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authorLinus Torvalds <torvalds@woody.linux-foundation.org>2007-07-12 13:25:00 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-07-12 13:25:00 -0700
commit068345f4a873e8b0b511e8f94a595a20e176eeff (patch)
treef67503164f017b45ab425827d71fb7d23920a519 /Documentation/DocBook
parentc39736823232bc3ca113c8228fa852c09fba300e (diff)
parent0a85e9a271a754e352af8a8b625025017fd97449 (diff)
Merge branch 'i2c-for-linus' of git://jdelvare.pck.nerim.net/jdelvare-2.6
* 'i2c-for-linus' of git://jdelvare.pck.nerim.net/jdelvare-2.6: (26 commits) i2c-rpx: Remove i2c-mpc: work around missing-9th-clock-pulse bug i2c: New PMC MSP71xx TWI bus driver i2c-savage4: Delete many unused defines i2c/tsl2550: Speed up initialization i2c: New bus driver for the TAOS evaluation modules i2c-i801: Use the internal 32-byte buffer on ICH4+ i2c-i801: Various cleanups i2c: Add support for the TSL2550 i2c-pxa: Support new-style I2C drivers i2c-gpio: Make some internal functions static i2c-gpio: Add support for new-style clients i2c-iop3xx: Switch to static adapter numbering i2c-sis5595: Resolve resource conflict with sis5595 matroxfb: Clean-up i2c header inclusions i2c-nforce2: Add support for SMBus block transactions i2c-mpc: Use i2c_add_numbered_adapter i2c-mv64xxx: Use i2c_add_numbered_adapter i2c-piix4: Add support for the ATI SB700 i2c: New DS1682 chip driver ...
Diffstat (limited to 'Documentation/DocBook')
-rw-r--r--Documentation/DocBook/kernel-api.tmpl55
1 files changed, 55 insertions, 0 deletions
diff --git a/Documentation/DocBook/kernel-api.tmpl b/Documentation/DocBook/kernel-api.tmpl
index 8c5698a8c2e..46bcff2849b 100644
--- a/Documentation/DocBook/kernel-api.tmpl
+++ b/Documentation/DocBook/kernel-api.tmpl
@@ -643,6 +643,60 @@ X!Idrivers/video/console/fonts.c
!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="splice">
<title>splice API</title>
<para>)
@@ -654,4 +708,5 @@ X!Idrivers/video/console/fonts.c
!Ffs/splice.c
</chapter>
+
</book>