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linux-sg2042/Documentation/i2c/summary

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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!
2005-04-17 06:20:36 +08:00
I2C and SMBus
=============
I2C (pronounce: I squared C) is a protocol developed by Philips. It is a
i2c: i2c probe() and remove() documented Update Documentation/i2c to match previous patches updating probe() and remove() logic. Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Signed-off-by: Jean Delvare <khali@linux-fr.org>
2007-05-02 05:26:31 +08:00
slow two-wire protocol (variable speed, up to 400 kHz), with a high speed
extension (3.4 MHz). It provides an inexpensive bus for connecting many
types of devices with infrequent or low bandwidth communications needs.
I2C is widely used with embedded systems. Some systems use variants that
don't meet branding requirements, and so are not advertised as being I2C.
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!
2005-04-17 06:20:36 +08:00
i2c: i2c probe() and remove() documented Update Documentation/i2c to match previous patches updating probe() and remove() logic. Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Signed-off-by: Jean Delvare <khali@linux-fr.org>
2007-05-02 05:26:31 +08:00
SMBus (System Management Bus) is based on the I2C protocol, and is mostly
a subset of I2C protocols and signaling. Many I2C devices will work on an
SMBus, but some SMBus protocols add semantics beyond what is required to
achieve I2C branding. Modern PC mainboards rely on SMBus. The most common
devices connected through SMBus are RAM modules configured using I2C EEPROMs,
and hardware monitoring chips.
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!
2005-04-17 06:20:36 +08:00
i2c: i2c probe() and remove() documented Update Documentation/i2c to match previous patches updating probe() and remove() logic. Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Signed-off-by: Jean Delvare <khali@linux-fr.org>
2007-05-02 05:26:31 +08:00
Because the SMBus is mostly a subset of the generalized I2C bus, we can
use its protocols on many I2C systems. However, there are systems that don't
meet both SMBus and I2C electrical constraints; and others which can't
implement all the common SMBus protocol semantics or messages.
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!
2005-04-17 06:20:36 +08:00
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
i2c: Delete an outdated piece of documentation I'm amazed that this old piece of documentation managed to survive until today. Signed-off-by: Jean Delvare <khali@linux-fr.org>
2007-12-12 20:45:24 +08:00
of I2C adapters. Each specific adapter driver either depends on one algorithm
driver, or includes its own implementation.
i2c: i2c probe() and remove() documented Update Documentation/i2c to match previous patches updating probe() and remove() logic. Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Signed-off-by: Jean Delvare <khali@linux-fr.org>
2007-05-02 05:26:31 +08:00
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!
2005-04-17 06:20:36 +08:00
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.
i2c: Delete an outdated piece of documentation I'm amazed that this old piece of documentation managed to survive until today. Signed-off-by: Jean Delvare <khali@linux-fr.org>
2007-12-12 20:45:24 +08:00
For a given configuration, you will need a driver for your I2C bus, and
drivers for your I2C devices (usually one driver for each device).
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!
2005-04-17 06:20:36 +08:00
i2c: i2c probe() and remove() documented Update Documentation/i2c to match previous patches updating probe() and remove() logic. Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Signed-off-by: Jean Delvare <khali@linux-fr.org>
2007-05-02 05:26:31 +08:00
At this time, Linux only operates I2C (or SMBus) in master mode; you can't
use these APIs to make a Linux system behave as a slave/device, either to
speak a custom protocol or to emulate some other device.