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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 !Ikernel/sched/cpupri.c
56 !Iinclude/linux/completion.h
59 <sect1><title>Wait queues and Wake events</title>
60 !Iinclude/linux/wait.h
63 <sect1><title>High-resolution timers</title>
64 !Iinclude/linux/ktime.h
65 !Iinclude/linux/hrtimer.h
66 !Ekernel/time/hrtimer.c
68 <sect1><title>Workqueues and Kevents</title>
69 !Iinclude/linux/workqueue.h
72 <sect1><title>Internal Functions</title>
75 !Iinclude/linux/kthread.h
79 <sect1><title>Kernel objects manipulation</title>
81 X!Iinclude/linux/kobject.h
86 <sect1><title>Kernel utility functions</title>
87 !Iinclude/linux/kernel.h
88 !Ekernel/printk/printk.c
93 !Ekernel/rcu/tree_plugin.h
97 <sect1><title>Device Resource Management</title>
98 !Edrivers/base/devres.c
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
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
125 X!Edrivers/base/interface.c
127 !Iinclude/linux/platform_device.h
128 !Edrivers/base/platform.c
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
142 <sect1><title>Device Drivers Power Management</title>
143 !Edrivers/base/power/main.c
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
152 !Edrivers/acpi/scan.c
153 !Idrivers/acpi/scan.c
154 <!-- No correct structured comments
155 X!Edrivers/acpi/pci_bind.c
158 <sect1><title>Device drivers PnP support</title>
160 <!-- No correct structured comments
161 X!Edrivers/pnp/system.c
164 !Idrivers/pnp/driver.c
165 !Edrivers/pnp/manager.c
166 !Edrivers/pnp/support.c
168 <sect1><title>Userspace IO devices</title>
170 !Iinclude/linux/uio_driver.h
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
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
196 <chapter id="snddev">
197 <title>Sound Devices</title>
198 !Iinclude/sound/core.h
200 !Iinclude/sound/pcm.h
202 !Esound/core/device.c
204 !Esound/core/rawmidi.c
206 !Esound/core/memory.c
207 !Esound/core/pcm_memory.c
209 !Esound/core/isadma.c
210 !Esound/core/control.c
211 !Esound/core/pcm_lib.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
220 <chapter id="uart16x50">
221 <title>16x50 UART Driver</title>
222 !Edrivers/tty/serial/serial_core.c
223 !Edrivers/tty/serial/8250/8250_core.c
227 <title>Frame Buffer Library</title>
230 The frame buffer drivers depend heavily on four data structures.
231 These structures are declared in include/linux/fb.h. They are
232 fb_info, fb_var_screeninfo, fb_fix_screeninfo and fb_monospecs.
233 The last three can be made available to and from userland.
237 fb_info defines the current state of a particular video card.
238 Inside fb_info, there exists a fb_ops structure which is a
239 collection of needed functions to make fbdev and fbcon work.
240 fb_info is only visible to the kernel.
244 fb_var_screeninfo is used to describe the features of a video card
245 that are user defined. With fb_var_screeninfo, things such as
246 depth and the resolution may be defined.
250 The next structure is fb_fix_screeninfo. This defines the
251 properties of a card that are created when a mode is set and can't
252 be changed otherwise. A good example of this is the start of the
253 frame buffer memory. This "locks" the address of the frame buffer
254 memory, so that it cannot be changed or moved.
258 The last structure is fb_monospecs. In the old API, there was
259 little importance for fb_monospecs. This allowed for forbidden things
260 such as setting a mode of 800x600 on a fix frequency monitor. With
261 the new API, fb_monospecs prevents such things, and if used
262 correctly, can prevent a monitor from being cooked. fb_monospecs
263 will not be useful until kernels 2.5.x.
266 <sect1><title>Frame Buffer Memory</title>
267 !Edrivers/video/fbdev/core/fbmem.c
270 <sect1><title>Frame Buffer Console</title>
271 X!Edrivers/video/console/fbcon.c
274 <sect1><title>Frame Buffer Colormap</title>
275 !Edrivers/video/fbdev/core/fbcmap.c
278 drivers/video/fbgen.c has no docs, which stuffs up the sgml. Comment
279 out until somebody adds docs. KAO
280 <sect1><title>Frame Buffer Generic Functions</title>
281 X!Idrivers/video/fbgen.c
284 <sect1><title>Frame Buffer Video Mode Database</title>
285 !Idrivers/video/fbdev/core/modedb.c
286 !Edrivers/video/fbdev/core/modedb.c
288 <sect1><title>Frame Buffer Macintosh Video Mode Database</title>
289 !Edrivers/video/fbdev/macmodes.c
291 <sect1><title>Frame Buffer Fonts</title>
293 Refer to the file lib/fonts/fonts.c for more information.
295 <!-- FIXME: Removed for now since no structured comments in source
301 <chapter id="input_subsystem">
302 <title>Input Subsystem</title>
303 <sect1><title>Input core</title>
304 !Iinclude/linux/input.h
305 !Edrivers/input/input.c
306 !Edrivers/input/ff-core.c
307 !Edrivers/input/ff-memless.c
309 <sect1><title>Multitouch Library</title>
310 !Iinclude/linux/input/mt.h
311 !Edrivers/input/input-mt.c
313 <sect1><title>Polled input devices</title>
314 !Iinclude/linux/input-polldev.h
315 !Edrivers/input/input-polldev.c
317 <sect1><title>Matrix keyboars/keypads</title>
318 !Iinclude/linux/input/matrix_keypad.h
320 <sect1><title>Sparse keymap support</title>
321 !Iinclude/linux/input/sparse-keymap.h
322 !Edrivers/input/sparse-keymap.c
327 <title>Serial Peripheral Interface (SPI)</title>
329 SPI is the "Serial Peripheral Interface", widely used with
330 embedded systems because it is a simple and efficient
331 interface: basically a multiplexed shift register.
332 Its three signal wires hold a clock (SCK, often in the range
333 of 1-20 MHz), a "Master Out, Slave In" (MOSI) data line, and
334 a "Master In, Slave Out" (MISO) data line.
335 SPI is a full duplex protocol; for each bit shifted out the
336 MOSI line (one per clock) another is shifted in on the MISO line.
337 Those bits are assembled into words of various sizes on the
338 way to and from system memory.
339 An additional chipselect line is usually active-low (nCS);
340 four signals are normally used for each peripheral, plus
341 sometimes an interrupt.
344 The SPI bus facilities listed here provide a generalized
345 interface to declare SPI busses and devices, manage them
346 according to the standard Linux driver model, and perform
347 input/output operations.
348 At this time, only "master" side interfaces are supported,
349 where Linux talks to SPI peripherals and does not implement
350 such a peripheral itself.
351 (Interfaces to support implementing SPI slaves would
352 necessarily look different.)
355 The programming interface is structured around two kinds of driver,
356 and two kinds of device.
357 A "Controller Driver" abstracts the controller hardware, which may
358 be as simple as a set of GPIO pins or as complex as a pair of FIFOs
359 connected to dual DMA engines on the other side of the SPI shift
360 register (maximizing throughput). Such drivers bridge between
361 whatever bus they sit on (often the platform bus) and SPI, and
362 expose the SPI side of their device as a
363 <structname>struct spi_master</structname>.
364 SPI devices are children of that master, represented as a
365 <structname>struct spi_device</structname> and manufactured from
366 <structname>struct spi_board_info</structname> descriptors which
367 are usually provided by board-specific initialization code.
368 A <structname>struct spi_driver</structname> is called a
369 "Protocol Driver", and is bound to a spi_device using normal
373 The I/O model is a set of queued messages. Protocol drivers
374 submit one or more <structname>struct spi_message</structname>
375 objects, which are processed and completed asynchronously.
376 (There are synchronous wrappers, however.) Messages are
377 built from one or more <structname>struct spi_transfer</structname>
378 objects, each of which wraps a full duplex SPI transfer.
379 A variety of protocol tweaking options are needed, because
380 different chips adopt very different policies for how they
381 use the bits transferred with SPI.
383 !Iinclude/linux/spi/spi.h
384 !Fdrivers/spi/spi.c spi_register_board_info
389 <title>I<superscript>2</superscript>C and SMBus Subsystem</title>
392 I<superscript>2</superscript>C (or without fancy typography, "I2C")
393 is an acronym for the "Inter-IC" bus, a simple bus protocol which is
394 widely used where low data rate communications suffice.
395 Since it's also a licensed trademark, some vendors use another
396 name (such as "Two-Wire Interface", TWI) for the same bus.
397 I2C only needs two signals (SCL for clock, SDA for data), conserving
398 board real estate and minimizing signal quality issues.
399 Most I2C devices use seven bit addresses, and bus speeds of up
400 to 400 kHz; there's a high speed extension (3.4 MHz) that's not yet
402 I2C is a multi-master bus; open drain signaling is used to
403 arbitrate between masters, as well as to handshake and to
404 synchronize clocks from slower clients.
408 The Linux I2C programming interfaces support only the master
409 side of bus interactions, not the slave side.
410 The programming interface is structured around two kinds of driver,
411 and two kinds of device.
412 An I2C "Adapter Driver" abstracts the controller hardware; it binds
413 to a physical device (perhaps a PCI device or platform_device) and
414 exposes a <structname>struct i2c_adapter</structname> representing
415 each I2C bus segment it manages.
416 On each I2C bus segment will be I2C devices represented by a
417 <structname>struct i2c_client</structname>. Those devices will
418 be bound to a <structname>struct i2c_driver</structname>,
419 which should follow the standard Linux driver model.
420 (At this writing, a legacy model is more widely used.)
421 There are functions to perform various I2C protocol operations; at
422 this writing all such functions are usable only from task context.
426 The System Management Bus (SMBus) is a sibling protocol. Most SMBus
427 systems are also I2C conformant. The electrical constraints are
428 tighter for SMBus, and it standardizes particular protocol messages
429 and idioms. Controllers that support I2C can also support most
430 SMBus operations, but SMBus controllers don't support all the protocol
431 options that an I2C controller will.
432 There are functions to perform various SMBus protocol operations,
433 either using I2C primitives or by issuing SMBus commands to
434 i2c_adapter devices which don't support those I2C operations.
437 !Iinclude/linux/i2c.h
438 !Fdrivers/i2c/i2c-boardinfo.c i2c_register_board_info
439 !Edrivers/i2c/i2c-core.c
443 <title>High Speed Synchronous Serial Interface (HSI)</title>
446 High Speed Synchronous Serial Interface (HSI) is a
447 serial interface mainly used for connecting application
448 engines (APE) with cellular modem engines (CMT) in cellular
451 HSI provides multiplexing for up to 16 logical channels,
452 low-latency and full duplex communication.
455 !Iinclude/linux/hsi/hsi.h