1da177e4c3
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!
75 lines
2.8 KiB
Text
75 lines
2.8 KiB
Text
This is an explanation of what i2c is, and what is supported in this package.
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I2C and SMBus
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=============
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I2C (pronounce: I squared C) is a protocol developed by Philips. It is a
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slow two-wire protocol (10-400 kHz), but it suffices for many types of
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devices.
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SMBus (System Management Bus) is a subset of the I2C protocol. Many
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modern mainboards have a System Management Bus. There are a lot of
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devices which can be connected to a SMBus; the most notable are modern
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memory chips with EEPROM memories and chips for hardware monitoring.
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Because the SMBus is just a special case of the generalized I2C bus, we
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can simulate the SMBus protocol on plain I2C busses. The reverse is
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regretfully impossible.
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Terminology
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===========
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When we talk about I2C, we use the following terms:
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Bus -> Algorithm
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Adapter
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Device -> Driver
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Client
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An Algorithm driver contains general code that can be used for a whole class
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of I2C adapters. Each specific adapter driver depends on one algorithm
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driver.
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A Driver driver (yes, this sounds ridiculous, sorry) contains the general
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code to access some type of device. Each detected device gets its own
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data in the Client structure. Usually, Driver and Client are more closely
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integrated than Algorithm and Adapter.
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For a given configuration, you will need a driver for your I2C bus (usually
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a separate Adapter and Algorithm driver), and drivers for your I2C devices
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(usually one driver for each device). There are no I2C device drivers
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in this package. See the lm_sensors project http://www.lm-sensors.nu
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for device drivers.
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Included Bus Drivers
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====================
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Note that only stable drivers are patched into the kernel by 'mkpatch'.
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Base modules
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------------
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i2c-core: The basic I2C code, including the /proc/bus/i2c* interface
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i2c-dev: The /dev/i2c-* interface
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i2c-proc: The /proc/sys/dev/sensors interface for device (client) drivers
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Algorithm drivers
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-----------------
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i2c-algo-8xx: An algorithm for CPM's I2C device in Motorola 8xx processors (NOT BUILT BY DEFAULT)
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i2c-algo-bit: A bit-banging algorithm
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i2c-algo-pcf: A PCF 8584 style algorithm
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i2c-algo-ibm_ocp: An algorithm for the I2C device in IBM 4xx processors (NOT BUILT BY DEFAULT)
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Adapter drivers
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---------------
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i2c-elektor: Elektor ISA card (uses i2c-algo-pcf)
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i2c-elv: ELV parallel port adapter (uses i2c-algo-bit)
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i2c-pcf-epp: PCF8584 on a EPP parallel port (uses i2c-algo-pcf) (NOT mkpatched)
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i2c-philips-par: Philips style parallel port adapter (uses i2c-algo-bit)
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i2c-adap-ibm_ocp: IBM 4xx processor I2C device (uses i2c-algo-ibm_ocp) (NOT BUILT BY DEFAULT)
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i2c-pport: Primitive parallel port adapter (uses i2c-algo-bit)
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i2c-rpx: RPX board Motorola 8xx I2C device (uses i2c-algo-8xx) (NOT BUILT BY DEFAULT)
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i2c-velleman: Velleman K8000 parallel port adapter (uses i2c-algo-bit)
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