123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199200201202203204205206207208209210211212213214215216217218219220221222223224225226227228229230231232233234235236237238239240241242243244245246247248249250251252253254255256257258259260261262263264265266267268269270271272273274275276277278279280281282283284285286287288289290291292293294295296297298299300301302303304305306307308309310311312313314315316317318319320321322323324325326327328329330331332333334335336337338339340341342343344345346347348349350351352353354355356357358359360361362363364365366367368369370371372373374375376377378379380381382383384385386387388389390391392393394395396397398399400401402403404405406407408409410411412413414415416417418419420421422423424425426427428429430431432433434435436437438439440441442443444445446447448449450451452453454455456457458459460461462463464465466467468469470471472473474475476477478479480481482483484485486487488489490491492493494495496497498499500501502503504505506507508509510511512513514515516517518519520521522523524525526527528529530531532533534535536537538539540541542543544545546547548549550551552553554555556557558559560561562563564565566567568569570571572573574575576577578579580581582583584585586587588589590591 |
- <?xml version="1.0" encoding="UTF-8"?>
- <!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
- "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" []>
- <book id="LinuxDriversAPI">
- <bookinfo>
- <title>Linux Device Drivers</title>
- <legalnotice>
- <para>
- This documentation is free software; you can redistribute
- it and/or modify it under the terms of the GNU General Public
- License as published by the Free Software Foundation; either
- version 2 of the License, or (at your option) any later
- version.
- </para>
- <para>
- This program is distributed in the hope that it will be
- useful, but WITHOUT ANY WARRANTY; without even the implied
- warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
- See the GNU General Public License for more details.
- </para>
- <para>
- You should have received a copy of the GNU General Public
- License along with this program; if not, write to the Free
- Software Foundation, Inc., 59 Temple Place, Suite 330, Boston,
- MA 02111-1307 USA
- </para>
- <para>
- For more details see the file COPYING in the source
- distribution of Linux.
- </para>
- </legalnotice>
- </bookinfo>
- <toc></toc>
- <chapter id="Basics">
- <title>Driver Basics</title>
- <sect1><title>Driver Entry and Exit points</title>
- !Iinclude/linux/init.h
- </sect1>
- <sect1><title>Atomic and pointer manipulation</title>
- !Iarch/x86/include/asm/atomic.h
- </sect1>
- <sect1><title>Delaying, scheduling, and timer routines</title>
- !Iinclude/linux/sched.h
- !Ekernel/sched/core.c
- !Ikernel/sched/cpupri.c
- !Ikernel/sched/fair.c
- !Iinclude/linux/completion.h
- !Ekernel/time/timer.c
- </sect1>
- <sect1><title>Wait queues and Wake events</title>
- !Iinclude/linux/wait.h
- !Ekernel/sched/wait.c
- </sect1>
- <sect1><title>High-resolution timers</title>
- !Iinclude/linux/ktime.h
- !Iinclude/linux/hrtimer.h
- !Ekernel/time/hrtimer.c
- </sect1>
- <sect1><title>Workqueues and Kevents</title>
- !Iinclude/linux/workqueue.h
- !Ekernel/workqueue.c
- </sect1>
- <sect1><title>Internal Functions</title>
- !Ikernel/exit.c
- !Ikernel/signal.c
- !Iinclude/linux/kthread.h
- !Ekernel/kthread.c
- </sect1>
- <sect1><title>Kernel objects manipulation</title>
- <!--
- X!Iinclude/linux/kobject.h
- -->
- !Elib/kobject.c
- </sect1>
- <sect1><title>Kernel utility functions</title>
- !Iinclude/linux/kernel.h
- !Ekernel/printk/printk.c
- !Ekernel/panic.c
- !Ekernel/sys.c
- !Ekernel/rcu/srcu.c
- !Ekernel/rcu/tree.c
- !Ekernel/rcu/tree_plugin.h
- !Ekernel/rcu/update.c
- </sect1>
- <sect1><title>Device Resource Management</title>
- !Edrivers/base/devres.c
- </sect1>
- </chapter>
- <chapter id="devdrivers">
- <title>Device drivers infrastructure</title>
- <sect1><title>The Basic Device Driver-Model Structures </title>
- !Iinclude/linux/device.h
- </sect1>
- <sect1><title>Device Drivers Base</title>
- !Idrivers/base/init.c
- !Edrivers/base/driver.c
- !Edrivers/base/core.c
- !Edrivers/base/syscore.c
- !Edrivers/base/class.c
- !Idrivers/base/node.c
- !Edrivers/base/firmware_class.c
- !Edrivers/base/transport_class.c
- <!-- Cannot be included, because
- attribute_container_add_class_device_adapter
- and attribute_container_classdev_to_container
- exceed allowed 44 characters maximum
- X!Edrivers/base/attribute_container.c
- -->
- !Edrivers/base/dd.c
- <!--
- X!Edrivers/base/interface.c
- -->
- !Iinclude/linux/platform_device.h
- !Edrivers/base/platform.c
- !Edrivers/base/bus.c
- </sect1>
- <sect1><title>Device Drivers DMA Management</title>
- !Edrivers/dma-buf/dma-buf.c
- !Edrivers/dma-buf/fence.c
- !Edrivers/dma-buf/seqno-fence.c
- !Iinclude/linux/fence.h
- !Iinclude/linux/seqno-fence.h
- !Edrivers/dma-buf/reservation.c
- !Iinclude/linux/reservation.h
- !Edrivers/base/dma-coherent.c
- !Edrivers/base/dma-mapping.c
- </sect1>
- <sect1><title>Device Drivers Power Management</title>
- !Edrivers/base/power/main.c
- </sect1>
- <sect1><title>Device Drivers ACPI Support</title>
- <!-- Internal functions only
- X!Edrivers/acpi/sleep/main.c
- X!Edrivers/acpi/sleep/wakeup.c
- X!Edrivers/acpi/motherboard.c
- X!Edrivers/acpi/bus.c
- -->
- !Edrivers/acpi/scan.c
- !Idrivers/acpi/scan.c
- <!-- No correct structured comments
- X!Edrivers/acpi/pci_bind.c
- -->
- </sect1>
- <sect1><title>Device drivers PnP support</title>
- !Idrivers/pnp/core.c
- <!-- No correct structured comments
- X!Edrivers/pnp/system.c
- -->
- !Edrivers/pnp/card.c
- !Idrivers/pnp/driver.c
- !Edrivers/pnp/manager.c
- !Edrivers/pnp/support.c
- </sect1>
- <sect1><title>Userspace IO devices</title>
- !Edrivers/uio/uio.c
- !Iinclude/linux/uio_driver.h
- </sect1>
- </chapter>
- <chapter id="parportdev">
- <title>Parallel Port Devices</title>
- !Iinclude/linux/parport.h
- !Edrivers/parport/ieee1284.c
- !Edrivers/parport/share.c
- !Idrivers/parport/daisy.c
- </chapter>
- <chapter id="message_devices">
- <title>Message-based devices</title>
- <sect1><title>Fusion message devices</title>
- !Edrivers/message/fusion/mptbase.c
- !Idrivers/message/fusion/mptbase.c
- !Edrivers/message/fusion/mptscsih.c
- !Idrivers/message/fusion/mptscsih.c
- !Idrivers/message/fusion/mptctl.c
- !Idrivers/message/fusion/mptspi.c
- !Idrivers/message/fusion/mptfc.c
- !Idrivers/message/fusion/mptlan.c
- </sect1>
- </chapter>
- <chapter id="snddev">
- <title>Sound Devices</title>
- !Iinclude/sound/core.h
- !Esound/sound_core.c
- !Iinclude/sound/pcm.h
- !Esound/core/pcm.c
- !Esound/core/device.c
- !Esound/core/info.c
- !Esound/core/rawmidi.c
- !Esound/core/sound.c
- !Esound/core/memory.c
- !Esound/core/pcm_memory.c
- !Esound/core/init.c
- !Esound/core/isadma.c
- !Esound/core/control.c
- !Esound/core/pcm_lib.c
- !Esound/core/hwdep.c
- !Esound/core/pcm_native.c
- !Esound/core/memalloc.c
- <!-- FIXME: Removed for now since no structured comments in source
- X!Isound/sound_firmware.c
- -->
- </chapter>
- <chapter id="mediadev">
- <title>Media Devices</title>
- <sect1><title>Video2Linux devices</title>
- !Iinclude/media/tuner.h
- !Iinclude/media/tuner-types.h
- !Iinclude/media/tveeprom.h
- !Iinclude/media/v4l2-async.h
- !Iinclude/media/v4l2-ctrls.h
- !Iinclude/media/v4l2-dv-timings.h
- !Iinclude/media/v4l2-event.h
- !Iinclude/media/v4l2-flash-led-class.h
- !Iinclude/media/v4l2-mediabus.h
- !Iinclude/media/v4l2-mem2mem.h
- !Iinclude/media/v4l2-of.h
- !Iinclude/media/v4l2-subdev.h
- !Iinclude/media/videobuf2-core.h
- !Iinclude/media/videobuf2-v4l2.h
- !Iinclude/media/videobuf2-memops.h
- </sect1>
- <sect1><title>Digital TV (DVB) devices</title>
- !Idrivers/media/dvb-core/dvb_ca_en50221.h
- !Idrivers/media/dvb-core/dvb_frontend.h
- !Idrivers/media/dvb-core/dvb_math.h
- !Idrivers/media/dvb-core/dvb_ringbuffer.h
- !Idrivers/media/dvb-core/dvbdev.h
- <sect1><title>Digital TV Demux API</title>
- <para>The kernel demux API defines a driver-internal interface for
- registering low-level, hardware specific driver to a hardware
- independent demux layer. It is only of interest for Digital TV
- device driver writers. The header file for this API is named
- <constant>demux.h</constant> and located in
- <constant>drivers/media/dvb-core</constant>.</para>
- <para>The demux API should be implemented for each demux in the
- system. It is used to select the TS source of a demux and to manage
- the demux resources. When the demux client allocates a resource via
- the demux API, it receives a pointer to the API of that
- resource.</para>
- <para>Each demux receives its TS input from a DVB front-end or from
- memory, as set via this demux API. In a system with more than one
- front-end, the API can be used to select one of the DVB front-ends
- as a TS source for a demux, unless this is fixed in the HW platform.
- The demux API only controls front-ends regarding to their connections
- with demuxes; the APIs used to set the other front-end parameters,
- such as tuning, are not defined in this document.</para>
- <para>The functions that implement the abstract interface demux should
- be defined static or module private and registered to the Demux
- core for external access. It is not necessary to implement every
- function in the struct <constant>dmx_demux</constant>. For example,
- a demux interface might support Section filtering, but not PES
- filtering. The API client is expected to check the value of any
- function pointer before calling the function: the value of NULL means
- that the “function is not available”.</para>
- <para>Whenever the functions of the demux API modify shared data,
- the possibilities of lost update and race condition problems should
- be addressed, e.g. by protecting parts of code with mutexes.</para>
- <para>Note that functions called from a bottom half context must not
- sleep. Even a simple memory allocation without using GFP_ATOMIC can
- result in a kernel thread being put to sleep if swapping is needed.
- For example, the Linux kernel calls the functions of a network device
- interface from a bottom half context. Thus, if a demux API function
- is called from network device code, the function must not sleep.
- </para>
- </sect1>
- <section id="demux_callback_api">
- <title>Demux Callback API</title>
- <para>This kernel-space API comprises the callback functions that
- deliver filtered data to the demux client. Unlike the other DVB
- kABIs, these functions are provided by the client and called from
- the demux code.</para>
- <para>The function pointers of this abstract interface are not
- packed into a structure as in the other demux APIs, because the
- callback functions are registered and used independent of each
- other. As an example, it is possible for the API client to provide
- several callback functions for receiving TS packets and no
- callbacks for PES packets or sections.</para>
- <para>The functions that implement the callback API need not be
- re-entrant: when a demux driver calls one of these functions,
- the driver is not allowed to call the function again before
- the original call returns. If a callback is triggered by a
- hardware interrupt, it is recommended to use the Linux
- “bottom half” mechanism or start a tasklet instead of
- making the callback function call directly from a hardware
- interrupt.</para>
- <para>This mechanism is implemented by
- <link linkend='API-dmx-ts-cb'>dmx_ts_cb()</link> and
- <link linkend='API-dmx-section-cb'>dmx_section_cb()</link>.</para>
- </section>
- !Idrivers/media/dvb-core/demux.h
- </sect1>
- <sect1><title>Remote Controller devices</title>
- !Iinclude/media/rc-core.h
- !Iinclude/media/lirc_dev.h
- </sect1>
- <sect1><title>Media Controller devices</title>
- !Iinclude/media/media-device.h
- !Iinclude/media/media-devnode.h
- !Iinclude/media/media-entity.h
- </sect1>
- </chapter>
- <chapter id="uart16x50">
- <title>16x50 UART Driver</title>
- !Edrivers/tty/serial/serial_core.c
- !Edrivers/tty/serial/8250/8250_core.c
- </chapter>
- <chapter id="fbdev">
- <title>Frame Buffer Library</title>
- <para>
- The frame buffer drivers depend heavily on four data structures.
- These structures are declared in include/linux/fb.h. They are
- fb_info, fb_var_screeninfo, fb_fix_screeninfo and fb_monospecs.
- The last three can be made available to and from userland.
- </para>
- <para>
- fb_info defines the current state of a particular video card.
- Inside fb_info, there exists a fb_ops structure which is a
- collection of needed functions to make fbdev and fbcon work.
- fb_info is only visible to the kernel.
- </para>
- <para>
- fb_var_screeninfo is used to describe the features of a video card
- that are user defined. With fb_var_screeninfo, things such as
- depth and the resolution may be defined.
- </para>
- <para>
- The next structure is fb_fix_screeninfo. This defines the
- properties of a card that are created when a mode is set and can't
- be changed otherwise. A good example of this is the start of the
- frame buffer memory. This "locks" the address of the frame buffer
- memory, so that it cannot be changed or moved.
- </para>
- <para>
- The last structure is fb_monospecs. In the old API, there was
- little importance for fb_monospecs. This allowed for forbidden things
- such as setting a mode of 800x600 on a fix frequency monitor. With
- the new API, fb_monospecs prevents such things, and if used
- correctly, can prevent a monitor from being cooked. fb_monospecs
- will not be useful until kernels 2.5.x.
- </para>
- <sect1><title>Frame Buffer Memory</title>
- !Edrivers/video/fbdev/core/fbmem.c
- </sect1>
- <!--
- <sect1><title>Frame Buffer Console</title>
- X!Edrivers/video/console/fbcon.c
- </sect1>
- -->
- <sect1><title>Frame Buffer Colormap</title>
- !Edrivers/video/fbdev/core/fbcmap.c
- </sect1>
- <!-- FIXME:
- drivers/video/fbgen.c has no docs, which stuffs up the sgml. Comment
- out until somebody adds docs. KAO
- <sect1><title>Frame Buffer Generic Functions</title>
- X!Idrivers/video/fbgen.c
- </sect1>
- KAO -->
- <sect1><title>Frame Buffer Video Mode Database</title>
- !Idrivers/video/fbdev/core/modedb.c
- !Edrivers/video/fbdev/core/modedb.c
- </sect1>
- <sect1><title>Frame Buffer Macintosh Video Mode Database</title>
- !Edrivers/video/fbdev/macmodes.c
- </sect1>
- <sect1><title>Frame Buffer Fonts</title>
- <para>
- Refer to the file lib/fonts/fonts.c for more information.
- </para>
- <!-- FIXME: Removed for now since no structured comments in source
- X!Ilib/fonts/fonts.c
- -->
- </sect1>
- </chapter>
- <chapter id="input_subsystem">
- <title>Input Subsystem</title>
- <sect1><title>Input core</title>
- !Iinclude/linux/input.h
- !Edrivers/input/input.c
- !Edrivers/input/ff-core.c
- !Edrivers/input/ff-memless.c
- </sect1>
- <sect1><title>Multitouch Library</title>
- !Iinclude/linux/input/mt.h
- !Edrivers/input/input-mt.c
- </sect1>
- <sect1><title>Polled input devices</title>
- !Iinclude/linux/input-polldev.h
- !Edrivers/input/input-polldev.c
- </sect1>
- <sect1><title>Matrix keyboars/keypads</title>
- !Iinclude/linux/input/matrix_keypad.h
- </sect1>
- <sect1><title>Sparse keymap support</title>
- !Iinclude/linux/input/sparse-keymap.h
- !Edrivers/input/sparse-keymap.c
- </sect1>
- </chapter>
- <chapter id="spi">
- <title>Serial Peripheral Interface (SPI)</title>
- <para>
- SPI is the "Serial Peripheral Interface", widely used with
- embedded systems because it is a simple and efficient
- interface: basically a multiplexed shift register.
- Its three signal wires hold a clock (SCK, often in the range
- of 1-20 MHz), a "Master Out, Slave In" (MOSI) data line, and
- a "Master In, Slave Out" (MISO) data line.
- SPI is a full duplex protocol; for each bit shifted out the
- MOSI line (one per clock) another is shifted in on the MISO line.
- Those bits are assembled into words of various sizes on the
- way to and from system memory.
- An additional chipselect line is usually active-low (nCS);
- four signals are normally used for each peripheral, plus
- sometimes an interrupt.
- </para>
- <para>
- The SPI bus facilities listed here provide a generalized
- interface to declare SPI busses and devices, manage them
- according to the standard Linux driver model, and perform
- input/output operations.
- At this time, only "master" side interfaces are supported,
- where Linux talks to SPI peripherals and does not implement
- such a peripheral itself.
- (Interfaces to support implementing SPI slaves would
- necessarily look different.)
- </para>
- <para>
- The programming interface is structured around two kinds of driver,
- and two kinds of device.
- A "Controller Driver" abstracts the controller hardware, which may
- be as simple as a set of GPIO pins or as complex as a pair of FIFOs
- connected to dual DMA engines on the other side of the SPI shift
- register (maximizing throughput). Such drivers bridge between
- whatever bus they sit on (often the platform bus) and SPI, and
- expose the SPI side of their device as a
- <structname>struct spi_master</structname>.
- SPI devices are children of that master, represented as a
- <structname>struct spi_device</structname> and manufactured from
- <structname>struct spi_board_info</structname> descriptors which
- are usually provided by board-specific initialization code.
- A <structname>struct spi_driver</structname> is called a
- "Protocol Driver", and is bound to a spi_device using normal
- driver model calls.
- </para>
- <para>
- The I/O model is a set of queued messages. Protocol drivers
- submit one or more <structname>struct spi_message</structname>
- objects, which are processed and completed asynchronously.
- (There are synchronous wrappers, however.) Messages are
- built from one or more <structname>struct spi_transfer</structname>
- objects, each of which wraps a full duplex SPI transfer.
- A variety of protocol tweaking options are needed, because
- different chips adopt very different policies for how they
- use the bits transferred with SPI.
- </para>
- !Iinclude/linux/spi/spi.h
- !Fdrivers/spi/spi.c spi_register_board_info
- !Edrivers/spi/spi.c
- </chapter>
- <chapter id="i2c">
- <title>I<superscript>2</superscript>C and SMBus Subsystem</title>
- <para>
- I<superscript>2</superscript>C (or without fancy typography, "I2C")
- is an acronym for the "Inter-IC" bus, a simple bus protocol which is
- widely used where low data rate communications suffice.
- Since it's also a licensed trademark, some vendors use another
- name (such as "Two-Wire Interface", TWI) for the same bus.
- I2C only needs two signals (SCL for clock, SDA for data), conserving
- board real estate and minimizing signal quality issues.
- Most I2C devices use seven bit addresses, and bus speeds of up
- to 400 kHz; there's a high speed extension (3.4 MHz) that's not yet
- found wide use.
- I2C is a multi-master bus; open drain signaling is used to
- arbitrate between masters, as well as to handshake and to
- synchronize clocks from slower clients.
- </para>
- <para>
- The Linux I2C programming interfaces support only the master
- side of bus interactions, not the slave side.
- The programming interface is structured around two kinds of driver,
- and two kinds of device.
- An I2C "Adapter Driver" abstracts the controller hardware; it binds
- to a physical device (perhaps a PCI device or platform_device) and
- exposes a <structname>struct i2c_adapter</structname> representing
- each I2C bus segment it manages.
- On each I2C bus segment will be I2C devices represented by a
- <structname>struct i2c_client</structname>. Those devices will
- be bound to a <structname>struct i2c_driver</structname>,
- which should follow the standard Linux driver model.
- (At this writing, a legacy model is more widely used.)
- There are functions to perform various I2C protocol operations; at
- this writing all such functions are usable only from task context.
- </para>
- <para>
- The System Management Bus (SMBus) is a sibling protocol. Most SMBus
- systems are also I2C conformant. The electrical constraints are
- tighter for SMBus, and it standardizes particular protocol messages
- and idioms. Controllers that support I2C can also support most
- SMBus operations, but SMBus controllers don't support all the protocol
- options that an I2C controller will.
- There are functions to perform various SMBus protocol operations,
- either using I2C primitives or by issuing SMBus commands to
- i2c_adapter devices which don't support those I2C operations.
- </para>
- !Iinclude/linux/i2c.h
- !Fdrivers/i2c/i2c-boardinfo.c i2c_register_board_info
- !Edrivers/i2c/i2c-core.c
- </chapter>
- <chapter id="hsi">
- <title>High Speed Synchronous Serial Interface (HSI)</title>
- <para>
- High Speed Synchronous Serial Interface (HSI) is a
- serial interface mainly used for connecting application
- engines (APE) with cellular modem engines (CMT) in cellular
- handsets.
- HSI provides multiplexing for up to 16 logical channels,
- low-latency and full duplex communication.
- </para>
- !Iinclude/linux/hsi/hsi.h
- !Edrivers/hsi/hsi.c
- </chapter>
- <chapter id="pwm">
- <title>Pulse-Width Modulation (PWM)</title>
- <para>
- Pulse-width modulation is a modulation technique primarily used to
- control power supplied to electrical devices.
- </para>
- <para>
- The PWM framework provides an abstraction for providers and consumers
- of PWM signals. A controller that provides one or more PWM signals is
- registered as <structname>struct pwm_chip</structname>. Providers are
- expected to embed this structure in a driver-specific structure. This
- structure contains fields that describe a particular chip.
- </para>
- <para>
- A chip exposes one or more PWM signal sources, each of which exposed
- as a <structname>struct pwm_device</structname>. Operations can be
- performed on PWM devices to control the period, duty cycle, polarity
- and active state of the signal.
- </para>
- <para>
- Note that PWM devices are exclusive resources: they can always only be
- used by one consumer at a time.
- </para>
- !Iinclude/linux/pwm.h
- !Edrivers/pwm/core.c
- </chapter>
- </book>
|