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authorLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-17 02:20:36 +0400
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-17 02:20:36 +0400
commit1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch)
tree0bba044c4ce775e45a88a51686b5d9f90697ea9d /Documentation/i2c/summary
downloadlinux-1da177e4c3f41524e886b7f1b8a0c1fc7321cac2.tar.xz
Linux-2.6.12-rc2
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
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+This is an explanation of what i2c is, and what is supported in this package.
+
+I2C and SMBus
+=============
+
+I2C (pronounce: I squared C) is a protocol developed by Philips. It is a
+slow two-wire protocol (10-400 kHz), but it suffices for many types of
+devices.
+
+SMBus (System Management Bus) is a subset of the I2C protocol. Many
+modern mainboards have a System Management Bus. There are a lot of
+devices which can be connected to a SMBus; the most notable are modern
+memory chips with EEPROM memories and chips for hardware monitoring.
+
+Because the SMBus is just a special case of the generalized I2C bus, we
+can simulate the SMBus protocol on plain I2C busses. The reverse is
+regretfully impossible.
+
+
+Terminology
+===========
+
+When we talk about I2C, we use the following terms:
+ Bus -> Algorithm
+ Adapter
+ Device -> Driver
+ Client
+
+An Algorithm driver contains general code that can be used for a whole class
+of I2C adapters. Each specific adapter driver depends on one algorithm
+driver.
+A Driver driver (yes, this sounds ridiculous, sorry) contains the general
+code to access some type of device. Each detected device gets its own
+data in the Client structure. Usually, Driver and Client are more closely
+integrated than Algorithm and Adapter.
+
+For a given configuration, you will need a driver for your I2C bus (usually
+a separate Adapter and Algorithm driver), and drivers for your I2C devices
+(usually one driver for each device). There are no I2C device drivers
+in this package. See the lm_sensors project http://www.lm-sensors.nu
+for device drivers.
+
+
+Included Bus Drivers
+====================
+Note that only stable drivers are patched into the kernel by 'mkpatch'.
+
+
+Base modules
+------------
+
+i2c-core: The basic I2C code, including the /proc/bus/i2c* interface
+i2c-dev: The /dev/i2c-* interface
+i2c-proc: The /proc/sys/dev/sensors interface for device (client) drivers
+
+Algorithm drivers
+-----------------
+
+i2c-algo-8xx: An algorithm for CPM's I2C device in Motorola 8xx processors (NOT BUILT BY DEFAULT)
+i2c-algo-bit: A bit-banging algorithm
+i2c-algo-pcf: A PCF 8584 style algorithm
+i2c-algo-ibm_ocp: An algorithm for the I2C device in IBM 4xx processors (NOT BUILT BY DEFAULT)
+
+Adapter drivers
+---------------
+
+i2c-elektor: Elektor ISA card (uses i2c-algo-pcf)
+i2c-elv: ELV parallel port adapter (uses i2c-algo-bit)
+i2c-pcf-epp: PCF8584 on a EPP parallel port (uses i2c-algo-pcf) (NOT mkpatched)
+i2c-philips-par: Philips style parallel port adapter (uses i2c-algo-bit)
+i2c-adap-ibm_ocp: IBM 4xx processor I2C device (uses i2c-algo-ibm_ocp) (NOT BUILT BY DEFAULT)
+i2c-pport: Primitive parallel port adapter (uses i2c-algo-bit)
+i2c-rpx: RPX board Motorola 8xx I2C device (uses i2c-algo-8xx) (NOT BUILT BY DEFAULT)
+i2c-velleman: Velleman K8000 parallel port adapter (uses i2c-algo-bit)
+