Documentation/DocBook/device-drivers.tmpl

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   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/tuner.h
 225 !Iinclude/media/tuner-types.h
 226 !Iinclude/media/tveeprom.h
 227 !Iinclude/media/v4l2-async.h
 228 !Iinclude/media/v4l2-ctrls.h
 229 !Iinclude/media/v4l2-dv-timings.h
 230 !Iinclude/media/v4l2-event.h
 231 !Iinclude/media/v4l2-flash-led-class.h
 232 !Iinclude/media/v4l2-mediabus.h
 233 !Iinclude/media/v4l2-mem2mem.h
 234 !Iinclude/media/v4l2-of.h
 235 !Iinclude/media/v4l2-subdev.h
 236 !Iinclude/media/videobuf2-core.h
 237 !Iinclude/media/videobuf2-v4l2.h
 238 !Iinclude/media/videobuf2-memops.h
 239      </sect1>
 240      <sect1><title>Digital TV (DVB) devices</title>
 241         <sect1><title>Digital TV Common functions</title>
 242 !Idrivers/media/dvb-core/dvb_math.h
 243 !Idrivers/media/dvb-core/dvb_ringbuffer.h
 244 !Idrivers/media/dvb-core/dvbdev.h
 245         </sect1>
 246         <sect1><title>Digital TV Frontend kABI</title>
 247 !Pdrivers/media/dvb-core/dvb_frontend.h Digital TV Frontend
 248 !Idrivers/media/dvb-core/dvb_frontend.h
 249         </sect1>
 250         <sect1><title>Digital TV Demux kABI</title>
 251 !Pdrivers/media/dvb-core/demux.h Digital TV Demux
 252         <sect1><title>Demux Callback API</title>
 253 !Pdrivers/media/dvb-core/demux.h Demux Callback
 254         </sect1>
 255 !Idrivers/media/dvb-core/demux.h
 256         </sect1>
 257         <sect1><title>Digital TV Conditional Access kABI</title>
 258 !Idrivers/media/dvb-core/dvb_ca_en50221.h
 259         </sect1>
 260      </sect1>
 261     <sect1><title>Remote Controller devices</title>
 262 !Iinclude/media/rc-core.h
 263 !Iinclude/media/lirc_dev.h
 264     </sect1>
 265     <sect1><title>Media Controller devices</title>
 266 !Pinclude/media/media-device.h Media Controller
 267 !Iinclude/media/media-device.h
 268 !Iinclude/media/media-devnode.h
 269 !Iinclude/media/media-entity.h
 270     </sect1>
 271
 272   </chapter>
 273
 274   <chapter id="uart16x50">
 275      <title>16x50 UART Driver</title>
 276 !Edrivers/tty/serial/serial_core.c
 277 !Edrivers/tty/serial/8250/8250_core.c
 278   </chapter>
 279
 280   <chapter id="fbdev">
 281      <title>Frame Buffer Library</title>
 282
 283      <para>
 284        The frame buffer drivers depend heavily on four data structures.
 285        These structures are declared in include/linux/fb.h.  They are
 286        fb_info, fb_var_screeninfo, fb_fix_screeninfo and fb_monospecs.
 287        The last three can be made available to and from userland.
 288      </para>
 289
 290      <para>
 291        fb_info defines the current state of a particular video card.
 292        Inside fb_info, there exists a fb_ops structure which is a
 293        collection of needed functions to make fbdev and fbcon work.
 294        fb_info is only visible to the kernel.
 295      </para>
 296
 297      <para>
 298        fb_var_screeninfo is used to describe the features of a video card
 299        that are user defined.  With fb_var_screeninfo, things such as
 300        depth and the resolution may be defined.
 301      </para>
 302
 303      <para>
 304        The next structure is fb_fix_screeninfo. This defines the
 305        properties of a card that are created when a mode is set and can't
 306        be changed otherwise.  A good example of this is the start of the
 307        frame buffer memory.  This "locks" the address of the frame buffer
 308        memory, so that it cannot be changed or moved.
 309      </para>
 310
 311      <para>
 312        The last structure is fb_monospecs. In the old API, there was
 313        little importance for fb_monospecs. This allowed for forbidden things
 314        such as setting a mode of 800x600 on a fix frequency monitor. With
 315        the new API, fb_monospecs prevents such things, and if used
 316        correctly, can prevent a monitor from being cooked.  fb_monospecs
 317        will not be useful until kernels 2.5.x.
 318      </para>
 319
 320      <sect1><title>Frame Buffer Memory</title>
 321 !Edrivers/video/fbdev/core/fbmem.c
 322      </sect1>
 323 <!--
 324      <sect1><title>Frame Buffer Console</title>
 325 X!Edrivers/video/console/fbcon.c
 326      </sect1>
 327 -->
 328      <sect1><title>Frame Buffer Colormap</title>
 329 !Edrivers/video/fbdev/core/fbcmap.c
 330      </sect1>
 331 <!-- FIXME:
 332   drivers/video/fbgen.c has no docs, which stuffs up the sgml.  Comment
 333   out until somebody adds docs.  KAO
 334      <sect1><title>Frame Buffer Generic Functions</title>
 335 X!Idrivers/video/fbgen.c
 336      </sect1>
 337 KAO -->
 338      <sect1><title>Frame Buffer Video Mode Database</title>
 339 !Idrivers/video/fbdev/core/modedb.c
 340 !Edrivers/video/fbdev/core/modedb.c
 341      </sect1>
 342      <sect1><title>Frame Buffer Macintosh Video Mode Database</title>
 343 !Edrivers/video/fbdev/macmodes.c
 344      </sect1>
 345      <sect1><title>Frame Buffer Fonts</title>
 346         <para>
 347            Refer to the file lib/fonts/fonts.c for more information.
 348         </para>
 349 <!-- FIXME: Removed for now since no structured comments in source
 350 X!Ilib/fonts/fonts.c
 351 -->
 352      </sect1>
 353   </chapter>
 354
 355   <chapter id="input_subsystem">
 356      <title>Input Subsystem</title>
 357      <sect1><title>Input core</title>
 358 !Iinclude/linux/input.h
 359 !Edrivers/input/input.c
 360 !Edrivers/input/ff-core.c
 361 !Edrivers/input/ff-memless.c
 362      </sect1>
 363      <sect1><title>Multitouch Library</title>
 364 !Iinclude/linux/input/mt.h
 365 !Edrivers/input/input-mt.c
 366      </sect1>
 367      <sect1><title>Polled input devices</title>
 368 !Iinclude/linux/input-polldev.h
 369 !Edrivers/input/input-polldev.c
 370      </sect1>
 371      <sect1><title>Matrix keyboars/keypads</title>
 372 !Iinclude/linux/input/matrix_keypad.h
 373      </sect1>
 374      <sect1><title>Sparse keymap support</title>
 375 !Iinclude/linux/input/sparse-keymap.h
 376 !Edrivers/input/sparse-keymap.c
 377      </sect1>
 378   </chapter>
 379
 380   <chapter id="spi">
 381       <title>Serial Peripheral Interface (SPI)</title>
 382   <para>
 383         SPI is the "Serial Peripheral Interface", widely used with
 384         embedded systems because it is a simple and efficient
 385         interface:  basically a multiplexed shift register.
 386         Its three signal wires hold a clock (SCK, often in the range
 387         of 1-20 MHz), a "Master Out, Slave In" (MOSI) data line, and
 388         a "Master In, Slave Out" (MISO) data line.
 389         SPI is a full duplex protocol; for each bit shifted out the
 390         MOSI line (one per clock) another is shifted in on the MISO line.
 391         Those bits are assembled into words of various sizes on the
 392         way to and from system memory.
 393         An additional chipselect line is usually active-low (nCS);
 394         four signals are normally used for each peripheral, plus
 395         sometimes an interrupt.
 396   </para>
 397   <para>
 398         The SPI bus facilities listed here provide a generalized
 399         interface to declare SPI busses and devices, manage them
 400         according to the standard Linux driver model, and perform
 401         input/output operations.
 402         At this time, only "master" side interfaces are supported,
 403         where Linux talks to SPI peripherals and does not implement
 404         such a peripheral itself.
 405         (Interfaces to support implementing SPI slaves would
 406         necessarily look different.)
 407   </para>
 408   <para>
 409         The programming interface is structured around two kinds of driver,
 410         and two kinds of device.
 411         A "Controller Driver" abstracts the controller hardware, which may
 412         be as simple as a set of GPIO pins or as complex as a pair of FIFOs
 413         connected to dual DMA engines on the other side of the SPI shift
 414         register (maximizing throughput).  Such drivers bridge between
 415         whatever bus they sit on (often the platform bus) and SPI, and
 416         expose the SPI side of their device as a
 417         <structname>struct spi_master</structname>.
 418         SPI devices are children of that master, represented as a
 419         <structname>struct spi_device</structname> and manufactured from
 420         <structname>struct spi_board_info</structname> descriptors which
 421         are usually provided by board-specific initialization code.
 422         A <structname>struct spi_driver</structname> is called a
 423         "Protocol Driver", and is bound to a spi_device using normal
 424         driver model calls.
 425   </para>
 426   <para>
 427         The I/O model is a set of queued messages.  Protocol drivers
 428         submit one or more <structname>struct spi_message</structname>
 429         objects, which are processed and completed asynchronously.
 430         (There are synchronous wrappers, however.)  Messages are
 431         built from one or more <structname>struct spi_transfer</structname>
 432         objects, each of which wraps a full duplex SPI transfer.
 433         A variety of protocol tweaking options are needed, because
 434         different chips adopt very different policies for how they
 435         use the bits transferred with SPI.
 436   </para>
 437 !Iinclude/linux/spi/spi.h
 438 !Fdrivers/spi/spi.c spi_register_board_info
 439 !Edrivers/spi/spi.c
 440   </chapter>
 441
 442   <chapter id="i2c">
 443      <title>I<superscript>2</superscript>C and SMBus Subsystem</title>
 444
 445      <para>
 446         I<superscript>2</superscript>C (or without fancy typography, "I2C")
 447         is an acronym for the "Inter-IC" bus, a simple bus protocol which is
 448         widely used where low data rate communications suffice.
 449         Since it's also a licensed trademark, some vendors use another
 450         name (such as "Two-Wire Interface", TWI) for the same bus.
 451         I2C only needs two signals (SCL for clock, SDA for data), conserving
 452         board real estate and minimizing signal quality issues.
 453         Most I2C devices use seven bit addresses, and bus speeds of up
 454         to 400 kHz; there's a high speed extension (3.4 MHz) that's not yet
 455         found wide use.
 456         I2C is a multi-master bus; open drain signaling is used to
 457         arbitrate between masters, as well as to handshake and to
 458         synchronize clocks from slower clients.
 459      </para>
 460
 461      <para>
 462         The Linux I2C programming interfaces support only the master
 463         side of bus interactions, not the slave side.
 464         The programming interface is structured around two kinds of driver,
 465         and two kinds of device.
 466         An I2C "Adapter Driver" abstracts the controller hardware; it binds
 467         to a physical device (perhaps a PCI device or platform_device) and
 468         exposes a <structname>struct i2c_adapter</structname> representing
 469         each I2C bus segment it manages.
 470         On each I2C bus segment will be I2C devices represented by a
 471         <structname>struct i2c_client</structname>.  Those devices will
 472         be bound to a <structname>struct i2c_driver</structname>,
 473         which should follow the standard Linux driver model.
 474         (At this writing, a legacy model is more widely used.)
 475         There are functions to perform various I2C protocol operations; at
 476         this writing all such functions are usable only from task context.
 477      </para>
 478
 479      <para>
 480         The System Management Bus (SMBus) is a sibling protocol.  Most SMBus
 481         systems are also I2C conformant.  The electrical constraints are
 482         tighter for SMBus, and it standardizes particular protocol messages
 483         and idioms.  Controllers that support I2C can also support most
 484         SMBus operations, but SMBus controllers don't support all the protocol
 485         options that an I2C controller will.
 486         There are functions to perform various SMBus protocol operations,
 487         either using I2C primitives or by issuing SMBus commands to
 488         i2c_adapter devices which don't support those I2C operations.
 489      </para>
 490
 491 !Iinclude/linux/i2c.h
 492 !Fdrivers/i2c/i2c-boardinfo.c i2c_register_board_info
 493 !Edrivers/i2c/i2c-core.c
 494   </chapter>
 495
 496   <chapter id="hsi">
 497      <title>High Speed Synchronous Serial Interface (HSI)</title>
 498
 499      <para>
 500         High Speed Synchronous Serial Interface (HSI) is a
 501         serial interface mainly used for connecting application
 502         engines (APE) with cellular modem engines (CMT) in cellular
 503         handsets.
 504
 505         HSI provides multiplexing for up to 16 logical channels,
 506         low-latency and full duplex communication.
 507      </para>
 508
 509 !Iinclude/linux/hsi/hsi.h
 510 !Edrivers/hsi/hsi.c
 511   </chapter>
 512
 513   <chapter id="pwm">
 514     <title>Pulse-Width Modulation (PWM)</title>
 515     <para>
 516       Pulse-width modulation is a modulation technique primarily used to
 517       control power supplied to electrical devices.
 518     </para>
 519     <para>
 520       The PWM framework provides an abstraction for providers and consumers
 521       of PWM signals. A controller that provides one or more PWM signals is
 522       registered as <structname>struct pwm_chip</structname>. Providers are
 523       expected to embed this structure in a driver-specific structure. This
 524       structure contains fields that describe a particular chip.
 525     </para>
 526     <para>
 527       A chip exposes one or more PWM signal sources, each of which exposed
 528       as a <structname>struct pwm_device</structname>. Operations can be
 529       performed on PWM devices to control the period, duty cycle, polarity
 530       and active state of the signal.
 531     </para>
 532     <para>
 533       Note that PWM devices are exclusive resources: they can always only be
 534       used by one consumer at a time.
 535     </para>
 536 !Iinclude/linux/pwm.h
 537 !Edrivers/pwm/core.c
 538   </chapter>
 539
 540 </book>