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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" []>
5 <book id="LinuxDriversAPI">
7 <title>Linux Device Drivers</title>
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
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.
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,
33 For more details see the file COPYING in the source
34 distribution of Linux.
42 <title>Driver Basics</title>
43 <sect1><title>Driver Entry and Exit points</title>
44 !Iinclude/linux/init.h
47 <sect1><title>Atomic and pointer manipulation</title>
48 !Iarch/x86/include/asm/atomic.h
51 <sect1><title>Delaying, scheduling, and timer routines</title>
52 !Iinclude/linux/sched.h
54 !Iinclude/linux/completion.h
57 <sect1><title>Wait queues and Wake events</title>
58 !Iinclude/linux/wait.h
61 <sect1><title>High-resolution timers</title>
62 !Iinclude/linux/ktime.h
63 !Iinclude/linux/hrtimer.h
66 <sect1><title>Workqueues and Kevents</title>
69 <sect1><title>Internal Functions</title>
72 !Iinclude/linux/kthread.h
76 <sect1><title>Kernel objects manipulation</title>
78 X!Iinclude/linux/kobject.h
83 <sect1><title>Kernel utility functions</title>
84 !Iinclude/linux/kernel.h
91 <sect1><title>Device Resource Management</title>
92 !Edrivers/base/devres.c
97 <chapter id="devdrivers">
98 <title>Device drivers infrastructure</title>
99 <sect1><title>The Basic Device Driver-Model Structures </title>
100 !Iinclude/linux/device.h
102 <sect1><title>Device Drivers Base</title>
103 !Edrivers/base/driver.c
104 !Edrivers/base/core.c
105 !Edrivers/base/class.c
106 !Edrivers/base/firmware_class.c
107 !Edrivers/base/transport_class.c
108 <!-- Cannot be included, because
109 attribute_container_add_class_device_adapter
110 and attribute_container_classdev_to_container
111 exceed allowed 44 characters maximum
112 X!Edrivers/base/attribute_container.c
116 X!Edrivers/base/interface.c
118 !Iinclude/linux/platform_device.h
119 !Edrivers/base/platform.c
122 <sect1><title>Device Drivers Power Management</title>
123 !Edrivers/base/power/main.c
125 <sect1><title>Device Drivers ACPI Support</title>
126 <!-- Internal functions only
127 X!Edrivers/acpi/sleep/main.c
128 X!Edrivers/acpi/sleep/wakeup.c
129 X!Edrivers/acpi/motherboard.c
130 X!Edrivers/acpi/bus.c
132 !Edrivers/acpi/scan.c
133 !Idrivers/acpi/scan.c
134 <!-- No correct structured comments
135 X!Edrivers/acpi/pci_bind.c
138 <sect1><title>Device drivers PnP support</title>
140 <!-- No correct structured comments
141 X!Edrivers/pnp/system.c
144 !Idrivers/pnp/driver.c
145 !Edrivers/pnp/manager.c
146 !Edrivers/pnp/support.c
148 <sect1><title>Userspace IO devices</title>
150 !Iinclude/linux/uio_driver.h
154 <chapter id="parportdev">
155 <title>Parallel Port Devices</title>
156 !Iinclude/linux/parport.h
157 !Edrivers/parport/ieee1284.c
158 !Edrivers/parport/share.c
159 !Idrivers/parport/daisy.c
162 <chapter id="message_devices">
163 <title>Message-based devices</title>
164 <sect1><title>Fusion message devices</title>
165 !Edrivers/message/fusion/mptbase.c
166 !Idrivers/message/fusion/mptbase.c
167 !Edrivers/message/fusion/mptscsih.c
168 !Idrivers/message/fusion/mptscsih.c
169 !Idrivers/message/fusion/mptctl.c
170 !Idrivers/message/fusion/mptspi.c
171 !Idrivers/message/fusion/mptfc.c
172 !Idrivers/message/fusion/mptlan.c
174 <sect1><title>I2O message devices</title>
175 !Iinclude/linux/i2o.h
176 !Idrivers/message/i2o/core.h
177 !Edrivers/message/i2o/iop.c
178 !Idrivers/message/i2o/iop.c
179 !Idrivers/message/i2o/config-osm.c
180 !Edrivers/message/i2o/exec-osm.c
181 !Idrivers/message/i2o/exec-osm.c
182 !Idrivers/message/i2o/bus-osm.c
183 !Edrivers/message/i2o/device.c
184 !Idrivers/message/i2o/device.c
185 !Idrivers/message/i2o/driver.c
186 !Idrivers/message/i2o/pci.c
187 !Idrivers/message/i2o/i2o_block.c
188 !Idrivers/message/i2o/i2o_scsi.c
189 !Idrivers/message/i2o/i2o_proc.c
193 <chapter id="snddev">
194 <title>Sound Devices</title>
195 !Iinclude/sound/core.h
197 !Iinclude/sound/pcm.h
199 !Esound/core/device.c
201 !Esound/core/rawmidi.c
203 !Esound/core/memory.c
204 !Esound/core/pcm_memory.c
206 !Esound/core/isadma.c
207 !Esound/core/control.c
208 !Esound/core/pcm_lib.c
210 !Esound/core/pcm_native.c
211 !Esound/core/memalloc.c
212 <!-- FIXME: Removed for now since no structured comments in source
213 X!Isound/sound_firmware.c
217 <chapter id="uart16x50">
218 <title>16x50 UART Driver</title>
219 !Edrivers/tty/serial/serial_core.c
220 !Edrivers/tty/serial/8250.c
224 <title>Frame Buffer Library</title>
227 The frame buffer drivers depend heavily on four data structures.
228 These structures are declared in include/linux/fb.h. They are
229 fb_info, fb_var_screeninfo, fb_fix_screeninfo and fb_monospecs.
230 The last three can be made available to and from userland.
234 fb_info defines the current state of a particular video card.
235 Inside fb_info, there exists a fb_ops structure which is a
236 collection of needed functions to make fbdev and fbcon work.
237 fb_info is only visible to the kernel.
241 fb_var_screeninfo is used to describe the features of a video card
242 that are user defined. With fb_var_screeninfo, things such as
243 depth and the resolution may be defined.
247 The next structure is fb_fix_screeninfo. This defines the
248 properties of a card that are created when a mode is set and can't
249 be changed otherwise. A good example of this is the start of the
250 frame buffer memory. This "locks" the address of the frame buffer
251 memory, so that it cannot be changed or moved.
255 The last structure is fb_monospecs. In the old API, there was
256 little importance for fb_monospecs. This allowed for forbidden things
257 such as setting a mode of 800x600 on a fix frequency monitor. With
258 the new API, fb_monospecs prevents such things, and if used
259 correctly, can prevent a monitor from being cooked. fb_monospecs
260 will not be useful until kernels 2.5.x.
263 <sect1><title>Frame Buffer Memory</title>
264 !Edrivers/video/fbmem.c
267 <sect1><title>Frame Buffer Console</title>
268 X!Edrivers/video/console/fbcon.c
271 <sect1><title>Frame Buffer Colormap</title>
272 !Edrivers/video/fbcmap.c
275 drivers/video/fbgen.c has no docs, which stuffs up the sgml. Comment
276 out until somebody adds docs. KAO
277 <sect1><title>Frame Buffer Generic Functions</title>
278 X!Idrivers/video/fbgen.c
281 <sect1><title>Frame Buffer Video Mode Database</title>
282 !Idrivers/video/modedb.c
283 !Edrivers/video/modedb.c
285 <sect1><title>Frame Buffer Macintosh Video Mode Database</title>
286 !Edrivers/video/macmodes.c
288 <sect1><title>Frame Buffer Fonts</title>
290 Refer to the file drivers/video/console/fonts.c for more information.
292 <!-- FIXME: Removed for now since no structured comments in source
293 X!Idrivers/video/console/fonts.c
298 <chapter id="input_subsystem">
299 <title>Input Subsystem</title>
300 <sect1><title>Input core</title>
301 !Iinclude/linux/input.h
302 !Edrivers/input/input.c
303 !Edrivers/input/ff-core.c
304 !Edrivers/input/ff-memless.c
306 <sect1><title>Multitouch Library</title>
307 !Iinclude/linux/input/mt.h
308 !Edrivers/input/input-mt.c
310 <sect1><title>Polled input devices</title>
311 !Iinclude/linux/input-polldev.h
312 !Edrivers/input/input-polldev.c
314 <sect1><title>Matrix keyboars/keypads</title>
315 !Iinclude/linux/input/matrix_keypad.h
317 <sect1><title>Sparse keymap support</title>
318 !Iinclude/linux/input/sparse-keymap.h
319 !Edrivers/input/sparse-keymap.c
324 <title>Serial Peripheral Interface (SPI)</title>
326 SPI is the "Serial Peripheral Interface", widely used with
327 embedded systems because it is a simple and efficient
328 interface: basically a multiplexed shift register.
329 Its three signal wires hold a clock (SCK, often in the range
330 of 1-20 MHz), a "Master Out, Slave In" (MOSI) data line, and
331 a "Master In, Slave Out" (MISO) data line.
332 SPI is a full duplex protocol; for each bit shifted out the
333 MOSI line (one per clock) another is shifted in on the MISO line.
334 Those bits are assembled into words of various sizes on the
335 way to and from system memory.
336 An additional chipselect line is usually active-low (nCS);
337 four signals are normally used for each peripheral, plus
338 sometimes an interrupt.
341 The SPI bus facilities listed here provide a generalized
342 interface to declare SPI busses and devices, manage them
343 according to the standard Linux driver model, and perform
344 input/output operations.
345 At this time, only "master" side interfaces are supported,
346 where Linux talks to SPI peripherals and does not implement
347 such a peripheral itself.
348 (Interfaces to support implementing SPI slaves would
349 necessarily look different.)
352 The programming interface is structured around two kinds of driver,
353 and two kinds of device.
354 A "Controller Driver" abstracts the controller hardware, which may
355 be as simple as a set of GPIO pins or as complex as a pair of FIFOs
356 connected to dual DMA engines on the other side of the SPI shift
357 register (maximizing throughput). Such drivers bridge between
358 whatever bus they sit on (often the platform bus) and SPI, and
359 expose the SPI side of their device as a
360 <structname>struct spi_master</structname>.
361 SPI devices are children of that master, represented as a
362 <structname>struct spi_device</structname> and manufactured from
363 <structname>struct spi_board_info</structname> descriptors which
364 are usually provided by board-specific initialization code.
365 A <structname>struct spi_driver</structname> is called a
366 "Protocol Driver", and is bound to a spi_device using normal
370 The I/O model is a set of queued messages. Protocol drivers
371 submit one or more <structname>struct spi_message</structname>
372 objects, which are processed and completed asynchronously.
373 (There are synchronous wrappers, however.) Messages are
374 built from one or more <structname>struct spi_transfer</structname>
375 objects, each of which wraps a full duplex SPI transfer.
376 A variety of protocol tweaking options are needed, because
377 different chips adopt very different policies for how they
378 use the bits transferred with SPI.
380 !Iinclude/linux/spi/spi.h
381 !Fdrivers/spi/spi.c spi_register_board_info
386 <title>I<superscript>2</superscript>C and SMBus Subsystem</title>
389 I<superscript>2</superscript>C (or without fancy typography, "I2C")
390 is an acronym for the "Inter-IC" bus, a simple bus protocol which is
391 widely used where low data rate communications suffice.
392 Since it's also a licensed trademark, some vendors use another
393 name (such as "Two-Wire Interface", TWI) for the same bus.
394 I2C only needs two signals (SCL for clock, SDA for data), conserving
395 board real estate and minimizing signal quality issues.
396 Most I2C devices use seven bit addresses, and bus speeds of up
397 to 400 kHz; there's a high speed extension (3.4 MHz) that's not yet
399 I2C is a multi-master bus; open drain signaling is used to
400 arbitrate between masters, as well as to handshake and to
401 synchronize clocks from slower clients.
405 The Linux I2C programming interfaces support only the master
406 side of bus interactions, not the slave side.
407 The programming interface is structured around two kinds of driver,
408 and two kinds of device.
409 An I2C "Adapter Driver" abstracts the controller hardware; it binds
410 to a physical device (perhaps a PCI device or platform_device) and
411 exposes a <structname>struct i2c_adapter</structname> representing
412 each I2C bus segment it manages.
413 On each I2C bus segment will be I2C devices represented by a
414 <structname>struct i2c_client</structname>. Those devices will
415 be bound to a <structname>struct i2c_driver</structname>,
416 which should follow the standard Linux driver model.
417 (At this writing, a legacy model is more widely used.)
418 There are functions to perform various I2C protocol operations; at
419 this writing all such functions are usable only from task context.
423 The System Management Bus (SMBus) is a sibling protocol. Most SMBus
424 systems are also I2C conformant. The electrical constraints are
425 tighter for SMBus, and it standardizes particular protocol messages
426 and idioms. Controllers that support I2C can also support most
427 SMBus operations, but SMBus controllers don't support all the protocol
428 options that an I2C controller will.
429 There are functions to perform various SMBus protocol operations,
430 either using I2C primitives or by issuing SMBus commands to
431 i2c_adapter devices which don't support those I2C operations.
434 !Iinclude/linux/i2c.h
435 !Fdrivers/i2c/i2c-boardinfo.c i2c_register_board_info
436 !Edrivers/i2c/i2c-core.c