5f5 TI |
5699 | struct snd_card *card; |
5700 | struct mychip *chip; | |
1da177e4 | 5701 | .... |
5fe76e4d TI |
5702 | card = snd_card_new(index[dev], id[dev], THIS_MODULE, |
5703 | sizeof(struct mychip)); | |
5704 | .... | |
5705 | chip = card->private_data; | |
1da177e4 LT |
5706 | .... |
5707 | } | |
5708 | ]]> | |
5709 | </programlisting> | |
5710 | </informalexample> | |
5711 | ||
1da177e4 LT |
5712 | </para> |
5713 | ||
5714 | <para> | |
5fe76e4d TI |
5715 | If you need a space for saving the registers, allocate the |
5716 | buffer for it here, too, since it would be fatal | |
1da177e4 LT |
5717 | if you cannot allocate a memory in the suspend phase. |
5718 | The allocated buffer should be released in the corresponding | |
5719 | destructor. | |
5720 | </para> | |
5721 | ||
5722 | <para> | |
5fe76e4d | 5723 | And next, set suspend/resume callbacks to the pci_driver. |
1da177e4 LT |
5724 | |
5725 | <informalexample> | |
5726 | <programlisting> | |
5727 | <![CDATA[ | |
5728 | static struct pci_driver driver = { | |
5729 | .name = "My Chip", | |
5730 | .id_table = snd_my_ids, | |
5731 | .probe = snd_my_probe, | |
5732 | .remove = __devexit_p(snd_my_remove), | |
5fe76e4d TI |
5733 | #ifdef CONFIG_PM |
5734 | .suspend = snd_my_suspend, | |
5735 | .resume = snd_my_resume, | |
5736 | #endif | |
1da177e4 LT |
5737 | }; |
5738 | ]]> | |
5739 | </programlisting> | |
5740 | </informalexample> | |
5741 | </para> | |
5742 | ||
5743 | </chapter> | |
5744 | ||
5745 | ||
5746 | <!-- ****************************************************** --> | |
5747 | <!-- Module Parameters --> | |
5748 | <!-- ****************************************************** --> | |
5749 | <chapter id="module-parameters"> | |
5750 | <title>Module Parameters</title> | |
5751 | <para> | |
5752 | There are standard module options for ALSA. At least, each | |
5753 | module should have <parameter>index</parameter>, | |
5754 | <parameter>id</parameter> and <parameter>enable</parameter> | |
5755 | options. | |
5756 | </para> | |
5757 | ||
5758 | <para> | |
5759 | If the module supports multiple cards (usually up to | |
5760 | 8 = <constant>SNDRV_CARDS</constant> cards), they should be | |
5761 | arrays. The default initial values are defined already as | |
5762 | constants for ease of programming: | |
5763 | ||
5764 | <informalexample> | |
5765 | <programlisting> | |
5766 | <![CDATA[ | |
5767 | static int index[SNDRV_CARDS] = SNDRV_DEFAULT_IDX; | |
5768 | static char *id[SNDRV_CARDS] = SNDRV_DEFAULT_STR; | |
5769 | static int enable[SNDRV_CARDS] = SNDRV_DEFAULT_ENABLE_PNP; | |
5770 | ]]> | |
5771 | </programlisting> | |
5772 | </informalexample> | |
5773 | </para> | |
5774 | ||
5775 | <para> | |
5776 | If the module supports only a single card, they could be single | |
5777 | variables, instead. <parameter>enable</parameter> option is not | |
5778 | always necessary in this case, but it wouldn't be so bad to have a | |
5779 | dummy option for compatibility. | |
5780 | </para> | |
5781 | ||
5782 | <para> | |
5783 | The module parameters must be declared with the standard | |
5784 | <function>module_param()()</function>, | |
5785 | <function>module_param_array()()</function> and | |
5786 | <function>MODULE_PARM_DESC()</function> macros. | |
5787 | </para> | |
5788 | ||
5789 | <para> | |
5790 | The typical coding would be like below: | |
5791 | ||
5792 | <informalexample> | |
5793 | <programlisting> | |
5794 | <![CDATA[ | |
5795 | #define CARD_NAME "My Chip" | |
5796 | ||
5797 | module_param_array(index, int, NULL, 0444); | |
5798 | MODULE_PARM_DESC(index, "Index value for " CARD_NAME " soundcard."); | |
5799 | module_param_array(id, charp, NULL, 0444); | |
5800 | MODULE_PARM_DESC(id, "ID string for " CARD_NAME " soundcard."); | |
5801 | module_param_array(enable, bool, NULL, 0444); | |
5802 | MODULE_PARM_DESC(enable, "Enable " CARD_NAME " soundcard."); | |
5803 | ]]> | |
5804 | </programlisting> | |
5805 | </informalexample> | |
5806 | </para> | |
5807 | ||
5808 | <para> | |
5809 | Also, don't forget to define the module description, classes, | |
5810 | license and devices. Especially, the recent modprobe requires to | |
5811 | define the module license as GPL, etc., otherwise the system is | |
5812 | shown as <quote>tainted</quote>. | |
5813 | ||
5814 | <informalexample> | |
5815 | <programlisting> | |
5816 | <![CDATA[ | |
5817 | MODULE_DESCRIPTION("My Chip"); | |
5818 | MODULE_LICENSE("GPL"); | |
5819 | MODULE_SUPPORTED_DEVICE("{{Vendor,My Chip Name}}"); | |
5820 | ]]> | |
5821 | </programlisting> | |
5822 | </informalexample> | |
5823 | </para> | |
5824 | ||
5825 | </chapter> | |
5826 | ||
5827 | ||
5828 | <!-- ****************************************************** --> | |
5829 | <!-- How To Put Your Driver --> | |
5830 | <!-- ****************************************************** --> | |
5831 | <chapter id="how-to-put-your-driver"> | |
5832 | <title>How To Put Your Driver Into ALSA Tree</title> | |
5833 | <section> | |
5834 | <title>General</title> | |
5835 | <para> | |
5836 | So far, you've learned how to write the driver codes. | |
5837 | And you might have a question now: how to put my own | |
5838 | driver into the ALSA driver tree? | |
5839 | Here (finally :) the standard procedure is described briefly. | |
5840 | </para> | |
5841 | ||
5842 | <para> | |
5843 | Suppose that you'll create a new PCI driver for the card | |
5844 | <quote>xyz</quote>. The card module name would be | |
5845 | snd-xyz. The new driver is usually put into alsa-driver | |
5846 | tree, <filename>alsa-driver/pci</filename> directory in | |
5847 | the case of PCI cards. | |
5848 | Then the driver is evaluated, audited and tested | |
5849 | by developers and users. After a certain time, the driver | |
5850 | will go to alsa-kernel tree (to the corresponding directory, | |
5851 | such as <filename>alsa-kernel/pci</filename>) and eventually | |
5852 | integrated into Linux 2.6 tree (the directory would be | |
5853 | <filename>linux/sound/pci</filename>). | |
5854 | </para> | |
5855 | ||
5856 | <para> | |
5857 | In the following sections, the driver code is supposed | |
5858 | to be put into alsa-driver tree. The two cases are assumed: | |
5859 | a driver consisting of a single source file and one consisting | |
5860 | of several source files. | |
5861 | </para> | |
5862 | </section> | |
5863 | ||
5864 | <section> | |
5865 | <title>Driver with A Single Source File</title> | |
5866 | <para> | |
5867 | <orderedlist> | |
5868 | <listitem> | |
5869 | <para> | |
5870 | Modify alsa-driver/pci/Makefile | |
5871 | </para> | |
5872 | ||
5873 | <para> | |
5874 | Suppose you have a file xyz.c. Add the following | |
5875 | two lines | |
5876 | <informalexample> | |
5877 | <programlisting> | |
5878 | <![CDATA[ | |
5879 | snd-xyz-objs := xyz.o | |
5880 | obj-$(CONFIG_SND_XYZ) += snd-xyz.o | |
5881 | ]]> | |
5882 | </programlisting> | |
5883 | </informalexample> | |
5884 | </para> | |
5885 | </listitem> | |
5886 | ||
5887 | <listitem> | |
5888 | <para> | |
5889 | Create the Kconfig entry | |
5890 | </para> | |
5891 | ||
5892 | <para> | |
5893 | Add the new entry of Kconfig for your xyz driver. | |
5894 | <informalexample> | |
5895 | <programlisting> | |
5896 | <![CDATA[ | |
5897 | config SND_XYZ | |
5898 | tristate "Foobar XYZ" | |
5899 | depends on SND | |
5900 | select SND_PCM | |
5901 | help | |
5902 | Say Y here to include support for Foobar XYZ soundcard. | |
5903 | ||
5904 | To compile this driver as a module, choose M here: the module | |
5905 | will be called snd-xyz. | |
5906 | ]]> | |
5907 | </programlisting> | |
5908 | </informalexample> | |
5909 | ||
5910 | the line, select SND_PCM, specifies that the driver xyz supports | |
5911 | PCM. In addition to SND_PCM, the following components are | |
5912 | supported for select command: | |
5913 | SND_RAWMIDI, SND_TIMER, SND_HWDEP, SND_MPU401_UART, | |
5914 | SND_OPL3_LIB, SND_OPL4_LIB, SND_VX_LIB, SND_AC97_CODEC. | |
5915 | Add the select command for each supported component. | |
5916 | </para> | |
5917 | ||
5918 | <para> | |
5919 | Note that some selections imply the lowlevel selections. | |
5920 | For example, PCM includes TIMER, MPU401_UART includes RAWMIDI, | |
5921 | AC97_CODEC includes PCM, and OPL3_LIB includes HWDEP. | |
5922 | You don't need to give the lowlevel selections again. | |
5923 | </para> | |
5924 | ||
5925 | <para> | |
5926 | For the details of Kconfig script, refer to the kbuild | |
5927 | documentation. | |
5928 | </para> | |
5929 | ||
5930 | </listitem> | |
5931 | ||
5932 | <listitem> | |
5933 | <para> | |
5934 | Run cvscompile script to re-generate the configure script and | |
5935 | build the whole stuff again. | |
5936 | </para> | |
5937 | </listitem> | |
5938 | </orderedlist> | |
5939 | </para> | |
5940 | </section> | |
5941 | ||
5942 | <section> | |
5943 | <title>Drivers with Several Source Files</title> | |
5944 | <para> | |
5945 | Suppose that the driver snd-xyz have several source files. | |
5946 | They are located in the new subdirectory, | |
5947 | pci/xyz. | |
5948 | ||
5949 | <orderedlist> | |
5950 | <listitem> | |
5951 | <para> | |
5952 | Add a new directory (<filename>xyz</filename>) in | |
5953 | <filename>alsa-driver/pci/Makefile</filename> like below | |
5954 | ||
5955 | <informalexample> | |
5956 | <programlisting> | |
5957 | <![CDATA[ | |
5958 | obj-$(CONFIG_SND) += xyz/ | |
5959 | ]]> | |
5960 | </programlisting> | |
5961 | </informalexample> | |
5962 | </para> | |
5963 | </listitem> | |
5964 | ||
5965 | <listitem> | |
5966 | <para> | |
5967 | Under the directory <filename>xyz</filename>, create a Makefile | |
5968 | ||
5969 | <example> | |
5970 | <title>Sample Makefile for a driver xyz</title> | |
5971 | <programlisting> | |
5972 | <![CDATA[ | |
5973 | ifndef SND_TOPDIR | |
5974 | SND_TOPDIR=../.. | |
5975 | endif | |
5976 | ||
5977 | include $(SND_TOPDIR)/toplevel.config | |
5978 | include $(SND_TOPDIR)/Makefile.conf | |
5979 | ||
5980 | snd-xyz-objs := xyz.o abc.o def.o | |
5981 | ||
5982 | obj-$(CONFIG_SND_XYZ) += snd-xyz.o | |
5983 | ||
5984 | include $(SND_TOPDIR)/Rules.make | |
5985 | ]]> | |
5986 | </programlisting> | |
5987 | </example> | |
5988 | </para> | |
5989 | </listitem> | |
5990 | ||
5991 | <listitem> | |
5992 | <para> | |
5993 | Create the Kconfig entry | |
5994 | </para> | |
5995 | ||
5996 | <para> | |
5997 | This procedure is as same as in the last section. | |
5998 | </para> | |
5999 | </listitem> | |
6000 | ||
6001 | <listitem> | |
6002 | <para> | |
6003 | Run cvscompile script to re-generate the configure script and | |
6004 | build the whole stuff again. | |
6005 | </para> | |
6006 | </listitem> | |
6007 | </orderedlist> | |
6008 | </para> | |
6009 | </section> | |
6010 | ||
6011 | </chapter> | |
6012 | ||
6013 | <!-- ****************************************************** --> | |
6014 | <!-- Useful Functions --> | |
6015 | <!-- ****************************************************** --> | |
6016 | <chapter id="useful-functions"> | |
6017 | <title>Useful Functions</title> | |
6018 | ||
6019 | <section id="useful-functions-snd-printk"> | |
6020 | <title><function>snd_printk()</function> and friends</title> | |
6021 | <para> | |
6022 | ALSA provides a verbose version of | |
6023 | <function>printk()</function> function. If a kernel config | |
6024 | <constant>CONFIG_SND_VERBOSE_PRINTK</constant> is set, this | |
6025 | function prints the given message together with the file name | |
6026 | and the line of the caller. The <constant>KERN_XXX</constant> | |
6027 | prefix is processed as | |
6028 | well as the original <function>printk()</function> does, so it's | |
6029 | recommended to add this prefix, e.g. | |
6030 | ||
6031 | <informalexample> | |
6032 | <programlisting> | |
6033 | <![CDATA[ | |
6034 | snd_printk(KERN_ERR "Oh my, sorry, it's extremely bad!\n"); | |
6035 | ]]> | |
6036 | </programlisting> | |
6037 | </informalexample> | |
6038 | </para> | |
6039 | ||
6040 | <para> | |
6041 | There are also <function>printk()</function>'s for | |
6042 | debugging. <function>snd_printd()</function> can be used for | |
6043 | general debugging purposes. If | |
6044 | <constant>CONFIG_SND_DEBUG</constant> is set, this function is | |
6045 | compiled, and works just like | |
6046 | <function>snd_printk()</function>. If the ALSA is compiled | |
6047 | without the debugging flag, it's ignored. | |
6048 | </para> | |
6049 | ||
6050 | <para> | |
6051 | <function>snd_printdd()</function> is compiled in only when | |
6052 | <constant>CONFIG_SND_DEBUG_DETECT</constant> is set. Please note | |
6053 | that <constant>DEBUG_DETECT</constant> is not set as default | |
6054 | even if you configure the alsa-driver with | |
6055 | <option>--with-debug=full</option> option. You need to give | |
6056 | explicitly <option>--with-debug=detect</option> option instead. | |
6057 | </para> | |
6058 | </section> | |
6059 | ||
6060 | <section id="useful-functions-snd-assert"> | |
6061 | <title><function>snd_assert()</function></title> | |
6062 | <para> | |
6063 | <function>snd_assert()</function> macro is similar with the | |
6064 | normal <function>assert()</function> macro. For example, | |
6065 | ||
6066 | <informalexample> | |
6067 | <programlisting> | |
6068 | <![CDATA[ | |
6069 | snd_assert(pointer != NULL, return -EINVAL); | |
6070 | ]]> | |
6071 | </programlisting> | |
6072 | </informalexample> | |
6073 | </para> | |
6074 | ||
6075 | <para> | |
6076 | The first argument is the expression to evaluate, and the | |
6077 | second argument is the action if it fails. When | |
6078 | <constant>CONFIG_SND_DEBUG</constant>, is set, it will show an | |
7c22f1aa TI |
6079 | error message such as <computeroutput>BUG? (xxx)</computeroutput> |
6080 | together with stack trace. | |
1da177e4 | 6081 | </para> |
1da177e4 | 6082 | <para> |
7c22f1aa | 6083 | When no debug flag is set, this macro is ignored. |
1da177e4 LT |
6084 | </para> |
6085 | </section> | |
6086 | ||
6087 | <section id="useful-functions-snd-bug"> | |
6088 | <title><function>snd_BUG()</function></title> | |
6089 | <para> | |
7c22f1aa TI |
6090 | It shows <computeroutput>BUG?</computeroutput> message and |
6091 | stack trace as well as <function>snd_assert</function> at the point. | |
6092 | It's useful to show that a fatal error happens there. | |
6093 | </para> | |
6094 | <para> | |
6095 | When no debug flag is set, this macro is ignored. | |
1da177e4 LT |
6096 | </para> |
6097 | </section> | |
6098 | </chapter> | |
6099 | ||
6100 | ||
6101 | <!-- ****************************************************** --> | |
6102 | <!-- Acknowledgments --> | |
6103 | <!-- ****************************************************** --> | |
6104 | <chapter id="acknowledments"> | |
6105 | <title>Acknowledgments</title> | |
6106 | <para> | |
6107 | I would like to thank Phil Kerr for his help for improvement and | |
6108 | corrections of this document. | |
6109 | </para> | |
6110 | <para> | |
6111 | Kevin Conder reformatted the original plain-text to the | |
6112 | DocBook format. | |
6113 | </para> | |
6114 | <para> | |
6115 | Giuliano Pochini corrected typos and contributed the example codes | |
6116 | in the hardware constraints section. | |
6117 | </para> | |
6118 | </chapter> | |
6119 | ||
6120 | ||
6121 | </book> |