diff options
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/DocBook/Makefile | 2 | ||||
| -rw-r--r-- | Documentation/DocBook/device-drivers.tmpl | 418 | ||||
| -rw-r--r-- | Documentation/DocBook/kernel-api.tmpl | 377 |
3 files changed, 419 insertions, 378 deletions
diff --git a/Documentation/DocBook/Makefile b/Documentation/DocBook/Makefile index dc3154e49279..1462ed86d40a 100644 --- a/Documentation/DocBook/Makefile +++ b/Documentation/DocBook/Makefile @@ -6,7 +6,7 @@ # To add a new book the only step required is to add the book to the # list of DOCBOOKS. -DOCBOOKS := z8530book.xml mcabook.xml \ +DOCBOOKS := z8530book.xml mcabook.xml device-drivers.xml \ kernel-hacking.xml kernel-locking.xml deviceiobook.xml \ procfs-guide.xml writing_usb_driver.xml networking.xml \ kernel-api.xml filesystems.xml lsm.xml usb.xml kgdb.xml \ diff --git a/Documentation/DocBook/device-drivers.tmpl b/Documentation/DocBook/device-drivers.tmpl new file mode 100644 index 000000000000..94a20fe8fedf --- /dev/null +++ b/Documentation/DocBook/device-drivers.tmpl @@ -0,0 +1,418 @@ +<?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> diff --git a/Documentation/DocBook/kernel-api.tmpl b/Documentation/DocBook/kernel-api.tmpl index 5818ff75786a..bc962cda6504 100644 --- a/Documentation/DocBook/kernel-api.tmpl +++ b/Documentation/DocBook/kernel-api.tmpl @@ -38,58 +38,6 @@ <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> @@ -298,62 +246,6 @@ X!Earch/x86/kernel/mca_32.c !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 @@ -381,275 +273,6 @@ X!Edrivers/pnp/system.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> |