summary

优龙Intel Xscale PXA270 开发平台 LINUX源码, 包括 平台用户手册, PDF原理图, kernel, driver代码. 非常有参考价值.

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)