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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><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
147X!Edrivers/acpi/sleep/main.c
148X!Edrivers/acpi/sleep/wakeup.c
149X!Edrivers/acpi/motherboard.c
150X!Edrivers/acpi/bus.c
151-->
152!Edrivers/acpi/scan.c
153!Idrivers/acpi/scan.c
154<!-- No correct structured comments
155X!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
161X!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
216X!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>
325X!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>
335X!Idrivers/video/fbgen.c
336 </sect1>
337KAO -->
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
350X!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>