lm87.rst (3109B)
1Kernel driver lm87 2================== 3 4Supported chips: 5 6 * National Semiconductor LM87 7 8 Prefix: 'lm87' 9 10 Addresses scanned: I2C 0x2c - 0x2e 11 12 Datasheet: http://www.national.com/pf/LM/LM87.html 13 14 * Analog Devices ADM1024 15 16 Prefix: 'adm1024' 17 18 Addresses scanned: I2C 0x2c - 0x2e 19 20 Datasheet: https://www.analog.com/en/prod/0,2877,ADM1024,00.html 21 22 23Authors: 24 - Frodo Looijaard <frodol@dds.nl>, 25 - Philip Edelbrock <phil@netroedge.com>, 26 - Mark Studebaker <mdsxyz123@yahoo.com>, 27 - Stephen Rousset <stephen.rousset@rocketlogix.com>, 28 - Dan Eaton <dan.eaton@rocketlogix.com>, 29 - Jean Delvare <jdelvare@suse.de>, 30 - Original 2.6 port Jeff Oliver 31 32Description 33----------- 34 35This driver implements support for the National Semiconductor LM87 36and the Analog Devices ADM1024. 37 38The LM87 implements up to three temperature sensors, up to two fan 39rotation speed sensors, up to seven voltage sensors, alarms, and some 40miscellaneous stuff. The ADM1024 is fully compatible. 41 42Temperatures are measured in degrees Celsius. Each input has a high 43and low alarm settings. A high limit produces an alarm when the value 44goes above it, and an alarm is also produced when the value goes below 45the low limit. 46 47Fan rotation speeds are reported in RPM (rotations per minute). An alarm is 48triggered if the rotation speed has dropped below a programmable limit. Fan 49readings can be divided by a programmable divider (1, 2, 4 or 8) to give 50the readings more range or accuracy. Not all RPM values can accurately be 51represented, so some rounding is done. With a divider of 2, the lowest 52representable value is around 2600 RPM. 53 54Voltage sensors (also known as IN sensors) report their values in 55volts. An alarm is triggered if the voltage has crossed a programmable 56minimum or maximum limit. Note that minimum in this case always means 57'closest to zero'; this is important for negative voltage measurements. 58 59If an alarm triggers, it will remain triggered until the hardware register 60is read at least once. This means that the cause for the alarm may 61already have disappeared! Note that in the current implementation, all 62hardware registers are read whenever any data is read (unless it is less 63than 1.0 seconds since the last update). This means that you can easily 64miss once-only alarms. 65 66The lm87 driver only updates its values each 1.0 seconds; reading it more 67often will do no harm, but will return 'old' values. 68 69 70Hardware Configurations 71----------------------- 72 73The LM87 has four pins which can serve one of two possible functions, 74depending on the hardware configuration. 75 76Some functions share pins, so not all functions are available at the same 77time. Which are depends on the hardware setup. This driver normally 78assumes that firmware configured the chip correctly. Where this is not 79the case, platform code must set the I2C client's platform_data to point 80to a u8 value to be written to the channel register. 81 82For reference, here is the list of exclusive functions: 83 - in0+in5 (default) or temp3 84 - fan1 (default) or in6 85 - fan2 (default) or in7 86 - VID lines (default) or IRQ lines (not handled by this driver)