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-i386/atomic.h
49 !Iinclude/asm-i386/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-i386/bitops.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-i386/uaccess.h
159 !Earch/i386/lib/usercopy.c
161 <sect1><title>More Memory Management Functions</title>
168 !Emm/page-writeback.c
175 <title>Kernel IPC facilities</title>
177 <sect1><title>IPC utilities</title>
183 <title>FIFO Buffer</title>
184 <sect1><title>kfifo interface</title>
185 !Iinclude/linux/kfifo.h
190 <chapter id="relayfs">
191 <title>relay interface support</title>
194 Relay interface support
195 is designed to provide an efficient mechanism for tools and
196 facilities to relay large amounts of data from kernel space to
200 <sect1><title>relay interface</title>
206 <chapter id="netcore">
207 <title>Linux Networking</title>
208 <sect1><title>Networking Base Types</title>
209 !Iinclude/linux/net.h
211 <sect1><title>Socket Buffer Functions</title>
212 !Iinclude/linux/skbuff.h
217 !Enet/core/datagram.c
220 <sect1><title>Socket Filter</title>
223 <sect1><title>Generic Network Statistics</title>
224 !Iinclude/linux/gen_stats.h
225 !Enet/core/gen_stats.c
226 !Enet/core/gen_estimator.c
228 <sect1><title>SUN RPC subsystem</title>
229 <!-- The !D functionality is not perfect, garbage has to be protected by comments
230 !Dnet/sunrpc/sunrpc_syms.c
233 !Enet/sunrpc/svcsock.c
238 <chapter id="netdev">
239 <title>Network device support</title>
240 <sect1><title>Driver Support</title>
243 !Enet/sched/sch_generic.c
244 !Iinclude/linux/etherdevice.h
245 !Iinclude/linux/netdevice.h
247 <sect1><title>PHY Support</title>
248 !Edrivers/net/phy/phy.c
249 !Idrivers/net/phy/phy.c
250 !Edrivers/net/phy/phy_device.c
251 !Idrivers/net/phy/phy_device.c
252 !Edrivers/net/phy/mdio_bus.c
253 !Idrivers/net/phy/mdio_bus.c
255 <!-- FIXME: Removed for now since no structured comments in source
256 <sect1><title>Wireless</title>
257 X!Enet/core/wireless.c
260 <sect1><title>Synchronous PPP</title>
261 !Edrivers/net/wan/syncppp.c
265 <chapter id="modload">
266 <title>Module Support</title>
267 <sect1><title>Module Loading</title>
270 <sect1><title>Inter Module support</title>
272 Refer to the file kernel/module.c for more information.
274 <!-- FIXME: Removed for now since no structured comments in source
280 <chapter id="hardware">
281 <title>Hardware Interfaces</title>
282 <sect1><title>Interrupt Handling</title>
283 !Ekernel/irq/manage.c
286 <sect1><title>DMA Channels</title>
290 <sect1><title>Resources Management</title>
295 <sect1><title>MTRR Handling</title>
296 !Earch/i386/kernel/cpu/mtrr/main.c
299 <sect1><title>PCI Support Library</title>
301 !Edrivers/pci/pci-driver.c
302 !Edrivers/pci/remove.c
303 !Edrivers/pci/pci-acpi.c
304 !Edrivers/pci/search.c
307 <!-- FIXME: Removed for now since no structured comments in source
308 X!Edrivers/pci/hotplug.c
310 !Edrivers/pci/probe.c
313 <sect1><title>PCI Hotplug Support Library</title>
314 !Edrivers/pci/hotplug/pci_hotplug_core.c
316 <sect1><title>MCA Architecture</title>
317 <sect2><title>MCA Device Functions</title>
319 Refer to the file arch/i386/kernel/mca.c for more information.
321 <!-- FIXME: Removed for now since no structured comments in source
322 X!Earch/i386/kernel/mca.c
325 <sect2><title>MCA Bus DMA</title>
326 !Iinclude/asm-i386/mca_dma.h
331 <chapter id="firmware">
332 <title>Firmware Interfaces</title>
333 <sect1><title>DMI Interfaces</title>
334 !Edrivers/firmware/dmi_scan.c
336 <sect1><title>EDD Interfaces</title>
337 !Idrivers/firmware/edd.c
341 <chapter id="security">
342 <title>Security Framework</title>
343 !Esecurity/security.c
347 <title>Audit Interfaces</title>
350 !Ikernel/auditfilter.c
353 <chapter id="accounting">
354 <title>Accounting Framework</title>
358 <chapter id="pmfuncs">
359 <title>Power Management</title>
363 <chapter id="devdrivers">
364 <title>Device drivers infrastructure</title>
365 <sect1><title>Device Drivers Base</title>
367 X!Iinclude/linux/device.h
369 !Edrivers/base/driver.c
370 !Edrivers/base/core.c
371 !Edrivers/base/class.c
372 !Edrivers/base/firmware_class.c
373 !Edrivers/base/transport_class.c
374 !Edrivers/base/dmapool.c
375 <!-- Cannot be included, because
376 attribute_container_add_class_device_adapter
377 and attribute_container_classdev_to_container
378 exceed allowed 44 characters maximum
379 X!Edrivers/base/attribute_container.c
383 X!Edrivers/base/interface.c
385 !Edrivers/base/platform.c
388 <sect1><title>Device Drivers Power Management</title>
389 !Edrivers/base/power/resume.c
390 !Edrivers/base/power/suspend.c
392 <sect1><title>Device Drivers ACPI Support</title>
393 <!-- Internal functions only
394 X!Edrivers/acpi/sleep/main.c
395 X!Edrivers/acpi/sleep/wakeup.c
396 X!Edrivers/acpi/motherboard.c
397 X!Edrivers/acpi/bus.c
399 !Edrivers/acpi/scan.c
400 !Idrivers/acpi/scan.c
401 <!-- No correct structured comments
402 X!Edrivers/acpi/pci_bind.c
405 <sect1><title>Device drivers PnP support</title>
407 <!-- No correct structured comments
408 X!Edrivers/pnp/system.c
411 !Idrivers/pnp/driver.c
412 !Edrivers/pnp/manager.c
413 !Edrivers/pnp/support.c
415 <sect1><title>Userspace IO devices</title>
417 !Iinclude/linux/uio_driver.h
421 <chapter id="blkdev">
422 <title>Block Devices</title>
426 <chapter id="chrdev">
427 <title>Char devices</title>
431 <chapter id="miscdev">
432 <title>Miscellaneous Devices</title>
433 !Edrivers/char/misc.c
436 <chapter id="parportdev">
437 <title>Parallel Port Devices</title>
438 !Iinclude/linux/parport.h
439 !Edrivers/parport/ieee1284.c
440 !Edrivers/parport/share.c
441 !Idrivers/parport/daisy.c
444 <chapter id="message_devices">
445 <title>Message-based devices</title>
446 <sect1><title>Fusion message devices</title>
447 !Edrivers/message/fusion/mptbase.c
448 !Idrivers/message/fusion/mptbase.c
449 !Edrivers/message/fusion/mptscsih.c
450 !Idrivers/message/fusion/mptscsih.c
451 !Idrivers/message/fusion/mptctl.c
452 !Idrivers/message/fusion/mptspi.c
453 !Idrivers/message/fusion/mptfc.c
454 !Idrivers/message/fusion/mptlan.c
456 <sect1><title>I2O message devices</title>
457 !Iinclude/linux/i2o.h
458 !Idrivers/message/i2o/core.h
459 !Edrivers/message/i2o/iop.c
460 !Idrivers/message/i2o/iop.c
461 !Idrivers/message/i2o/config-osm.c
462 !Edrivers/message/i2o/exec-osm.c
463 !Idrivers/message/i2o/exec-osm.c
464 !Idrivers/message/i2o/bus-osm.c
465 !Edrivers/message/i2o/device.c
466 !Idrivers/message/i2o/device.c
467 !Idrivers/message/i2o/driver.c
468 !Idrivers/message/i2o/pci.c
469 !Idrivers/message/i2o/i2o_block.c
470 !Idrivers/message/i2o/i2o_scsi.c
471 !Idrivers/message/i2o/i2o_proc.c
475 <chapter id="snddev">
476 <title>Sound Devices</title>
477 !Iinclude/sound/core.h
479 !Iinclude/sound/pcm.h
481 !Esound/core/device.c
483 !Esound/core/rawmidi.c
485 !Esound/core/memory.c
486 !Esound/core/pcm_memory.c
488 !Esound/core/isadma.c
489 !Esound/core/control.c
490 !Esound/core/pcm_lib.c
492 !Esound/core/pcm_native.c
493 !Esound/core/memalloc.c
494 <!-- FIXME: Removed for now since no structured comments in source
495 X!Isound/sound_firmware.c
499 <chapter id="uart16x50">
500 <title>16x50 UART Driver</title>
501 !Iinclude/linux/serial_core.h
502 !Edrivers/serial/serial_core.c
503 !Edrivers/serial/8250.c
506 <chapter id="z85230">
507 <title>Z85230 Support Library</title>
508 !Edrivers/net/wan/z85230.c
512 <title>Frame Buffer Library</title>
515 The frame buffer drivers depend heavily on four data structures.
516 These structures are declared in include/linux/fb.h. They are
517 fb_info, fb_var_screeninfo, fb_fix_screeninfo and fb_monospecs.
518 The last three can be made available to and from userland.
522 fb_info defines the current state of a particular video card.
523 Inside fb_info, there exists a fb_ops structure which is a
524 collection of needed functions to make fbdev and fbcon work.
525 fb_info is only visible to the kernel.
529 fb_var_screeninfo is used to describe the features of a video card
530 that are user defined. With fb_var_screeninfo, things such as
531 depth and the resolution may be defined.
535 The next structure is fb_fix_screeninfo. This defines the
536 properties of a card that are created when a mode is set and can't
537 be changed otherwise. A good example of this is the start of the
538 frame buffer memory. This "locks" the address of the frame buffer
539 memory, so that it cannot be changed or moved.
543 The last structure is fb_monospecs. In the old API, there was
544 little importance for fb_monospecs. This allowed for forbidden things
545 such as setting a mode of 800x600 on a fix frequency monitor. With
546 the new API, fb_monospecs prevents such things, and if used
547 correctly, can prevent a monitor from being cooked. fb_monospecs
548 will not be useful until kernels 2.5.x.
551 <sect1><title>Frame Buffer Memory</title>
552 !Edrivers/video/fbmem.c
555 <sect1><title>Frame Buffer Console</title>
556 X!Edrivers/video/console/fbcon.c
559 <sect1><title>Frame Buffer Colormap</title>
560 !Edrivers/video/fbcmap.c
563 drivers/video/fbgen.c has no docs, which stuffs up the sgml. Comment
564 out until somebody adds docs. KAO
565 <sect1><title>Frame Buffer Generic Functions</title>
566 X!Idrivers/video/fbgen.c
569 <sect1><title>Frame Buffer Video Mode Database</title>
570 !Idrivers/video/modedb.c
571 !Edrivers/video/modedb.c
573 <sect1><title>Frame Buffer Macintosh Video Mode Database</title>
574 !Edrivers/video/macmodes.c
576 <sect1><title>Frame Buffer Fonts</title>
578 Refer to the file drivers/video/console/fonts.c for more information.
580 <!-- FIXME: Removed for now since no structured comments in source
581 X!Idrivers/video/console/fonts.c
586 <chapter id="input_subsystem">
587 <title>Input Subsystem</title>
588 !Iinclude/linux/input.h
589 !Edrivers/input/input.c
590 !Edrivers/input/ff-core.c
591 !Edrivers/input/ff-memless.c
595 <title>Serial Peripheral Interface (SPI)</title>
597 SPI is the "Serial Peripheral Interface", widely used with
598 embedded systems because it is a simple and efficient
599 interface: basically a multiplexed shift register.
600 Its three signal wires hold a clock (SCK, often in the range
601 of 1-20 MHz), a "Master Out, Slave In" (MOSI) data line, and
602 a "Master In, Slave Out" (MISO) data line.
603 SPI is a full duplex protocol; for each bit shifted out the
604 MOSI line (one per clock) another is shifted in on the MISO line.
605 Those bits are assembled into words of various sizes on the
606 way to and from system memory.
607 An additional chipselect line is usually active-low (nCS);
608 four signals are normally used for each peripheral, plus
609 sometimes an interrupt.
612 The SPI bus facilities listed here provide a generalized
613 interface to declare SPI busses and devices, manage them
614 according to the standard Linux driver model, and perform
615 input/output operations.
616 At this time, only "master" side interfaces are supported,
617 where Linux talks to SPI peripherals and does not implement
618 such a peripheral itself.
619 (Interfaces to support implementing SPI slaves would
620 necessarily look different.)
623 The programming interface is structured around two kinds of driver,
624 and two kinds of device.
625 A "Controller Driver" abstracts the controller hardware, which may
626 be as simple as a set of GPIO pins or as complex as a pair of FIFOs
627 connected to dual DMA engines on the other side of the SPI shift
628 register (maximizing throughput). Such drivers bridge between
629 whatever bus they sit on (often the platform bus) and SPI, and
630 expose the SPI side of their device as a
631 <structname>struct spi_master</structname>.
632 SPI devices are children of that master, represented as a
633 <structname>struct spi_device</structname> and manufactured from
634 <structname>struct spi_board_info</structname> descriptors which
635 are usually provided by board-specific initialization code.
636 A <structname>struct spi_driver</structname> is called a
637 "Protocol Driver", and is bound to a spi_device using normal
641 The I/O model is a set of queued messages. Protocol drivers
642 submit one or more <structname>struct spi_message</structname>
643 objects, which are processed and completed asynchronously.
644 (There are synchronous wrappers, however.) Messages are
645 built from one or more <structname>struct spi_transfer</structname>
646 objects, each of which wraps a full duplex SPI transfer.
647 A variety of protocol tweaking options are needed, because
648 different chips adopt very different policies for how they
649 use the bits transferred with SPI.
651 !Iinclude/linux/spi/spi.h
652 !Fdrivers/spi/spi.c spi_register_board_info
657 <title>I<superscript>2</superscript>C and SMBus Subsystem</title>
660 I<superscript>2</superscript>C (or without fancy typography, "I2C")
661 is an acronym for the "Inter-IC" bus, a simple bus protocol which is
662 widely used where low data rate communications suffice.
663 Since it's also a licensed trademark, some vendors use another
664 name (such as "Two-Wire Interface", TWI) for the same bus.
665 I2C only needs two signals (SCL for clock, SDA for data), conserving
666 board real estate and minimizing signal quality issues.
667 Most I2C devices use seven bit addresses, and bus speeds of up
668 to 400 kHz; there's a high speed extension (3.4 MHz) that's not yet
670 I2C is a multi-master bus; open drain signaling is used to
671 arbitrate between masters, as well as to handshake and to
672 synchronize clocks from slower clients.
676 The Linux I2C programming interfaces support only the master
677 side of bus interactions, not the slave side.
678 The programming interface is structured around two kinds of driver,
679 and two kinds of device.
680 An I2C "Adapter Driver" abstracts the controller hardware; it binds
681 to a physical device (perhaps a PCI device or platform_device) and
682 exposes a <structname>struct i2c_adapter</structname> representing
683 each I2C bus segment it manages.
684 On each I2C bus segment will be I2C devices represented by a
685 <structname>struct i2c_client</structname>. Those devices will
686 be bound to a <structname>struct i2c_driver</structname>,
687 which should follow the standard Linux driver model.
688 (At this writing, a legacy model is more widely used.)
689 There are functions to perform various I2C protocol operations; at
690 this writing all such functions are usable only from task context.
694 The System Management Bus (SMBus) is a sibling protocol. Most SMBus
695 systems are also I2C conformant. The electrical constraints are
696 tighter for SMBus, and it standardizes particular protocol messages
697 and idioms. Controllers that support I2C can also support most
698 SMBus operations, but SMBus controllers don't support all the protocol
699 options that an I2C controller will.
700 There are functions to perform various SMBus protocol operations,
701 either using I2C primitives or by issuing SMBus commands to
702 i2c_adapter devices which don't support those I2C operations.
705 !Iinclude/linux/i2c.h
706 !Fdrivers/i2c/i2c-boardinfo.c i2c_register_board_info
707 !Edrivers/i2c/i2c-core.c
710 <chapter id="splice">
711 <title>splice API</title>
713 splice is a method for moving blocks of data around inside the
714 kernel, without continually transferring them between the kernel
721 <title>pipes API</title>
723 Pipe interfaces are all for in-kernel (builtin image) use.
724 They are not exported for use by modules.
726 !Iinclude/linux/pipe_fs_i.h