--- /dev/null
+<?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_32.h
+!Iarch/x86/include/asm/unaligned.h
+ </sect1>
+
+ <sect1><title>Delaying, scheduling, and timer routines</title>
+!Iinclude/linux/sched.h
+!Ekernel/sched.c
+!Ekernel/timer.c
+ </sect1>
+ <sect1><title>High-resolution timers</title>
+!Iinclude/linux/ktime.h
+!Iinclude/linux/hrtimer.h
+!Ekernel/hrtimer.c
+ </sect1>
+ <sect1><title>Workqueues and Kevents</title>
+!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.c
+!Ekernel/panic.c
+!Ekernel/sys.c
+!Ekernel/rcupdate.c
+ </sect1>
+
+ <sect1><title>Device Resource Management</title>
+!Edrivers/base/devres.c
+ </sect1>
+
+ </chapter>
+
+ <chapter id="devdrivers">
+ <title>Device drivers infrastructure</title>
+ <sect1><title>Device Drivers Base</title>
+<!--
+X!Iinclude/linux/device.h
+-->
+!Edrivers/base/driver.c
+!Edrivers/base/core.c
+!Edrivers/base/class.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/sys.c
+<!--
+X!Edrivers/base/interface.c
+-->
+!Edrivers/base/platform.c
+!Edrivers/base/bus.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>
+ <sect1><title>I2O message devices</title>
+!Iinclude/linux/i2o.h
+!Idrivers/message/i2o/core.h
+!Edrivers/message/i2o/iop.c
+!Idrivers/message/i2o/iop.c
+!Idrivers/message/i2o/config-osm.c
+!Edrivers/message/i2o/exec-osm.c
+!Idrivers/message/i2o/exec-osm.c
+!Idrivers/message/i2o/bus-osm.c
+!Edrivers/message/i2o/device.c
+!Idrivers/message/i2o/device.c
+!Idrivers/message/i2o/driver.c
+!Idrivers/message/i2o/pci.c
+!Idrivers/message/i2o/i2o_block.c
+!Idrivers/message/i2o/i2o_scsi.c
+!Idrivers/message/i2o/i2o_proc.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="uart16x50">
+ <title>16x50 UART Driver</title>
+!Iinclude/linux/serial_core.h
+!Edrivers/serial/serial_core.c
+!Edrivers/serial/8250.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/fbmem.c
+ </sect1>
+<!--
+ <sect1><title>Frame Buffer Console</title>
+X!Edrivers/video/console/fbcon.c
+ </sect1>
+-->
+ <sect1><title>Frame Buffer Colormap</title>
+!Edrivers/video/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/modedb.c
+!Edrivers/video/modedb.c
+ </sect1>
+ <sect1><title>Frame Buffer Macintosh Video Mode Database</title>
+!Edrivers/video/macmodes.c
+ </sect1>
+ <sect1><title>Frame Buffer Fonts</title>
+ <para>
+ Refer to the file drivers/video/console/fonts.c for more information.
+ </para>
+<!-- FIXME: Removed for now since no structured comments in source
+X!Idrivers/video/console/fonts.c
+-->
+ </sect1>
+ </chapter>
+
+ <chapter id="input_subsystem">
+ <title>Input Subsystem</title>
+!Iinclude/linux/input.h
+!Edrivers/input/input.c
+!Edrivers/input/ff-core.c
+!Edrivers/input/ff-memless.c
+ </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>
+
+</book>
<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_32.h
-!Iarch/x86/include/asm/unaligned.h
- </sect1>
-
- <sect1><title>Delaying, scheduling, and timer routines</title>
-!Iinclude/linux/sched.h
-!Ekernel/sched.c
-!Ekernel/timer.c
- </sect1>
- <sect1><title>High-resolution timers</title>
-!Iinclude/linux/ktime.h
-!Iinclude/linux/hrtimer.h
-!Ekernel/hrtimer.c
- </sect1>
- <sect1><title>Workqueues and Kevents</title>
-!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.c
-!Ekernel/panic.c
-!Ekernel/sys.c
-!Ekernel/rcupdate.c
- </sect1>
-
- <sect1><title>Device Resource Management</title>
-!Edrivers/base/devres.c
- </sect1>
-
- </chapter>
-
<chapter id="adt">
<title>Data Types</title>
<sect1><title>Doubly Linked Lists</title>
!Ikernel/acct.c
</chapter>
- <chapter id="devdrivers">
- <title>Device drivers infrastructure</title>
- <sect1><title>Device Drivers Base</title>
-<!--
-X!Iinclude/linux/device.h
--->
-!Edrivers/base/driver.c
-!Edrivers/base/core.c
-!Edrivers/base/class.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/sys.c
-<!--
-X!Edrivers/base/interface.c
--->
-!Edrivers/base/platform.c
-!Edrivers/base/bus.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="blkdev">
<title>Block Devices</title>
!Eblock/blk-core.c
!Edrivers/char/misc.c
</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>
- <sect1><title>I2O message devices</title>
-!Iinclude/linux/i2o.h
-!Idrivers/message/i2o/core.h
-!Edrivers/message/i2o/iop.c
-!Idrivers/message/i2o/iop.c
-!Idrivers/message/i2o/config-osm.c
-!Edrivers/message/i2o/exec-osm.c
-!Idrivers/message/i2o/exec-osm.c
-!Idrivers/message/i2o/bus-osm.c
-!Edrivers/message/i2o/device.c
-!Idrivers/message/i2o/device.c
-!Idrivers/message/i2o/driver.c
-!Idrivers/message/i2o/pci.c
-!Idrivers/message/i2o/i2o_block.c
-!Idrivers/message/i2o/i2o_scsi.c
-!Idrivers/message/i2o/i2o_proc.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="uart16x50">
- <title>16x50 UART Driver</title>
-!Iinclude/linux/serial_core.h
-!Edrivers/serial/serial_core.c
-!Edrivers/serial/8250.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/fbmem.c
- </sect1>
-<!--
- <sect1><title>Frame Buffer Console</title>
-X!Edrivers/video/console/fbcon.c
- </sect1>
--->
- <sect1><title>Frame Buffer Colormap</title>
-!Edrivers/video/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/modedb.c
-!Edrivers/video/modedb.c
- </sect1>
- <sect1><title>Frame Buffer Macintosh Video Mode Database</title>
-!Edrivers/video/macmodes.c
- </sect1>
- <sect1><title>Frame Buffer Fonts</title>
- <para>
- Refer to the file drivers/video/console/fonts.c for more information.
- </para>
-<!-- FIXME: Removed for now since no structured comments in source
-X!Idrivers/video/console/fonts.c
--->
- </sect1>
- </chapter>
-
- <chapter id="input_subsystem">
- <title>Input Subsystem</title>
-!Iinclude/linux/input.h
-!Edrivers/input/input.c
-!Edrivers/input/ff-core.c
-!Edrivers/input/ff-memless.c
- </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="clk">
<title>Clock Framework</title>
projects / GitHub / LineageOS / android_kernel_motorola_exynos9610.git / commitdiff