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1<?xml version="1.0" encoding="UTF-8"?>
2<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
3 "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" []>
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<!--
81X!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
121X!Edrivers/base/attribute_container.c
122-->
123!Edrivers/base/dd.c
124<!--
125X!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>
132 <title>Buffer Sharing and Synchronization</title>
133 <para>
134 The dma-buf subsystem provides the framework for sharing buffers
135 for hardware (DMA) access across multiple device drivers and
136 subsystems, and for synchronizing asynchronous hardware access.
137 </para>
138 <para>
139 This is used, for example, by drm "prime" multi-GPU support, but
140 is of course not limited to GPU use cases.
141 </para>
142 <para>
143 The three main components of this are: (1) dma-buf, representing
144 a sg_table and exposed to userspace as a file descriptor to allow
145 passing between devices, (2) fence, which provides a mechanism
146 to signal when one device as finished access, and (3) reservation,
147 which manages the shared or exclusive fence(s) associated with
148 the buffer.
149 </para>
150 <sect2><title>dma-buf</title>
151!Edrivers/dma-buf/dma-buf.c
152!Iinclude/linux/dma-buf.h
153 </sect2>
154 <sect2><title>reservation</title>
155!Pdrivers/dma-buf/reservation.c Reservation Object Overview
156!Edrivers/dma-buf/reservation.c
157!Iinclude/linux/reservation.h
158 </sect2>
159 <sect2><title>fence</title>
160!Edrivers/dma-buf/fence.c
161!Iinclude/linux/fence.h
162!Edrivers/dma-buf/seqno-fence.c
163!Iinclude/linux/seqno-fence.h
164!Edrivers/dma-buf/sync_file.c
165!Iinclude/linux/sync_file.h
166 </sect2>
167 </sect1>
168 <sect1><title>Device Drivers DMA Management</title>
169!Edrivers/base/dma-coherent.c
170!Edrivers/base/dma-mapping.c
171 </sect1>
172 <sect1><title>Device Drivers Power Management</title>
173!Edrivers/base/power/main.c
174 </sect1>
175 <sect1><title>Device Drivers ACPI Support</title>
176<!-- Internal functions only
177X!Edrivers/acpi/sleep/main.c
178X!Edrivers/acpi/sleep/wakeup.c
179X!Edrivers/acpi/motherboard.c
180X!Edrivers/acpi/bus.c
181-->
182!Edrivers/acpi/scan.c
183!Idrivers/acpi/scan.c
184<!-- No correct structured comments
185X!Edrivers/acpi/pci_bind.c
186-->
187 </sect1>
188 <sect1><title>Device drivers PnP support</title>
189!Idrivers/pnp/core.c
190<!-- No correct structured comments
191X!Edrivers/pnp/system.c
192 -->
193!Edrivers/pnp/card.c
194!Idrivers/pnp/driver.c
195!Edrivers/pnp/manager.c
196!Edrivers/pnp/support.c
197 </sect1>
198 <sect1><title>Userspace IO devices</title>
199!Edrivers/uio/uio.c
200!Iinclude/linux/uio_driver.h
201 </sect1>
202 </chapter>
203
204 <chapter id="parportdev">
205 <title>Parallel Port Devices</title>
206!Iinclude/linux/parport.h
207!Edrivers/parport/ieee1284.c
208!Edrivers/parport/share.c
209!Idrivers/parport/daisy.c
210 </chapter>
211
212 <chapter id="message_devices">
213 <title>Message-based devices</title>
214 <sect1><title>Fusion message devices</title>
215!Edrivers/message/fusion/mptbase.c
216!Idrivers/message/fusion/mptbase.c
217!Edrivers/message/fusion/mptscsih.c
218!Idrivers/message/fusion/mptscsih.c
219!Idrivers/message/fusion/mptctl.c
220!Idrivers/message/fusion/mptspi.c
221!Idrivers/message/fusion/mptfc.c
222!Idrivers/message/fusion/mptlan.c
223 </sect1>
224 </chapter>
225
226 <chapter id="snddev">
227 <title>Sound Devices</title>
228!Iinclude/sound/core.h
229!Esound/sound_core.c
230!Iinclude/sound/pcm.h
231!Esound/core/pcm.c
232!Esound/core/device.c
233!Esound/core/info.c
234!Esound/core/rawmidi.c
235!Esound/core/sound.c
236!Esound/core/memory.c
237!Esound/core/pcm_memory.c
238!Esound/core/init.c
239!Esound/core/isadma.c
240!Esound/core/control.c
241!Esound/core/pcm_lib.c
242!Esound/core/hwdep.c
243!Esound/core/pcm_native.c
244!Esound/core/memalloc.c
245<!-- FIXME: Removed for now since no structured comments in source
246X!Isound/sound_firmware.c
247-->
248 </chapter>
249
250 <chapter id="mediadev">
251 <title>Media Devices</title>
252
253 <sect1><title>Video2Linux devices</title>
254!Iinclude/media/tuner.h
255!Iinclude/media/tuner-types.h
256!Iinclude/media/tveeprom.h
257!Iinclude/media/v4l2-async.h
258!Iinclude/media/v4l2-ctrls.h
259!Iinclude/media/v4l2-dv-timings.h
260!Iinclude/media/v4l2-event.h
261!Iinclude/media/v4l2-flash-led-class.h
262!Iinclude/media/v4l2-mc.h
263!Iinclude/media/v4l2-mediabus.h
264!Iinclude/media/v4l2-mem2mem.h
265!Iinclude/media/v4l2-of.h
266!Iinclude/media/v4l2-rect.h
267!Iinclude/media/v4l2-subdev.h
268!Iinclude/media/videobuf2-core.h
269!Iinclude/media/videobuf2-v4l2.h
270!Iinclude/media/videobuf2-memops.h
271 </sect1>
272 <sect1><title>Digital TV (DVB) devices</title>
273 <sect1><title>Digital TV Common functions</title>
274!Idrivers/media/dvb-core/dvb_math.h
275!Idrivers/media/dvb-core/dvb_ringbuffer.h
276!Idrivers/media/dvb-core/dvbdev.h
277 </sect1>
278 <sect1><title>Digital TV Frontend kABI</title>
279!Pdrivers/media/dvb-core/dvb_frontend.h Digital TV Frontend
280!Idrivers/media/dvb-core/dvb_frontend.h
281 </sect1>
282 <sect1><title>Digital TV Demux kABI</title>
283!Pdrivers/media/dvb-core/demux.h Digital TV Demux
284 <sect1><title>Demux Callback API</title>
285!Pdrivers/media/dvb-core/demux.h Demux Callback
286 </sect1>
287!Idrivers/media/dvb-core/demux.h
288 </sect1>
289 <sect1><title>Digital TV Conditional Access kABI</title>
290!Idrivers/media/dvb-core/dvb_ca_en50221.h
291 </sect1>
292 </sect1>
293 <sect1><title>Remote Controller devices</title>
294!Iinclude/media/rc-core.h
295!Iinclude/media/lirc_dev.h
296 </sect1>
297 <sect1><title>Media Controller devices</title>
298!Pinclude/media/media-device.h Media Controller
299!Iinclude/media/media-device.h
300!Iinclude/media/media-devnode.h
301!Iinclude/media/media-entity.h
302 </sect1>
303
304 </chapter>
305
306 <chapter id="uart16x50">
307 <title>16x50 UART Driver</title>
308!Edrivers/tty/serial/serial_core.c
309!Edrivers/tty/serial/8250/8250_core.c
310 </chapter>
311
312 <chapter id="fbdev">
313 <title>Frame Buffer Library</title>
314
315 <para>
316 The frame buffer drivers depend heavily on four data structures.
317 These structures are declared in include/linux/fb.h. They are
318 fb_info, fb_var_screeninfo, fb_fix_screeninfo and fb_monospecs.
319 The last three can be made available to and from userland.
320 </para>
321
322 <para>
323 fb_info defines the current state of a particular video card.
324 Inside fb_info, there exists a fb_ops structure which is a
325 collection of needed functions to make fbdev and fbcon work.
326 fb_info is only visible to the kernel.
327 </para>
328
329 <para>
330 fb_var_screeninfo is used to describe the features of a video card
331 that are user defined. With fb_var_screeninfo, things such as
332 depth and the resolution may be defined.
333 </para>
334
335 <para>
336 The next structure is fb_fix_screeninfo. This defines the
337 properties of a card that are created when a mode is set and can't
338 be changed otherwise. A good example of this is the start of the
339 frame buffer memory. This "locks" the address of the frame buffer
340 memory, so that it cannot be changed or moved.
341 </para>
342
343 <para>
344 The last structure is fb_monospecs. In the old API, there was
345 little importance for fb_monospecs. This allowed for forbidden things
346 such as setting a mode of 800x600 on a fix frequency monitor. With
347 the new API, fb_monospecs prevents such things, and if used
348 correctly, can prevent a monitor from being cooked. fb_monospecs
349 will not be useful until kernels 2.5.x.
350 </para>
351
352 <sect1><title>Frame Buffer Memory</title>
353!Edrivers/video/fbdev/core/fbmem.c
354 </sect1>
355<!--
356 <sect1><title>Frame Buffer Console</title>
357X!Edrivers/video/console/fbcon.c
358 </sect1>
359-->
360 <sect1><title>Frame Buffer Colormap</title>
361!Edrivers/video/fbdev/core/fbcmap.c
362 </sect1>
363<!-- FIXME:
364 drivers/video/fbgen.c has no docs, which stuffs up the sgml. Comment
365 out until somebody adds docs. KAO
366 <sect1><title>Frame Buffer Generic Functions</title>
367X!Idrivers/video/fbgen.c
368 </sect1>
369KAO -->
370 <sect1><title>Frame Buffer Video Mode Database</title>
371!Idrivers/video/fbdev/core/modedb.c
372!Edrivers/video/fbdev/core/modedb.c
373 </sect1>
374 <sect1><title>Frame Buffer Macintosh Video Mode Database</title>
375!Edrivers/video/fbdev/macmodes.c
376 </sect1>
377 <sect1><title>Frame Buffer Fonts</title>
378 <para>
379 Refer to the file lib/fonts/fonts.c for more information.
380 </para>
381<!-- FIXME: Removed for now since no structured comments in source
382X!Ilib/fonts/fonts.c
383-->
384 </sect1>
385 </chapter>
386
387 <chapter id="input_subsystem">
388 <title>Input Subsystem</title>
389 <sect1><title>Input core</title>
390!Iinclude/linux/input.h
391!Edrivers/input/input.c
392!Edrivers/input/ff-core.c
393!Edrivers/input/ff-memless.c
394 </sect1>
395 <sect1><title>Multitouch Library</title>
396!Iinclude/linux/input/mt.h
397!Edrivers/input/input-mt.c
398 </sect1>
399 <sect1><title>Polled input devices</title>
400!Iinclude/linux/input-polldev.h
401!Edrivers/input/input-polldev.c
402 </sect1>
403 <sect1><title>Matrix keyboards/keypads</title>
404!Iinclude/linux/input/matrix_keypad.h
405 </sect1>
406 <sect1><title>Sparse keymap support</title>
407!Iinclude/linux/input/sparse-keymap.h
408!Edrivers/input/sparse-keymap.c
409 </sect1>
410 </chapter>
411
412 <chapter id="spi">
413 <title>Serial Peripheral Interface (SPI)</title>
414 <para>
415 SPI is the "Serial Peripheral Interface", widely used with
416 embedded systems because it is a simple and efficient
417 interface: basically a multiplexed shift register.
418 Its three signal wires hold a clock (SCK, often in the range
419 of 1-20 MHz), a "Master Out, Slave In" (MOSI) data line, and
420 a "Master In, Slave Out" (MISO) data line.
421 SPI is a full duplex protocol; for each bit shifted out the
422 MOSI line (one per clock) another is shifted in on the MISO line.
423 Those bits are assembled into words of various sizes on the
424 way to and from system memory.
425 An additional chipselect line is usually active-low (nCS);
426 four signals are normally used for each peripheral, plus
427 sometimes an interrupt.
428 </para>
429 <para>
430 The SPI bus facilities listed here provide a generalized
431 interface to declare SPI busses and devices, manage them
432 according to the standard Linux driver model, and perform
433 input/output operations.
434 At this time, only "master" side interfaces are supported,
435 where Linux talks to SPI peripherals and does not implement
436 such a peripheral itself.
437 (Interfaces to support implementing SPI slaves would
438 necessarily look different.)
439 </para>
440 <para>
441 The programming interface is structured around two kinds of driver,
442 and two kinds of device.
443 A "Controller Driver" abstracts the controller hardware, which may
444 be as simple as a set of GPIO pins or as complex as a pair of FIFOs
445 connected to dual DMA engines on the other side of the SPI shift
446 register (maximizing throughput). Such drivers bridge between
447 whatever bus they sit on (often the platform bus) and SPI, and
448 expose the SPI side of their device as a
449 <structname>struct spi_master</structname>.
450 SPI devices are children of that master, represented as a
451 <structname>struct spi_device</structname> and manufactured from
452 <structname>struct spi_board_info</structname> descriptors which
453 are usually provided by board-specific initialization code.
454 A <structname>struct spi_driver</structname> is called a
455 "Protocol Driver", and is bound to a spi_device using normal
456 driver model calls.
457 </para>
458 <para>
459 The I/O model is a set of queued messages. Protocol drivers
460 submit one or more <structname>struct spi_message</structname>
461 objects, which are processed and completed asynchronously.
462 (There are synchronous wrappers, however.) Messages are
463 built from one or more <structname>struct spi_transfer</structname>
464 objects, each of which wraps a full duplex SPI transfer.
465 A variety of protocol tweaking options are needed, because
466 different chips adopt very different policies for how they
467 use the bits transferred with SPI.
468 </para>
469!Iinclude/linux/spi/spi.h
470!Fdrivers/spi/spi.c spi_register_board_info
471!Edrivers/spi/spi.c
472 </chapter>
473
474 <chapter id="i2c">
475 <title>I<superscript>2</superscript>C and SMBus Subsystem</title>
476
477 <para>
478 I<superscript>2</superscript>C (or without fancy typography, "I2C")
479 is an acronym for the "Inter-IC" bus, a simple bus protocol which is
480 widely used where low data rate communications suffice.
481 Since it's also a licensed trademark, some vendors use another
482 name (such as "Two-Wire Interface", TWI) for the same bus.
483 I2C only needs two signals (SCL for clock, SDA for data), conserving
484 board real estate and minimizing signal quality issues.
485 Most I2C devices use seven bit addresses, and bus speeds of up
486 to 400 kHz; there's a high speed extension (3.4 MHz) that's not yet
487 found wide use.
488 I2C is a multi-master bus; open drain signaling is used to
489 arbitrate between masters, as well as to handshake and to
490 synchronize clocks from slower clients.
491 </para>
492
493 <para>
494 The Linux I2C programming interfaces support only the master
495 side of bus interactions, not the slave side.
496 The programming interface is structured around two kinds of driver,
497 and two kinds of device.
498 An I2C "Adapter Driver" abstracts the controller hardware; it binds
499 to a physical device (perhaps a PCI device or platform_device) and
500 exposes a <structname>struct i2c_adapter</structname> representing
501 each I2C bus segment it manages.
502 On each I2C bus segment will be I2C devices represented by a
503 <structname>struct i2c_client</structname>. Those devices will
504 be bound to a <structname>struct i2c_driver</structname>,
505 which should follow the standard Linux driver model.
506 (At this writing, a legacy model is more widely used.)
507 There are functions to perform various I2C protocol operations; at
508 this writing all such functions are usable only from task context.
509 </para>
510
511 <para>
512 The System Management Bus (SMBus) is a sibling protocol. Most SMBus
513 systems are also I2C conformant. The electrical constraints are
514 tighter for SMBus, and it standardizes particular protocol messages
515 and idioms. Controllers that support I2C can also support most
516 SMBus operations, but SMBus controllers don't support all the protocol
517 options that an I2C controller will.
518 There are functions to perform various SMBus protocol operations,
519 either using I2C primitives or by issuing SMBus commands to
520 i2c_adapter devices which don't support those I2C operations.
521 </para>
522
523!Iinclude/linux/i2c.h
524!Fdrivers/i2c/i2c-boardinfo.c i2c_register_board_info
525!Edrivers/i2c/i2c-core.c
526 </chapter>
527
528 <chapter id="hsi">
529 <title>High Speed Synchronous Serial Interface (HSI)</title>
530
531 <para>
532 High Speed Synchronous Serial Interface (HSI) is a
533 serial interface mainly used for connecting application
534 engines (APE) with cellular modem engines (CMT) in cellular
535 handsets.
536
537 HSI provides multiplexing for up to 16 logical channels,
538 low-latency and full duplex communication.
539 </para>
540
541!Iinclude/linux/hsi/hsi.h
542!Edrivers/hsi/hsi.c
543 </chapter>
544
545 <chapter id="pwm">
546 <title>Pulse-Width Modulation (PWM)</title>
547 <para>
548 Pulse-width modulation is a modulation technique primarily used to
549 control power supplied to electrical devices.
550 </para>
551 <para>
552 The PWM framework provides an abstraction for providers and consumers
553 of PWM signals. A controller that provides one or more PWM signals is
554 registered as <structname>struct pwm_chip</structname>. Providers are
555 expected to embed this structure in a driver-specific structure. This
556 structure contains fields that describe a particular chip.
557 </para>
558 <para>
559 A chip exposes one or more PWM signal sources, each of which exposed
560 as a <structname>struct pwm_device</structname>. Operations can be
561 performed on PWM devices to control the period, duty cycle, polarity
562 and active state of the signal.
563 </para>
564 <para>
565 Note that PWM devices are exclusive resources: they can always only be
566 used by one consumer at a time.
567 </para>
568!Iinclude/linux/pwm.h
569!Edrivers/pwm/core.c
570 </chapter>
571
572</book>