1Kernel driver lm87 2================== 3 4Supported chips: 5 * National Semiconductor LM87 6 Prefix: 'lm87' 7 Addresses scanned: I2C 0x2c - 0x2f 8 Datasheet: http://www.national.com/pf/LM/LM87.html 9 10Authors: 11 Frodo Looijaard <frodol@dds.nl>, 12 Philip Edelbrock <phil@netroedge.com>, 13 Mark Studebaker <mdsxyz123@yahoo.com>, 14 Stephen Rousset <stephen.rousset@rocketlogix.com>, 15 Dan Eaton <dan.eaton@rocketlogix.com>, 16 Jean Delvare <khali@linux-fr.org>, 17 Original 2.6 port Jeff Oliver 18 19Description 20----------- 21 22This driver implements support for the National Semiconductor LM87. 23 24The LM87 implements up to three temperature sensors, up to two fan 25rotation speed sensors, up to seven voltage sensors, alarms, and some 26miscellaneous stuff. 27 28Temperatures are measured in degrees Celsius. Each input has a high 29and low alarm settings. A high limit produces an alarm when the value 30goes above it, and an alarm is also produced when the value goes below 31the low limit. 32 33Fan rotation speeds are reported in RPM (rotations per minute). An alarm is 34triggered if the rotation speed has dropped below a programmable limit. Fan 35readings can be divided by a programmable divider (1, 2, 4 or 8) to give 36the readings more range or accuracy. Not all RPM values can accurately be 37represented, so some rounding is done. With a divider of 2, the lowest 38representable value is around 2600 RPM. 39 40Voltage sensors (also known as IN sensors) report their values in 41volts. An alarm is triggered if the voltage has crossed a programmable 42minimum or maximum limit. Note that minimum in this case always means 43'closest to zero'; this is important for negative voltage measurements. 44 45If an alarm triggers, it will remain triggered until the hardware register 46is read at least once. This means that the cause for the alarm may 47already have disappeared! Note that in the current implementation, all 48hardware registers are read whenever any data is read (unless it is less 49than 1.0 seconds since the last update). This means that you can easily 50miss once-only alarms. 51 52The lm87 driver only updates its values each 1.0 seconds; reading it more 53often will do no harm, but will return 'old' values. 54 55 56Hardware Configurations 57----------------------- 58 59The LM87 has four pins which can serve one of two possible functions, 60depending on the hardware configuration. 61 62Some functions share pins, so not all functions are available at the same 63time. Which are depends on the hardware setup. This driver assumes that 64the BIOS configured the chip correctly. In that respect, it differs from 65the original driver (from lm_sensors for Linux 2.4), which would force the 66LM87 to an arbitrary, compile-time chosen mode, regardless of the actual 67chipset wiring. 68 69For reference, here is the list of exclusive functions: 70 - in0+in5 (default) or temp3 71 - fan1 (default) or in6 72 - fan2 (default) or in7 73 - VID lines (default) or IRQ lines (not handled by this driver) 74