76 lines
2.8 KiB
Text
76 lines
2.8 KiB
Text
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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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