| Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1 | This is an explanation of what i2c is, and what is supported in this package. |
| 2 | |
| 3 | I2C and SMBus |
| 4 | ============= |
| 5 | |
| 6 | I2C (pronounce: I squared C) is a protocol developed by Philips. It is a |
| 7 | slow two-wire protocol (10-400 kHz), but it suffices for many types of |
| 8 | devices. |
| 9 | |
| 10 | SMBus (System Management Bus) is a subset of the I2C protocol. Many |
| 11 | modern mainboards have a System Management Bus. There are a lot of |
| 12 | devices which can be connected to a SMBus; the most notable are modern |
| 13 | memory chips with EEPROM memories and chips for hardware monitoring. |
| 14 | |
| 15 | Because the SMBus is just a special case of the generalized I2C bus, we |
| 16 | can simulate the SMBus protocol on plain I2C busses. The reverse is |
| 17 | regretfully impossible. |
| 18 | |
| 19 | |
| 20 | Terminology |
| 21 | =========== |
| 22 | |
| 23 | When we talk about I2C, we use the following terms: |
| 24 | Bus -> Algorithm |
| 25 | Adapter |
| 26 | Device -> Driver |
| 27 | Client |
| 28 | |
| 29 | An Algorithm driver contains general code that can be used for a whole class |
| 30 | of I2C adapters. Each specific adapter driver depends on one algorithm |
| 31 | driver. |
| 32 | A Driver driver (yes, this sounds ridiculous, sorry) contains the general |
| 33 | code to access some type of device. Each detected device gets its own |
| 34 | data in the Client structure. Usually, Driver and Client are more closely |
| 35 | integrated than Algorithm and Adapter. |
| 36 | |
| 37 | For a given configuration, you will need a driver for your I2C bus (usually |
| 38 | a separate Adapter and Algorithm driver), and drivers for your I2C devices |
| 39 | (usually one driver for each device). There are no I2C device drivers |
| 40 | in this package. See the lm_sensors project http://www.lm-sensors.nu |
| 41 | for device drivers. |
| 42 | |
| 43 | |
| 44 | Included Bus Drivers |
| 45 | ==================== |
| 46 | Note that only stable drivers are patched into the kernel by 'mkpatch'. |
| 47 | |
| 48 | |
| 49 | Base modules |
| 50 | ------------ |
| 51 | |
| 52 | i2c-core: The basic I2C code, including the /proc/bus/i2c* interface |
| 53 | i2c-dev: The /dev/i2c-* interface |
| 54 | i2c-proc: The /proc/sys/dev/sensors interface for device (client) drivers |
| 55 | |
| 56 | Algorithm drivers |
| 57 | ----------------- |
| 58 | |
| 59 | i2c-algo-8xx: An algorithm for CPM's I2C device in Motorola 8xx processors (NOT BUILT BY DEFAULT) |
| 60 | i2c-algo-bit: A bit-banging algorithm |
| 61 | i2c-algo-pcf: A PCF 8584 style algorithm |
| 62 | i2c-algo-ibm_ocp: An algorithm for the I2C device in IBM 4xx processors (NOT BUILT BY DEFAULT) |
| 63 | |
| 64 | Adapter drivers |
| 65 | --------------- |
| 66 | |
| 67 | i2c-elektor: Elektor ISA card (uses i2c-algo-pcf) |
| 68 | i2c-elv: ELV parallel port adapter (uses i2c-algo-bit) |
| 69 | i2c-pcf-epp: PCF8584 on a EPP parallel port (uses i2c-algo-pcf) (NOT mkpatched) |
| 70 | i2c-philips-par: Philips style parallel port adapter (uses i2c-algo-bit) |
| 71 | i2c-adap-ibm_ocp: IBM 4xx processor I2C device (uses i2c-algo-ibm_ocp) (NOT BUILT BY DEFAULT) |
| 72 | i2c-pport: Primitive parallel port adapter (uses i2c-algo-bit) |
| 73 | i2c-rpx: RPX board Motorola 8xx I2C device (uses i2c-algo-8xx) (NOT BUILT BY DEFAULT) |
| 74 | i2c-velleman: Velleman K8000 parallel port adapter (uses i2c-algo-bit) |
| 75 | |