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author | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-07-12 13:25:00 -0700 |
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committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-07-12 13:25:00 -0700 |
commit | 068345f4a873e8b0b511e8f94a595a20e176eeff (patch) | |
tree | f67503164f017b45ab425827d71fb7d23920a519 /Documentation/DocBook/kernel-api.tmpl | |
parent | c39736823232bc3ca113c8228fa852c09fba300e (diff) | |
parent | 0a85e9a271a754e352af8a8b625025017fd97449 (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/kernel-api.tmpl')
-rw-r--r-- | Documentation/DocBook/kernel-api.tmpl | 55 |
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> |