Documentation/DocBook/device-drivers.tmpl

   1 <?xml version="1.0" encoding="UTF-8"?>
   2 <!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
   3         "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" []>
   4
   5 <book id="LinuxDriversAPI">
   6  <bookinfo>
   7   <title>Linux Device Drivers</title>
   8
   9   <legalnotice>
  10    <para>
  11      This documentation is free software; you can redistribute
  12      it and/or modify it under the terms of the GNU General Public
  13      License as published by the Free Software Foundation; either
  14      version 2 of the License, or (at your option) any later
  15      version.
  16    </para>
  17
  18    <para>
  19      This program is distributed in the hope that it will be
  20      useful, but WITHOUT ANY WARRANTY; without even the implied
  21      warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
  22      See the GNU General Public License for more details.
  23    </para>
  24
  25    <para>
  26      You should have received a copy of the GNU General Public
  27      License along with this program; if not, write to the Free
  28      Software Foundation, Inc., 59 Temple Place, Suite 330, Boston,
  29      MA 02111-1307 USA
  30    </para>
  31
  32    <para>
  33      For more details see the file COPYING in the source
  34      distribution of Linux.
  35    </para>
  36   </legalnotice>
  37  </bookinfo>
  38
  39 <toc></toc>
  40
  41   <chapter id="Basics">
  42      <title>Driver Basics</title>
  43      <sect1><title>Driver Entry and Exit points</title>
  44 !Iinclude/linux/init.h
  45      </sect1>
  46
  47      <sect1><title>Atomic and pointer manipulation</title>
  48 !Iarch/x86/include/asm/atomic.h
  49      </sect1>
  50
  51      <sect1><title>Delaying, scheduling, and timer routines</title>
  52 !Iinclude/linux/sched.h
  53 !Ekernel/sched/core.c
  54 !Ikernel/sched/cpupri.c
  55 !Ikernel/sched/fair.c
  56 !Iinclude/linux/completion.h
  57 !Ekernel/time/timer.c
  58      </sect1>
  59      <sect1><title>Wait queues and Wake events</title>
  60 !Iinclude/linux/wait.h
  61 !Ekernel/sched/wait.c
  62      </sect1>
  63      <sect1><title>High-resolution timers</title>
  64 !Iinclude/linux/ktime.h
  65 !Iinclude/linux/hrtimer.h
  66 !Ekernel/time/hrtimer.c
  67      </sect1>
  68      <sect1><title>Workqueues and Kevents</title>
  69 !Iinclude/linux/workqueue.h
  70 !Ekernel/workqueue.c
  71      </sect1>
  72      <sect1><title>Internal Functions</title>
  73 !Ikernel/exit.c
  74 !Ikernel/signal.c
  75 !Iinclude/linux/kthread.h
  76 !Ekernel/kthread.c
  77      </sect1>
  78
  79      <sect1><title>Kernel objects manipulation</title>
  80 <!--
  81 X!Iinclude/linux/kobject.h
  82 -->
  83 !Elib/kobject.c
  84      </sect1>
  85
  86      <sect1><title>Kernel utility functions</title>
  87 !Iinclude/linux/kernel.h
  88 !Ekernel/printk/printk.c
  89 !Ekernel/panic.c
  90 !Ekernel/sys.c
  91 !Ekernel/rcu/srcu.c
  92 !Ekernel/rcu/tree.c
  93 !Ekernel/rcu/tree_plugin.h
  94 !Ekernel/rcu/update.c
  95      </sect1>
  96
  97      <sect1><title>Device Resource Management</title>
  98 !Edrivers/base/devres.c
  99      </sect1>
 100
 101   </chapter>
 102
 103   <chapter id="devdrivers">
 104      <title>Device drivers infrastructure</title>
 105      <sect1><title>The Basic Device Driver-Model Structures </title>
 106 !Iinclude/linux/device.h
 107      </sect1>
 108      <sect1><title>Device Drivers Base</title>
 109 !Idrivers/base/init.c
 110 !Edrivers/base/driver.c
 111 !Edrivers/base/core.c
 112 !Edrivers/base/syscore.c
 113 !Edrivers/base/class.c
 114 !Idrivers/base/node.c
 115 !Edrivers/base/firmware_class.c
 116 !Edrivers/base/transport_class.c
 117 <!-- Cannot be included, because
 118      attribute_container_add_class_device_adapter
 119  and attribute_container_classdev_to_container
 120      exceed allowed 44 characters maximum
 121 X!Edrivers/base/attribute_container.c
 122 -->
 123 !Edrivers/base/dd.c
 124 <!--
 125 X!Edrivers/base/interface.c
 126 -->
 127 !Iinclude/linux/platform_device.h
 128 !Edrivers/base/platform.c
 129 !Edrivers/base/bus.c
 130      </sect1>
 131      <sect1><title>Device Drivers DMA Management</title>
 132 !Edrivers/dma-buf/dma-buf.c
 133 !Edrivers/dma-buf/fence.c
 134 !Edrivers/dma-buf/seqno-fence.c
 135 !Iinclude/linux/fence.h
 136 !Iinclude/linux/seqno-fence.h
 137 !Edrivers/dma-buf/reservation.c
 138 !Iinclude/linux/reservation.h
 139 !Edrivers/base/dma-coherent.c
 140 !Edrivers/base/dma-mapping.c
 141      </sect1>
 142      <sect1><title>Device Drivers Power Management</title>
 143 !Edrivers/base/power/main.c
 144      </sect1>
 145      <sect1><title>Device Drivers ACPI Support</title>
 146 <!-- Internal functions only
 147 X!Edrivers/acpi/sleep/main.c
 148 X!Edrivers/acpi/sleep/wakeup.c
 149 X!Edrivers/acpi/motherboard.c
 150 X!Edrivers/acpi/bus.c
 151 -->
 152 !Edrivers/acpi/scan.c
 153 !Idrivers/acpi/scan.c
 154 <!-- No correct structured comments
 155 X!Edrivers/acpi/pci_bind.c
 156 -->
 157      </sect1>
 158      <sect1><title>Device drivers PnP support</title>
 159 !Idrivers/pnp/core.c
 160 <!-- No correct structured comments
 161 X!Edrivers/pnp/system.c
 162  -->
 163 !Edrivers/pnp/card.c
 164 !Idrivers/pnp/driver.c
 165 !Edrivers/pnp/manager.c
 166 !Edrivers/pnp/support.c
 167      </sect1>
 168      <sect1><title>Userspace IO devices</title>
 169 !Edrivers/uio/uio.c
 170 !Iinclude/linux/uio_driver.h
 171      </sect1>
 172   </chapter>
 173
 174   <chapter id="parportdev">
 175      <title>Parallel Port Devices</title>
 176 !Iinclude/linux/parport.h
 177 !Edrivers/parport/ieee1284.c
 178 !Edrivers/parport/share.c
 179 !Idrivers/parport/daisy.c
 180   </chapter>
 181
 182   <chapter id="message_devices">
 183         <title>Message-based devices</title>
 184      <sect1><title>Fusion message devices</title>
 185 !Edrivers/message/fusion/mptbase.c
 186 !Idrivers/message/fusion/mptbase.c
 187 !Edrivers/message/fusion/mptscsih.c
 188 !Idrivers/message/fusion/mptscsih.c
 189 !Idrivers/message/fusion/mptctl.c
 190 !Idrivers/message/fusion/mptspi.c
 191 !Idrivers/message/fusion/mptfc.c
 192 !Idrivers/message/fusion/mptlan.c
 193      </sect1>
 194   </chapter>
 195
 196   <chapter id="snddev">
 197      <title>Sound Devices</title>
 198 !Iinclude/sound/core.h
 199 !Esound/sound_core.c
 200 !Iinclude/sound/pcm.h
 201 !Esound/core/pcm.c
 202 !Esound/core/device.c
 203 !Esound/core/info.c
 204 !Esound/core/rawmidi.c
 205 !Esound/core/sound.c
 206 !Esound/core/memory.c
 207 !Esound/core/pcm_memory.c
 208 !Esound/core/init.c
 209 !Esound/core/isadma.c
 210 !Esound/core/control.c
 211 !Esound/core/pcm_lib.c
 212 !Esound/core/hwdep.c
 213 !Esound/core/pcm_native.c
 214 !Esound/core/memalloc.c
 215 <!-- FIXME: Removed for now since no structured comments in source
 216 X!Isound/sound_firmware.c
 217 -->
 218   </chapter>
 219
 220   <chapter id="mediadev">
 221      <title>Media Devices</title>
 222
 223      <sect1><title>Video2Linux devices</title>
 224 !Iinclude/media/v4l2-async.h
 225 !Iinclude/media/v4l2-ctrls.h
 226 !Iinclude/media/v4l2-dv-timings.h
 227 !Iinclude/media/v4l2-event.h
 228 !Iinclude/media/v4l2-flash-led-class.h
 229 !Iinclude/media/v4l2-mediabus.h
 230 !Iinclude/media/v4l2-mem2mem.h
 231 !Iinclude/media/v4l2-of.h
 232 !Iinclude/media/v4l2-subdev.h
 233 !Iinclude/media/videobuf2-core.h
 234 !Iinclude/media/videobuf2-memops.h
 235      </sect1>
 236      <sect1><title>Digital TV (DVB) devices</title>
 237 !Idrivers/media/dvb-core/dvb_ca_en50221.h
 238 !Idrivers/media/dvb-core/dvb_frontend.h
 239 !Idrivers/media/dvb-core/dvb_math.h
 240 !Idrivers/media/dvb-core/dvb_ringbuffer.h
 241 !Idrivers/media/dvb-core/dvbdev.h
 242      </sect1>
 243      <sect1><title>Remote Controller devices</title>
 244 !Iinclude/media/rc-core.h
 245      </sect1>
 246      <sect1><title>Media Controller devices</title>
 247 !Iinclude/media/media-device.h
 248 !Iinclude/media/media-devnode.h
 249 !Iinclude/media/media-entity.h
 250      </sect1>
 251
 252   </chapter>
 253
 254   <chapter id="uart16x50">
 255      <title>16x50 UART Driver</title>
 256 !Edrivers/tty/serial/serial_core.c
 257 !Edrivers/tty/serial/8250/8250_core.c
 258   </chapter>
 259
 260   <chapter id="fbdev">
 261      <title>Frame Buffer Library</title>
 262
 263      <para>
 264        The frame buffer drivers depend heavily on four data structures.
 265        These structures are declared in include/linux/fb.h.  They are
 266        fb_info, fb_var_screeninfo, fb_fix_screeninfo and fb_monospecs.
 267        The last three can be made available to and from userland.
 268      </para>
 269
 270      <para>
 271        fb_info defines the current state of a particular video card.
 272        Inside fb_info, there exists a fb_ops structure which is a
 273        collection of needed functions to make fbdev and fbcon work.
 274        fb_info is only visible to the kernel.
 275      </para>
 276
 277      <para>
 278        fb_var_screeninfo is used to describe the features of a video card
 279        that are user defined.  With fb_var_screeninfo, things such as
 280        depth and the resolution may be defined.
 281      </para>
 282
 283      <para>
 284        The next structure is fb_fix_screeninfo. This defines the
 285        properties of a card that are created when a mode is set and can't
 286        be changed otherwise.  A good example of this is the start of the
 287        frame buffer memory.  This "locks" the address of the frame buffer
 288        memory, so that it cannot be changed or moved.
 289      </para>
 290
 291      <para>
 292        The last structure is fb_monospecs. In the old API, there was
 293        little importance for fb_monospecs. This allowed for forbidden things
 294        such as setting a mode of 800x600 on a fix frequency monitor. With
 295        the new API, fb_monospecs prevents such things, and if used
 296        correctly, can prevent a monitor from being cooked.  fb_monospecs
 297        will not be useful until kernels 2.5.x.
 298      </para>
 299
 300      <sect1><title>Frame Buffer Memory</title>
 301 !Edrivers/video/fbdev/core/fbmem.c
 302      </sect1>
 303 <!--
 304      <sect1><title>Frame Buffer Console</title>
 305 X!Edrivers/video/console/fbcon.c
 306      </sect1>
 307 -->
 308      <sect1><title>Frame Buffer Colormap</title>
 309 !Edrivers/video/fbdev/core/fbcmap.c
 310      </sect1>
 311 <!-- FIXME:
 312   drivers/video/fbgen.c has no docs, which stuffs up the sgml.  Comment
 313   out until somebody adds docs.  KAO
 314      <sect1><title>Frame Buffer Generic Functions</title>
 315 X!Idrivers/video/fbgen.c
 316      </sect1>
 317 KAO -->
 318      <sect1><title>Frame Buffer Video Mode Database</title>
 319 !Idrivers/video/fbdev/core/modedb.c
 320 !Edrivers/video/fbdev/core/modedb.c
 321      </sect1>
 322      <sect1><title>Frame Buffer Macintosh Video Mode Database</title>
 323 !Edrivers/video/fbdev/macmodes.c
 324      </sect1>
 325      <sect1><title>Frame Buffer Fonts</title>
 326         <para>
 327            Refer to the file lib/fonts/fonts.c for more information.
 328         </para>
 329 <!-- FIXME: Removed for now since no structured comments in source
 330 X!Ilib/fonts/fonts.c
 331 -->
 332      </sect1>
 333   </chapter>
 334
 335   <chapter id="input_subsystem">
 336      <title>Input Subsystem</title>
 337      <sect1><title>Input core</title>
 338 !Iinclude/linux/input.h
 339 !Edrivers/input/input.c
 340 !Edrivers/input/ff-core.c
 341 !Edrivers/input/ff-memless.c
 342      </sect1>
 343      <sect1><title>Multitouch Library</title>
 344 !Iinclude/linux/input/mt.h
 345 !Edrivers/input/input-mt.c
 346      </sect1>
 347      <sect1><title>Polled input devices</title>
 348 !Iinclude/linux/input-polldev.h
 349 !Edrivers/input/input-polldev.c
 350      </sect1>
 351      <sect1><title>Matrix keyboars/keypads</title>
 352 !Iinclude/linux/input/matrix_keypad.h
 353      </sect1>
 354      <sect1><title>Sparse keymap support</title>
 355 !Iinclude/linux/input/sparse-keymap.h
 356 !Edrivers/input/sparse-keymap.c
 357      </sect1>
 358   </chapter>
 359
 360   <chapter id="spi">
 361       <title>Serial Peripheral Interface (SPI)</title>
 362   <para>
 363         SPI is the "Serial Peripheral Interface", widely used with
 364         embedded systems because it is a simple and efficient
 365         interface:  basically a multiplexed shift register.
 366         Its three signal wires hold a clock (SCK, often in the range
 367         of 1-20 MHz), a "Master Out, Slave In" (MOSI) data line, and
 368         a "Master In, Slave Out" (MISO) data line.
 369         SPI is a full duplex protocol; for each bit shifted out the
 370         MOSI line (one per clock) another is shifted in on the MISO line.
 371         Those bits are assembled into words of various sizes on the
 372         way to and from system memory.
 373         An additional chipselect line is usually active-low (nCS);
 374         four signals are normally used for each peripheral, plus
 375         sometimes an interrupt.
 376   </para>
 377   <para>
 378         The SPI bus facilities listed here provide a generalized
 379         interface to declare SPI busses and devices, manage them
 380         according to the standard Linux driver model, and perform
 381         input/output operations.
 382         At this time, only "master" side interfaces are supported,
 383         where Linux talks to SPI peripherals and does not implement
 384         such a peripheral itself.
 385         (Interfaces to support implementing SPI slaves would
 386         necessarily look different.)
 387   </para>
 388   <para>
 389         The programming interface is structured around two kinds of driver,
 390         and two kinds of device.
 391         A "Controller Driver" abstracts the controller hardware, which may
 392         be as simple as a set of GPIO pins or as complex as a pair of FIFOs
 393         connected to dual DMA engines on the other side of the SPI shift
 394         register (maximizing throughput).  Such drivers bridge between
 395         whatever bus they sit on (often the platform bus) and SPI, and
 396         expose the SPI side of their device as a
 397         <structname>struct spi_master</structname>.
 398         SPI devices are children of that master, represented as a
 399         <structname>struct spi_device</structname> and manufactured from
 400         <structname>struct spi_board_info</structname> descriptors which
 401         are usually provided by board-specific initialization code.
 402         A <structname>struct spi_driver</structname> is called a
 403         "Protocol Driver", and is bound to a spi_device using normal
 404         driver model calls.
 405   </para>
 406   <para>
 407         The I/O model is a set of queued messages.  Protocol drivers
 408         submit one or more <structname>struct spi_message</structname>
 409         objects, which are processed and completed asynchronously.
 410         (There are synchronous wrappers, however.)  Messages are
 411         built from one or more <structname>struct spi_transfer</structname>
 412         objects, each of which wraps a full duplex SPI transfer.
 413         A variety of protocol tweaking options are needed, because
 414         different chips adopt very different policies for how they
 415         use the bits transferred with SPI.
 416   </para>
 417 !Iinclude/linux/spi/spi.h
 418 !Fdrivers/spi/spi.c spi_register_board_info
 419 !Edrivers/spi/spi.c
 420   </chapter>
 421
 422   <chapter id="i2c">
 423      <title>I<superscript>2</superscript>C and SMBus Subsystem</title>
 424
 425      <para>
 426         I<superscript>2</superscript>C (or without fancy typography, "I2C")
 427         is an acronym for the "Inter-IC" bus, a simple bus protocol which is
 428         widely used where low data rate communications suffice.
 429         Since it's also a licensed trademark, some vendors use another
 430         name (such as "Two-Wire Interface", TWI) for the same bus.
 431         I2C only needs two signals (SCL for clock, SDA for data), conserving
 432         board real estate and minimizing signal quality issues.
 433         Most I2C devices use seven bit addresses, and bus speeds of up
 434         to 400 kHz; there's a high speed extension (3.4 MHz) that's not yet
 435         found wide use.
 436         I2C is a multi-master bus; open drain signaling is used to
 437         arbitrate between masters, as well as to handshake and to
 438         synchronize clocks from slower clients.
 439      </para>
 440
 441      <para>
 442         The Linux I2C programming interfaces support only the master
 443         side of bus interactions, not the slave side.
 444         The programming interface is structured around two kinds of driver,
 445         and two kinds of device.
 446         An I2C "Adapter Driver" abstracts the controller hardware; it binds
 447         to a physical device (perhaps a PCI device or platform_device) and
 448         exposes a <structname>struct i2c_adapter</structname> representing
 449         each I2C bus segment it manages.
 450         On each I2C bus segment will be I2C devices represented by a
 451         <structname>struct i2c_client</structname>.  Those devices will
 452         be bound to a <structname>struct i2c_driver</structname>,
 453         which should follow the standard Linux driver model.
 454         (At this writing, a legacy model is more widely used.)
 455         There are functions to perform various I2C protocol operations; at
 456         this writing all such functions are usable only from task context.
 457      </para>
 458
 459      <para>
 460         The System Management Bus (SMBus) is a sibling protocol.  Most SMBus
 461         systems are also I2C conformant.  The electrical constraints are
 462         tighter for SMBus, and it standardizes particular protocol messages
 463         and idioms.  Controllers that support I2C can also support most
 464         SMBus operations, but SMBus controllers don't support all the protocol
 465         options that an I2C controller will.
 466         There are functions to perform various SMBus protocol operations,
 467         either using I2C primitives or by issuing SMBus commands to
 468         i2c_adapter devices which don't support those I2C operations.
 469      </para>
 470
 471 !Iinclude/linux/i2c.h
 472 !Fdrivers/i2c/i2c-boardinfo.c i2c_register_board_info
 473 !Edrivers/i2c/i2c-core.c
 474   </chapter>
 475
 476   <chapter id="hsi">
 477      <title>High Speed Synchronous Serial Interface (HSI)</title>
 478
 479      <para>
 480         High Speed Synchronous Serial Interface (HSI) is a
 481         serial interface mainly used for connecting application
 482         engines (APE) with cellular modem engines (CMT) in cellular
 483         handsets.
 484
 485         HSI provides multiplexing for up to 16 logical channels,
 486         low-latency and full duplex communication.
 487      </para>
 488
 489 !Iinclude/linux/hsi/hsi.h
 490 !Edrivers/hsi/hsi.c
 491   </chapter>
 492
 493   <chapter id="pwm">
 494     <title>Pulse-Width Modulation (PWM)</title>
 495     <para>
 496       Pulse-width modulation is a modulation technique primarily used to
 497       control power supplied to electrical devices.
 498     </para>
 499     <para>
 500       The PWM framework provides an abstraction for providers and consumers
 501       of PWM signals. A controller that provides one or more PWM signals is
 502       registered as <structname>struct pwm_chip</structname>. Providers are
 503       expected to embed this structure in a driver-specific structure. This
 504       structure contains fields that describe a particular chip.
 505     </para>
 506     <para>
 507       A chip exposes one or more PWM signal sources, each of which exposed
 508       as a <structname>struct pwm_device</structname>. Operations can be
 509       performed on PWM devices to control the period, duty cycle, polarity
 510       and active state of the signal.
 511     </para>
 512     <para>
 513       Note that PWM devices are exclusive resources: they can always only be
 514       used by one consumer at a time.
 515     </para>
 516 !Iinclude/linux/pwm.h
 517 !Edrivers/pwm/core.c
 518   </chapter>
 519
 520 </book>