Documentation/DocBook/kernel-api.tmpl

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