Documentation/DocBook/kernel-api.tmpl

   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="LinuxKernelAPI">
   6  <bookinfo>
   7   <title>The Linux Kernel API</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 !Iinclude/asm-i386/atomic.h
  49 !Iinclude/asm-i386/unaligned.h
  50      </sect1>
  51
  52      <sect1><title>Delaying, scheduling, and timer routines</title>
  53 !Iinclude/linux/sched.h
  54 !Ekernel/sched.c
  55 !Ekernel/timer.c
  56      </sect1>
  57      <sect1><title>High-resolution timers</title>
  58 !Iinclude/linux/ktime.h
  59 !Iinclude/linux/hrtimer.h
  60 !Ekernel/hrtimer.c
  61      </sect1>
  62      <sect1><title>Workqueues and Kevents</title>
  63 !Ekernel/workqueue.c
  64      </sect1>
  65      <sect1><title>Internal Functions</title>
  66 !Ikernel/exit.c
  67 !Ikernel/signal.c
  68 !Iinclude/linux/kthread.h
  69 !Ekernel/kthread.c
  70      </sect1>
  71
  72      <sect1><title>Kernel objects manipulation</title>
  73 <!--
  74 X!Iinclude/linux/kobject.h
  75 -->
  76 !Elib/kobject.c
  77      </sect1>
  78
  79      <sect1><title>Kernel utility functions</title>
  80 !Iinclude/linux/kernel.h
  81 !Ekernel/printk.c
  82 !Ekernel/panic.c
  83 !Ekernel/sys.c
  84 !Ekernel/rcupdate.c
  85      </sect1>
  86
  87      <sect1><title>Device Resource Management</title>
  88 !Edrivers/base/devres.c
  89      </sect1>
  90
  91   </chapter>
  92
  93   <chapter id="adt">
  94      <title>Data Types</title>
  95      <sect1><title>Doubly Linked Lists</title>
  96 !Iinclude/linux/list.h
  97      </sect1>
  98   </chapter>
  99
 100   <chapter id="libc">
 101      <title>Basic C Library Functions</title>
 102
 103      <para>
 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.
 109      </para>
 110
 111      <sect1><title>String Conversions</title>
 112 !Ilib/vsprintf.c
 113 !Elib/vsprintf.c
 114      </sect1>
 115      <sect1><title>String Manipulation</title>
 116 <!-- All functions are exported at now
 117 X!Ilib/string.c
 118  -->
 119 !Elib/string.c
 120      </sect1>
 121      <sect1><title>Bit Operations</title>
 122 !Iinclude/asm-i386/bitops.h
 123      </sect1>
 124   </chapter>
 125
 126   <chapter id="kernel-lib">
 127      <title>Basic Kernel Library Functions</title>
 128
 129      <para>
 130        The Linux kernel provides more basic utility functions.
 131      </para>
 132
 133      <sect1><title>Bitmap Operations</title>
 134 !Elib/bitmap.c
 135 !Ilib/bitmap.c
 136      </sect1>
 137
 138      <sect1><title>Command-line Parsing</title>
 139 !Elib/cmdline.c
 140      </sect1>
 141
 142      <sect1 id="crc"><title>CRC Functions</title>
 143 !Elib/crc7.c
 144 !Elib/crc16.c
 145 !Elib/crc-itu-t.c
 146 !Elib/crc32.c
 147 !Elib/crc-ccitt.c
 148      </sect1>
 149   </chapter>
 150
 151   <chapter id="mm">
 152      <title>Memory Management in Linux</title>
 153      <sect1><title>The Slab Cache</title>
 154 !Iinclude/linux/slab.h
 155 !Emm/slab.c
 156      </sect1>
 157      <sect1><title>User Space Memory Access</title>
 158 !Iinclude/asm-i386/uaccess.h
 159 !Earch/i386/lib/usercopy.c
 160      </sect1>
 161      <sect1><title>More Memory Management Functions</title>
 162 !Emm/readahead.c
 163 !Emm/filemap.c
 164 !Emm/memory.c
 165 !Emm/vmalloc.c
 166 !Imm/page_alloc.c
 167 !Emm/mempool.c
 168 !Emm/page-writeback.c
 169 !Emm/truncate.c
 170      </sect1>
 171   </chapter>
 172
 173
 174   <chapter id="ipc">
 175      <title>Kernel IPC facilities</title>
 176
 177      <sect1><title>IPC utilities</title>
 178 !Iipc/util.c
 179      </sect1>
 180   </chapter>
 181
 182   <chapter id="kfifo">
 183      <title>FIFO Buffer</title>
 184      <sect1><title>kfifo interface</title>
 185 !Iinclude/linux/kfifo.h
 186 !Ekernel/kfifo.c
 187      </sect1>
 188   </chapter>
 189
 190   <chapter id="relayfs">
 191      <title>relay interface support</title>
 192
 193      <para>
 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
 197         user space.
 198      </para>
 199
 200      <sect1><title>relay interface</title>
 201 !Ekernel/relay.c
 202 !Ikernel/relay.c
 203      </sect1>
 204   </chapter>
 205
 206   <chapter id="netcore">
 207      <title>Linux Networking</title>
 208      <sect1><title>Networking Base Types</title>
 209 !Iinclude/linux/net.h
 210      </sect1>
 211      <sect1><title>Socket Buffer Functions</title>
 212 !Iinclude/linux/skbuff.h
 213 !Iinclude/net/sock.h
 214 !Enet/socket.c
 215 !Enet/core/skbuff.c
 216 !Enet/core/sock.c
 217 !Enet/core/datagram.c
 218 !Enet/core/stream.c
 219      </sect1>
 220      <sect1><title>Socket Filter</title>
 221 !Enet/core/filter.c
 222      </sect1>
 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
 227      </sect1>
 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
 231 -->
 232 !Enet/sunrpc/xdr.c
 233 !Enet/sunrpc/svcsock.c
 234 !Enet/sunrpc/sched.c
 235      </sect1>
 236   </chapter>
 237
 238   <chapter id="netdev">
 239      <title>Network device support</title>
 240      <sect1><title>Driver Support</title>
 241 !Enet/core/dev.c
 242 !Enet/ethernet/eth.c
 243 !Iinclude/linux/etherdevice.h
 244 !Edrivers/net/phy/phy.c
 245 !Idrivers/net/phy/phy.c
 246 !Edrivers/net/phy/phy_device.c
 247 !Idrivers/net/phy/phy_device.c
 248 !Edrivers/net/phy/mdio_bus.c
 249 !Idrivers/net/phy/mdio_bus.c
 250 <!-- FIXME: Removed for now since no structured comments in source
 251 X!Enet/core/wireless.c
 252 -->
 253      </sect1>
 254      <sect1><title>Synchronous PPP</title>
 255 !Edrivers/net/wan/syncppp.c
 256      </sect1>
 257   </chapter>
 258
 259   <chapter id="modload">
 260      <title>Module Support</title>
 261      <sect1><title>Module Loading</title>
 262 !Ekernel/kmod.c
 263      </sect1>
 264      <sect1><title>Inter Module support</title>
 265         <para>
 266            Refer to the file kernel/module.c for more information.
 267         </para>
 268 <!-- FIXME: Removed for now since no structured comments in source
 269 X!Ekernel/module.c
 270 -->
 271      </sect1>
 272   </chapter>
 273
 274   <chapter id="hardware">
 275      <title>Hardware Interfaces</title>
 276      <sect1><title>Interrupt Handling</title>
 277 !Ekernel/irq/manage.c
 278      </sect1>
 279
 280      <sect1><title>DMA Channels</title>
 281 !Ekernel/dma.c
 282      </sect1>
 283
 284      <sect1><title>Resources Management</title>
 285 !Ikernel/resource.c
 286 !Ekernel/resource.c
 287      </sect1>
 288
 289      <sect1><title>MTRR Handling</title>
 290 !Earch/i386/kernel/cpu/mtrr/main.c
 291      </sect1>
 292
 293      <sect1><title>PCI Support Library</title>
 294 !Edrivers/pci/pci.c
 295 !Edrivers/pci/pci-driver.c
 296 !Edrivers/pci/remove.c
 297 !Edrivers/pci/pci-acpi.c
 298 !Edrivers/pci/search.c
 299 !Edrivers/pci/msi.c
 300 !Edrivers/pci/bus.c
 301 <!-- FIXME: Removed for now since no structured comments in source
 302 X!Edrivers/pci/hotplug.c
 303 -->
 304 !Edrivers/pci/probe.c
 305 !Edrivers/pci/rom.c
 306      </sect1>
 307      <sect1><title>PCI Hotplug Support Library</title>
 308 !Edrivers/pci/hotplug/pci_hotplug_core.c
 309      </sect1>
 310      <sect1><title>MCA Architecture</title>
 311         <sect2><title>MCA Device Functions</title>
 312            <para>
 313               Refer to the file arch/i386/kernel/mca.c for more information.
 314            </para>
 315 <!-- FIXME: Removed for now since no structured comments in source
 316 X!Earch/i386/kernel/mca.c
 317 -->
 318         </sect2>
 319         <sect2><title>MCA Bus DMA</title>
 320 !Iinclude/asm-i386/mca_dma.h
 321         </sect2>
 322      </sect1>
 323   </chapter>
 324
 325   <chapter id="firmware">
 326      <title>Firmware Interfaces</title>
 327      <sect1><title>DMI Interfaces</title>
 328 !Edrivers/firmware/dmi_scan.c
 329      </sect1>
 330      <sect1><title>EDD Interfaces</title>
 331 !Idrivers/firmware/edd.c
 332      </sect1>
 333   </chapter>
 334
 335   <chapter id="security">
 336      <title>Security Framework</title>
 337 !Esecurity/security.c
 338   </chapter>
 339
 340   <chapter id="audit">
 341      <title>Audit Interfaces</title>
 342 !Ekernel/audit.c
 343 !Ikernel/auditsc.c
 344 !Ikernel/auditfilter.c
 345   </chapter>
 346
 347   <chapter id="accounting">
 348      <title>Accounting Framework</title>
 349 !Ikernel/acct.c
 350   </chapter>
 351
 352   <chapter id="pmfuncs">
 353      <title>Power Management</title>
 354 !Ekernel/power/pm.c
 355   </chapter>
 356
 357   <chapter id="devdrivers">
 358      <title>Device drivers infrastructure</title>
 359      <sect1><title>Device Drivers Base</title>
 360 <!--
 361 X!Iinclude/linux/device.h
 362 -->
 363 !Edrivers/base/driver.c
 364 !Edrivers/base/core.c
 365 !Edrivers/base/class.c
 366 !Edrivers/base/firmware_class.c
 367 !Edrivers/base/transport_class.c
 368 !Edrivers/base/dmapool.c
 369 <!-- Cannot be included, because
 370      attribute_container_add_class_device_adapter
 371  and attribute_container_classdev_to_container
 372      exceed allowed 44 characters maximum
 373 X!Edrivers/base/attribute_container.c
 374 -->
 375 !Edrivers/base/sys.c
 376 <!--
 377 X!Edrivers/base/interface.c
 378 -->
 379 !Edrivers/base/platform.c
 380 !Edrivers/base/bus.c
 381      </sect1>
 382      <sect1><title>Device Drivers Power Management</title>
 383 !Edrivers/base/power/resume.c
 384 !Edrivers/base/power/suspend.c
 385      </sect1>
 386      <sect1><title>Device Drivers ACPI Support</title>
 387 <!-- Internal functions only
 388 X!Edrivers/acpi/sleep/main.c
 389 X!Edrivers/acpi/sleep/wakeup.c
 390 X!Edrivers/acpi/motherboard.c
 391 X!Edrivers/acpi/bus.c
 392 -->
 393 !Edrivers/acpi/scan.c
 394 !Idrivers/acpi/scan.c
 395 <!-- No correct structured comments
 396 X!Edrivers/acpi/pci_bind.c
 397 -->
 398      </sect1>
 399      <sect1><title>Device drivers PnP support</title>
 400 !Idrivers/pnp/core.c
 401 <!-- No correct structured comments
 402 X!Edrivers/pnp/system.c
 403  -->
 404 !Edrivers/pnp/card.c
 405 !Idrivers/pnp/driver.c
 406 !Edrivers/pnp/manager.c
 407 !Edrivers/pnp/support.c
 408      </sect1>
 409      <sect1><title>Userspace IO devices</title>
 410 !Edrivers/uio/uio.c
 411 !Iinclude/linux/uio_driver.h
 412      </sect1>
 413   </chapter>
 414
 415   <chapter id="blkdev">
 416      <title>Block Devices</title>
 417 !Eblock/ll_rw_blk.c
 418   </chapter>
 419
 420   <chapter id="chrdev">
 421         <title>Char devices</title>
 422 !Efs/char_dev.c
 423   </chapter>
 424
 425   <chapter id="miscdev">
 426      <title>Miscellaneous Devices</title>
 427 !Edrivers/char/misc.c
 428   </chapter>
 429
 430   <chapter id="parportdev">
 431      <title>Parallel Port Devices</title>
 432 !Iinclude/linux/parport.h
 433 !Edrivers/parport/ieee1284.c
 434 !Edrivers/parport/share.c
 435 !Idrivers/parport/daisy.c
 436   </chapter>
 437
 438   <chapter id="message_devices">
 439         <title>Message-based devices</title>
 440      <sect1><title>Fusion message devices</title>
 441 !Edrivers/message/fusion/mptbase.c
 442 !Idrivers/message/fusion/mptbase.c
 443 !Edrivers/message/fusion/mptscsih.c
 444 !Idrivers/message/fusion/mptscsih.c
 445 !Idrivers/message/fusion/mptctl.c
 446 !Idrivers/message/fusion/mptspi.c
 447 !Idrivers/message/fusion/mptfc.c
 448 !Idrivers/message/fusion/mptlan.c
 449      </sect1>
 450      <sect1><title>I2O message devices</title>
 451 !Iinclude/linux/i2o.h
 452 !Idrivers/message/i2o/core.h
 453 !Edrivers/message/i2o/iop.c
 454 !Idrivers/message/i2o/iop.c
 455 !Idrivers/message/i2o/config-osm.c
 456 !Edrivers/message/i2o/exec-osm.c
 457 !Idrivers/message/i2o/exec-osm.c
 458 !Idrivers/message/i2o/bus-osm.c
 459 !Edrivers/message/i2o/device.c
 460 !Idrivers/message/i2o/device.c
 461 !Idrivers/message/i2o/driver.c
 462 !Idrivers/message/i2o/pci.c
 463 !Idrivers/message/i2o/i2o_block.c
 464 !Idrivers/message/i2o/i2o_scsi.c
 465 !Idrivers/message/i2o/i2o_proc.c
 466      </sect1>
 467   </chapter>
 468
 469   <chapter id="snddev">
 470      <title>Sound Devices</title>
 471 !Iinclude/sound/core.h
 472 !Esound/sound_core.c
 473 !Iinclude/sound/pcm.h
 474 !Esound/core/pcm.c
 475 !Esound/core/device.c
 476 !Esound/core/info.c
 477 !Esound/core/rawmidi.c
 478 !Esound/core/sound.c
 479 !Esound/core/memory.c
 480 !Esound/core/pcm_memory.c
 481 !Esound/core/init.c
 482 !Esound/core/isadma.c
 483 !Esound/core/control.c
 484 !Esound/core/pcm_lib.c
 485 !Esound/core/hwdep.c
 486 !Esound/core/pcm_native.c
 487 !Esound/core/memalloc.c
 488 <!-- FIXME: Removed for now since no structured comments in source
 489 X!Isound/sound_firmware.c
 490 -->
 491   </chapter>
 492
 493   <chapter id="uart16x50">
 494      <title>16x50 UART Driver</title>
 495 !Iinclude/linux/serial_core.h
 496 !Edrivers/serial/serial_core.c
 497 !Edrivers/serial/8250.c
 498   </chapter>
 499
 500   <chapter id="z85230">
 501      <title>Z85230 Support Library</title>
 502 !Edrivers/net/wan/z85230.c
 503   </chapter>
 504
 505   <chapter id="fbdev">
 506      <title>Frame Buffer Library</title>
 507
 508      <para>
 509        The frame buffer drivers depend heavily on four data structures.
 510        These structures are declared in include/linux/fb.h.  They are
 511        fb_info, fb_var_screeninfo, fb_fix_screeninfo and fb_monospecs.
 512        The last three can be made available to and from userland.
 513      </para>
 514
 515      <para>
 516        fb_info defines the current state of a particular video card.
 517        Inside fb_info, there exists a fb_ops structure which is a
 518        collection of needed functions to make fbdev and fbcon work.
 519        fb_info is only visible to the kernel.
 520      </para>
 521
 522      <para>
 523        fb_var_screeninfo is used to describe the features of a video card
 524        that are user defined.  With fb_var_screeninfo, things such as
 525        depth and the resolution may be defined.
 526      </para>
 527
 528      <para>
 529        The next structure is fb_fix_screeninfo. This defines the
 530        properties of a card that are created when a mode is set and can't
 531        be changed otherwise.  A good example of this is the start of the
 532        frame buffer memory.  This "locks" the address of the frame buffer
 533        memory, so that it cannot be changed or moved.
 534      </para>
 535
 536      <para>
 537        The last structure is fb_monospecs. In the old API, there was
 538        little importance for fb_monospecs. This allowed for forbidden things
 539        such as setting a mode of 800x600 on a fix frequency monitor. With
 540        the new API, fb_monospecs prevents such things, and if used
 541        correctly, can prevent a monitor from being cooked.  fb_monospecs
 542        will not be useful until kernels 2.5.x.
 543      </para>
 544
 545      <sect1><title>Frame Buffer Memory</title>
 546 !Edrivers/video/fbmem.c
 547      </sect1>
 548 <!--
 549      <sect1><title>Frame Buffer Console</title>
 550 X!Edrivers/video/console/fbcon.c
 551      </sect1>
 552 -->
 553      <sect1><title>Frame Buffer Colormap</title>
 554 !Edrivers/video/fbcmap.c
 555      </sect1>
 556 <!-- FIXME:
 557   drivers/video/fbgen.c has no docs, which stuffs up the sgml.  Comment
 558   out until somebody adds docs.  KAO
 559      <sect1><title>Frame Buffer Generic Functions</title>
 560 X!Idrivers/video/fbgen.c
 561      </sect1>
 562 KAO -->
 563      <sect1><title>Frame Buffer Video Mode Database</title>
 564 !Idrivers/video/modedb.c
 565 !Edrivers/video/modedb.c
 566      </sect1>
 567      <sect1><title>Frame Buffer Macintosh Video Mode Database</title>
 568 !Edrivers/video/macmodes.c
 569      </sect1>
 570      <sect1><title>Frame Buffer Fonts</title>
 571         <para>
 572            Refer to the file drivers/video/console/fonts.c for more information.
 573         </para>
 574 <!-- FIXME: Removed for now since no structured comments in source
 575 X!Idrivers/video/console/fonts.c
 576 -->
 577      </sect1>
 578   </chapter>
 579
 580   <chapter id="input_subsystem">
 581      <title>Input Subsystem</title>
 582 !Iinclude/linux/input.h
 583 !Edrivers/input/input.c
 584 !Edrivers/input/ff-core.c
 585 !Edrivers/input/ff-memless.c
 586   </chapter>
 587
 588   <chapter id="spi">
 589       <title>Serial Peripheral Interface (SPI)</title>
 590   <para>
 591         SPI is the "Serial Peripheral Interface", widely used with
 592         embedded systems because it is a simple and efficient
 593         interface:  basically a multiplexed shift register.
 594         Its three signal wires hold a clock (SCK, often in the range
 595         of 1-20 MHz), a "Master Out, Slave In" (MOSI) data line, and
 596         a "Master In, Slave Out" (MISO) data line.
 597         SPI is a full duplex protocol; for each bit shifted out the
 598         MOSI line (one per clock) another is shifted in on the MISO line.
 599         Those bits are assembled into words of various sizes on the
 600         way to and from system memory.
 601         An additional chipselect line is usually active-low (nCS);
 602         four signals are normally used for each peripheral, plus
 603         sometimes an interrupt.
 604   </para>
 605   <para>
 606         The SPI bus facilities listed here provide a generalized
 607         interface to declare SPI busses and devices, manage them
 608         according to the standard Linux driver model, and perform
 609         input/output operations.
 610         At this time, only "master" side interfaces are supported,
 611         where Linux talks to SPI peripherals and does not implement
 612         such a peripheral itself.
 613         (Interfaces to support implementing SPI slaves would
 614         necessarily look different.)
 615   </para>
 616   <para>
 617         The programming interface is structured around two kinds of driver,
 618         and two kinds of device.
 619         A "Controller Driver" abstracts the controller hardware, which may
 620         be as simple as a set of GPIO pins or as complex as a pair of FIFOs
 621         connected to dual DMA engines on the other side of the SPI shift
 622         register (maximizing throughput).  Such drivers bridge between
 623         whatever bus they sit on (often the platform bus) and SPI, and
 624         expose the SPI side of their device as a
 625         <structname>struct spi_master</structname>.
 626         SPI devices are children of that master, represented as a
 627         <structname>struct spi_device</structname> and manufactured from
 628         <structname>struct spi_board_info</structname> descriptors which
 629         are usually provided by board-specific initialization code.
 630         A <structname>struct spi_driver</structname> is called a
 631         "Protocol Driver", and is bound to a spi_device using normal
 632         driver model calls.
 633   </para>
 634   <para>
 635         The I/O model is a set of queued messages.  Protocol drivers
 636         submit one or more <structname>struct spi_message</structname>
 637         objects, which are processed and completed asynchronously.
 638         (There are synchronous wrappers, however.)  Messages are
 639         built from one or more <structname>struct spi_transfer</structname>
 640         objects, each of which wraps a full duplex SPI transfer.
 641         A variety of protocol tweaking options are needed, because
 642         different chips adopt very different policies for how they
 643         use the bits transferred with SPI.
 644   </para>
 645 !Iinclude/linux/spi/spi.h
 646 !Fdrivers/spi/spi.c spi_register_board_info
 647 !Edrivers/spi/spi.c
 648   </chapter>
 649
 650   <chapter id="i2c">
 651      <title>I<superscript>2</superscript>C and SMBus Subsystem</title>
 652
 653      <para>
 654         I<superscript>2</superscript>C (or without fancy typography, "I2C")
 655         is an acronym for the "Inter-IC" bus, a simple bus protocol which is
 656         widely used where low data rate communications suffice.
 657         Since it's also a licensed trademark, some vendors use another
 658         name (such as "Two-Wire Interface", TWI) for the same bus.
 659         I2C only needs two signals (SCL for clock, SDA for data), conserving
 660         board real estate and minimizing signal quality issues.
 661         Most I2C devices use seven bit addresses, and bus speeds of up
 662         to 400 kHz; there's a high speed extension (3.4 MHz) that's not yet
 663         found wide use.
 664         I2C is a multi-master bus; open drain signaling is used to
 665         arbitrate between masters, as well as to handshake and to
 666         synchronize clocks from slower clients.
 667      </para>
 668
 669      <para>
 670         The Linux I2C programming interfaces support only the master
 671         side of bus interactions, not the slave side.
 672         The programming interface is structured around two kinds of driver,
 673         and two kinds of device.
 674         An I2C "Adapter Driver" abstracts the controller hardware; it binds
 675         to a physical device (perhaps a PCI device or platform_device) and
 676         exposes a <structname>struct i2c_adapter</structname> representing
 677         each I2C bus segment it manages.
 678         On each I2C bus segment will be I2C devices represented by a
 679         <structname>struct i2c_client</structname>.  Those devices will
 680         be bound to a <structname>struct i2c_driver</structname>,
 681         which should follow the standard Linux driver model.
 682         (At this writing, a legacy model is more widely used.)
 683         There are functions to perform various I2C protocol operations; at
 684         this writing all such functions are usable only from task context.
 685      </para>
 686
 687      <para>
 688         The System Management Bus (SMBus) is a sibling protocol.  Most SMBus
 689         systems are also I2C conformant.  The electrical constraints are
 690         tighter for SMBus, and it standardizes particular protocol messages
 691         and idioms.  Controllers that support I2C can also support most
 692         SMBus operations, but SMBus controllers don't support all the protocol
 693         options that an I2C controller will.
 694         There are functions to perform various SMBus protocol operations,
 695         either using I2C primitives or by issuing SMBus commands to
 696         i2c_adapter devices which don't support those I2C operations.
 697      </para>
 698
 699 !Iinclude/linux/i2c.h
 700 !Fdrivers/i2c/i2c-boardinfo.c i2c_register_board_info
 701 !Edrivers/i2c/i2c-core.c
 702   </chapter>
 703
 704   <chapter id="splice">
 705       <title>splice API</title>
 706   <para>
 707         splice is a method for moving blocks of data around inside the
 708         kernel, without continually transferring them between the kernel
 709         and user space.
 710   </para>
 711 !Ffs/splice.c
 712   </chapter>
 713
 714   <chapter id="pipes">
 715       <title>pipes API</title>
 716   <para>
 717         Pipe interfaces are all for in-kernel (builtin image) use.
 718         They are not exported for use by modules.
 719   </para>
 720 !Iinclude/linux/pipe_fs_i.h
 721 !Ffs/pipe.c
 722   </chapter>
 723
 724 </book>