This is an explanation of what i2c is, and what is supported.

I2C and SMBus
=============

I2C (pronounce: I square C) is a protocol developed by Philips. It is a 
slow two-wire protocol (10-100 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).


Included Drivers
================

Base modules
------------

i2c-core: The basic I2C code, including the /proc interface
i2c-dev:  The /dev interface

Algorithm drivers
-----------------

i2c-algo-bit: A bit-banging algorithm
i2c-algo-pcf: A PCF 8584 style algorithm

Adapter drivers
---------------

i2c-elektor:     Elektor ISA card (uses i2c-algo-pcf)
i2c-elv:         ELV parallel port adapter (uses i2c-algo-bit)
i2c-philips-par: Philips style parallel port adapter (uses i2c-algo-bit)
i2c-velleman:    Velleman K9000 parallel port adapter (uses i2c-algo-bit)