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" []>
5 <book id="LinuxKernelAPI">
7 <title>The Linux Kernel API</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 !Iinclude/asm-x86/atomic_32.h
49 !Iinclude/asm-x86/unaligned.h
52 <sect1><title>Delaying, scheduling, and timer routines</title>
53 !Iinclude/linux/sched.h
57 <sect1><title>High-resolution timers</title>
58 !Iinclude/linux/ktime.h
59 !Iinclude/linux/hrtimer.h
62 <sect1><title>Workqueues and Kevents</title>
65 <sect1><title>Internal Functions</title>
68 !Iinclude/linux/kthread.h
72 <sect1><title>Kernel objects manipulation</title>
74 X!Iinclude/linux/kobject.h
79 <sect1><title>Kernel utility functions</title>
80 !Iinclude/linux/kernel.h
87 <sect1><title>Device Resource Management</title>
88 !Edrivers/base/devres.c
94 <title>Data Types</title>
95 <sect1><title>Doubly Linked Lists</title>
96 !Iinclude/linux/list.h
101 <title>Basic C Library Functions</title>
104 When writing drivers, you cannot in general use routines which are
105 from the C Library. Some of the functions have been found generally
106 useful and they are listed below. The behaviour of these functions
107 may vary slightly from those defined by ANSI, and these deviations
108 are noted in the text.
111 <sect1><title>String Conversions</title>
115 <sect1><title>String Manipulation</title>
116 <!-- All functions are exported at now
121 <sect1><title>Bit Operations</title>
122 !Iinclude/asm-x86/bitops_32.h
126 <chapter id="kernel-lib">
127 <title>Basic Kernel Library Functions</title>
130 The Linux kernel provides more basic utility functions.
133 <sect1><title>Bitmap Operations</title>
138 <sect1><title>Command-line Parsing</title>
142 <sect1 id="crc"><title>CRC Functions</title>
152 <title>Memory Management in Linux</title>
153 <sect1><title>The Slab Cache</title>
154 !Iinclude/linux/slab.h
157 <sect1><title>User Space Memory Access</title>
158 !Iinclude/asm-x86/uaccess_32.h
159 !Earch/x86/lib/usercopy_32.c
161 <sect1><title>More Memory Management Functions</title>
169 !Emm/page-writeback.c
176 <title>Kernel IPC facilities</title>
178 <sect1><title>IPC utilities</title>
184 <title>FIFO Buffer</title>
185 <sect1><title>kfifo interface</title>
186 !Iinclude/linux/kfifo.h
191 <chapter id="relayfs">
192 <title>relay interface support</title>
195 Relay interface support
196 is designed to provide an efficient mechanism for tools and
197 facilities to relay large amounts of data from kernel space to
201 <sect1><title>relay interface</title>
207 <chapter id="modload">
208 <title>Module Support</title>
209 <sect1><title>Module Loading</title>
212 <sect1><title>Inter Module support</title>
214 Refer to the file kernel/module.c for more information.
216 <!-- FIXME: Removed for now since no structured comments in source
222 <chapter id="hardware">
223 <title>Hardware Interfaces</title>
224 <sect1><title>Interrupt Handling</title>
225 !Ekernel/irq/manage.c
228 <sect1><title>DMA Channels</title>
232 <sect1><title>Resources Management</title>
237 <sect1><title>MTRR Handling</title>
238 !Earch/x86/kernel/cpu/mtrr/main.c
241 <sect1><title>PCI Support Library</title>
243 !Edrivers/pci/pci-driver.c
244 !Edrivers/pci/remove.c
245 !Edrivers/pci/pci-acpi.c
246 !Edrivers/pci/search.c
249 <!-- FIXME: Removed for now since no structured comments in source
250 X!Edrivers/pci/hotplug.c
252 !Edrivers/pci/probe.c
255 <sect1><title>PCI Hotplug Support Library</title>
256 !Edrivers/pci/hotplug/pci_hotplug_core.c
258 <sect1><title>MCA Architecture</title>
259 <sect2><title>MCA Device Functions</title>
261 Refer to the file arch/x86/kernel/mca_32.c for more information.
263 <!-- FIXME: Removed for now since no structured comments in source
264 X!Earch/x86/kernel/mca_32.c
267 <sect2><title>MCA Bus DMA</title>
268 !Iinclude/asm-x86/mca_dma.h
273 <chapter id="firmware">
274 <title>Firmware Interfaces</title>
275 <sect1><title>DMI Interfaces</title>
276 !Edrivers/firmware/dmi_scan.c
278 <sect1><title>EDD Interfaces</title>
279 !Idrivers/firmware/edd.c
283 <chapter id="security">
284 <title>Security Framework</title>
285 !Isecurity/security.c
289 <title>Audit Interfaces</title>
292 !Ikernel/auditfilter.c
295 <chapter id="accounting">
296 <title>Accounting Framework</title>
300 <chapter id="pmfuncs">
301 <title>Power Management</title>
305 <chapter id="devdrivers">
306 <title>Device drivers infrastructure</title>
307 <sect1><title>Device Drivers Base</title>
309 X!Iinclude/linux/device.h
311 !Edrivers/base/driver.c
312 !Edrivers/base/core.c
313 !Edrivers/base/class.c
314 !Edrivers/base/firmware_class.c
315 !Edrivers/base/transport_class.c
316 <!-- Cannot be included, because
317 attribute_container_add_class_device_adapter
318 and attribute_container_classdev_to_container
319 exceed allowed 44 characters maximum
320 X!Edrivers/base/attribute_container.c
324 X!Edrivers/base/interface.c
326 !Edrivers/base/platform.c
329 <sect1><title>Device Drivers Power Management</title>
330 !Edrivers/base/power/main.c
332 <sect1><title>Device Drivers ACPI Support</title>
333 <!-- Internal functions only
334 X!Edrivers/acpi/sleep/main.c
335 X!Edrivers/acpi/sleep/wakeup.c
336 X!Edrivers/acpi/motherboard.c
337 X!Edrivers/acpi/bus.c
339 !Edrivers/acpi/scan.c
340 !Idrivers/acpi/scan.c
341 <!-- No correct structured comments
342 X!Edrivers/acpi/pci_bind.c
345 <sect1><title>Device drivers PnP support</title>
347 <!-- No correct structured comments
348 X!Edrivers/pnp/system.c
351 !Idrivers/pnp/driver.c
352 !Edrivers/pnp/manager.c
353 !Edrivers/pnp/support.c
355 <sect1><title>Userspace IO devices</title>
357 !Iinclude/linux/uio_driver.h
361 <chapter id="blkdev">
362 <title>Block Devices</title>
366 !Eblock/blk-settings.c
368 !Eblock/blk-barrier.c
372 <chapter id="chrdev">
373 <title>Char devices</title>
377 <chapter id="miscdev">
378 <title>Miscellaneous Devices</title>
379 !Edrivers/char/misc.c
382 <chapter id="parportdev">
383 <title>Parallel Port Devices</title>
384 !Iinclude/linux/parport.h
385 !Edrivers/parport/ieee1284.c
386 !Edrivers/parport/share.c
387 !Idrivers/parport/daisy.c
390 <chapter id="message_devices">
391 <title>Message-based devices</title>
392 <sect1><title>Fusion message devices</title>
393 !Edrivers/message/fusion/mptbase.c
394 !Idrivers/message/fusion/mptbase.c
395 !Edrivers/message/fusion/mptscsih.c
396 !Idrivers/message/fusion/mptscsih.c
397 !Idrivers/message/fusion/mptctl.c
398 !Idrivers/message/fusion/mptspi.c
399 !Idrivers/message/fusion/mptfc.c
400 !Idrivers/message/fusion/mptlan.c
402 <sect1><title>I2O message devices</title>
403 !Iinclude/linux/i2o.h
404 !Idrivers/message/i2o/core.h
405 !Edrivers/message/i2o/iop.c
406 !Idrivers/message/i2o/iop.c
407 !Idrivers/message/i2o/config-osm.c
408 !Edrivers/message/i2o/exec-osm.c
409 !Idrivers/message/i2o/exec-osm.c
410 !Idrivers/message/i2o/bus-osm.c
411 !Edrivers/message/i2o/device.c
412 !Idrivers/message/i2o/device.c
413 !Idrivers/message/i2o/driver.c
414 !Idrivers/message/i2o/pci.c
415 !Idrivers/message/i2o/i2o_block.c
416 !Idrivers/message/i2o/i2o_scsi.c
417 !Idrivers/message/i2o/i2o_proc.c
421 <chapter id="snddev">
422 <title>Sound Devices</title>
423 !Iinclude/sound/core.h
425 !Iinclude/sound/pcm.h
427 !Esound/core/device.c
429 !Esound/core/rawmidi.c
431 !Esound/core/memory.c
432 !Esound/core/pcm_memory.c
434 !Esound/core/isadma.c
435 !Esound/core/control.c
436 !Esound/core/pcm_lib.c
438 !Esound/core/pcm_native.c
439 !Esound/core/memalloc.c
440 <!-- FIXME: Removed for now since no structured comments in source
441 X!Isound/sound_firmware.c
445 <chapter id="uart16x50">
446 <title>16x50 UART Driver</title>
447 !Iinclude/linux/serial_core.h
448 !Edrivers/serial/serial_core.c
449 !Edrivers/serial/8250.c
452 <chapter id="z85230">
453 <title>Z85230 Support Library</title>
454 !Edrivers/net/wan/z85230.c
458 <title>Frame Buffer Library</title>
461 The frame buffer drivers depend heavily on four data structures.
462 These structures are declared in include/linux/fb.h. They are
463 fb_info, fb_var_screeninfo, fb_fix_screeninfo and fb_monospecs.
464 The last three can be made available to and from userland.
468 fb_info defines the current state of a particular video card.
469 Inside fb_info, there exists a fb_ops structure which is a
470 collection of needed functions to make fbdev and fbcon work.
471 fb_info is only visible to the kernel.
475 fb_var_screeninfo is used to describe the features of a video card
476 that are user defined. With fb_var_screeninfo, things such as
477 depth and the resolution may be defined.
481 The next structure is fb_fix_screeninfo. This defines the
482 properties of a card that are created when a mode is set and can't
483 be changed otherwise. A good example of this is the start of the
484 frame buffer memory. This "locks" the address of the frame buffer
485 memory, so that it cannot be changed or moved.
489 The last structure is fb_monospecs. In the old API, there was
490 little importance for fb_monospecs. This allowed for forbidden things
491 such as setting a mode of 800x600 on a fix frequency monitor. With
492 the new API, fb_monospecs prevents such things, and if used
493 correctly, can prevent a monitor from being cooked. fb_monospecs
494 will not be useful until kernels 2.5.x.
497 <sect1><title>Frame Buffer Memory</title>
498 !Edrivers/video/fbmem.c
501 <sect1><title>Frame Buffer Console</title>
502 X!Edrivers/video/console/fbcon.c
505 <sect1><title>Frame Buffer Colormap</title>
506 !Edrivers/video/fbcmap.c
509 drivers/video/fbgen.c has no docs, which stuffs up the sgml. Comment
510 out until somebody adds docs. KAO
511 <sect1><title>Frame Buffer Generic Functions</title>
512 X!Idrivers/video/fbgen.c
515 <sect1><title>Frame Buffer Video Mode Database</title>
516 !Idrivers/video/modedb.c
517 !Edrivers/video/modedb.c
519 <sect1><title>Frame Buffer Macintosh Video Mode Database</title>
520 !Edrivers/video/macmodes.c
522 <sect1><title>Frame Buffer Fonts</title>
524 Refer to the file drivers/video/console/fonts.c for more information.
526 <!-- FIXME: Removed for now since no structured comments in source
527 X!Idrivers/video/console/fonts.c
532 <chapter id="input_subsystem">
533 <title>Input Subsystem</title>
534 !Iinclude/linux/input.h
535 !Edrivers/input/input.c
536 !Edrivers/input/ff-core.c
537 !Edrivers/input/ff-memless.c
541 <title>Serial Peripheral Interface (SPI)</title>
543 SPI is the "Serial Peripheral Interface", widely used with
544 embedded systems because it is a simple and efficient
545 interface: basically a multiplexed shift register.
546 Its three signal wires hold a clock (SCK, often in the range
547 of 1-20 MHz), a "Master Out, Slave In" (MOSI) data line, and
548 a "Master In, Slave Out" (MISO) data line.
549 SPI is a full duplex protocol; for each bit shifted out the
550 MOSI line (one per clock) another is shifted in on the MISO line.
551 Those bits are assembled into words of various sizes on the
552 way to and from system memory.
553 An additional chipselect line is usually active-low (nCS);
554 four signals are normally used for each peripheral, plus
555 sometimes an interrupt.
558 The SPI bus facilities listed here provide a generalized
559 interface to declare SPI busses and devices, manage them
560 according to the standard Linux driver model, and perform
561 input/output operations.
562 At this time, only "master" side interfaces are supported,
563 where Linux talks to SPI peripherals and does not implement
564 such a peripheral itself.
565 (Interfaces to support implementing SPI slaves would
566 necessarily look different.)
569 The programming interface is structured around two kinds of driver,
570 and two kinds of device.
571 A "Controller Driver" abstracts the controller hardware, which may
572 be as simple as a set of GPIO pins or as complex as a pair of FIFOs
573 connected to dual DMA engines on the other side of the SPI shift
574 register (maximizing throughput). Such drivers bridge between
575 whatever bus they sit on (often the platform bus) and SPI, and
576 expose the SPI side of their device as a
577 <structname>struct spi_master</structname>.
578 SPI devices are children of that master, represented as a
579 <structname>struct spi_device</structname> and manufactured from
580 <structname>struct spi_board_info</structname> descriptors which
581 are usually provided by board-specific initialization code.
582 A <structname>struct spi_driver</structname> is called a
583 "Protocol Driver", and is bound to a spi_device using normal
587 The I/O model is a set of queued messages. Protocol drivers
588 submit one or more <structname>struct spi_message</structname>
589 objects, which are processed and completed asynchronously.
590 (There are synchronous wrappers, however.) Messages are
591 built from one or more <structname>struct spi_transfer</structname>
592 objects, each of which wraps a full duplex SPI transfer.
593 A variety of protocol tweaking options are needed, because
594 different chips adopt very different policies for how they
595 use the bits transferred with SPI.
597 !Iinclude/linux/spi/spi.h
598 !Fdrivers/spi/spi.c spi_register_board_info
603 <title>I<superscript>2</superscript>C and SMBus Subsystem</title>
606 I<superscript>2</superscript>C (or without fancy typography, "I2C")
607 is an acronym for the "Inter-IC" bus, a simple bus protocol which is
608 widely used where low data rate communications suffice.
609 Since it's also a licensed trademark, some vendors use another
610 name (such as "Two-Wire Interface", TWI) for the same bus.
611 I2C only needs two signals (SCL for clock, SDA for data), conserving
612 board real estate and minimizing signal quality issues.
613 Most I2C devices use seven bit addresses, and bus speeds of up
614 to 400 kHz; there's a high speed extension (3.4 MHz) that's not yet
616 I2C is a multi-master bus; open drain signaling is used to
617 arbitrate between masters, as well as to handshake and to
618 synchronize clocks from slower clients.
622 The Linux I2C programming interfaces support only the master
623 side of bus interactions, not the slave side.
624 The programming interface is structured around two kinds of driver,
625 and two kinds of device.
626 An I2C "Adapter Driver" abstracts the controller hardware; it binds
627 to a physical device (perhaps a PCI device or platform_device) and
628 exposes a <structname>struct i2c_adapter</structname> representing
629 each I2C bus segment it manages.
630 On each I2C bus segment will be I2C devices represented by a
631 <structname>struct i2c_client</structname>. Those devices will
632 be bound to a <structname>struct i2c_driver</structname>,
633 which should follow the standard Linux driver model.
634 (At this writing, a legacy model is more widely used.)
635 There are functions to perform various I2C protocol operations; at
636 this writing all such functions are usable only from task context.
640 The System Management Bus (SMBus) is a sibling protocol. Most SMBus
641 systems are also I2C conformant. The electrical constraints are
642 tighter for SMBus, and it standardizes particular protocol messages
643 and idioms. Controllers that support I2C can also support most
644 SMBus operations, but SMBus controllers don't support all the protocol
645 options that an I2C controller will.
646 There are functions to perform various SMBus protocol operations,
647 either using I2C primitives or by issuing SMBus commands to
648 i2c_adapter devices which don't support those I2C operations.
651 !Iinclude/linux/i2c.h
652 !Fdrivers/i2c/i2c-boardinfo.c i2c_register_board_info
653 !Edrivers/i2c/i2c-core.c