| Kernel driver lm87 |
| ================== |
| |
| Supported chips: |
| * National Semiconductor LM87 |
| Prefix: 'lm87' |
| Addresses scanned: I2C 0x2c - 0x2e |
| Datasheet: http://www.national.com/pf/LM/LM87.html |
| * Analog Devices ADM1024 |
| Prefix: 'adm1024' |
| Addresses scanned: I2C 0x2c - 0x2e |
| Datasheet: http://www.analog.com/en/prod/0,2877,ADM1024,00.html |
| |
| Authors: |
| Frodo Looijaard <frodol@dds.nl>, |
| Philip Edelbrock <phil@netroedge.com>, |
| Mark Studebaker <mdsxyz123@yahoo.com>, |
| Stephen Rousset <stephen.rousset@rocketlogix.com>, |
| Dan Eaton <dan.eaton@rocketlogix.com>, |
| Jean Delvare <khali@linux-fr.org>, |
| Original 2.6 port Jeff Oliver |
| |
| Description |
| ----------- |
| |
| This driver implements support for the National Semiconductor LM87 |
| and the Analog Devices ADM1024. |
| |
| The LM87 implements up to three temperature sensors, up to two fan |
| rotation speed sensors, up to seven voltage sensors, alarms, and some |
| miscellaneous stuff. The ADM1024 is fully compatible. |
| |
| Temperatures are measured in degrees Celsius. Each input has a high |
| and low alarm settings. A high limit produces an alarm when the value |
| goes above it, and an alarm is also produced when the value goes below |
| the low limit. |
| |
| Fan rotation speeds are reported in RPM (rotations per minute). An alarm is |
| triggered if the rotation speed has dropped below a programmable limit. Fan |
| readings can be divided by a programmable divider (1, 2, 4 or 8) to give |
| the readings more range or accuracy. Not all RPM values can accurately be |
| represented, so some rounding is done. With a divider of 2, the lowest |
| representable value is around 2600 RPM. |
| |
| Voltage sensors (also known as IN sensors) report their values in |
| volts. An alarm is triggered if the voltage has crossed a programmable |
| minimum or maximum limit. Note that minimum in this case always means |
| 'closest to zero'; this is important for negative voltage measurements. |
| |
| If an alarm triggers, it will remain triggered until the hardware register |
| is read at least once. This means that the cause for the alarm may |
| already have disappeared! Note that in the current implementation, all |
| hardware registers are read whenever any data is read (unless it is less |
| than 1.0 seconds since the last update). This means that you can easily |
| miss once-only alarms. |
| |
| The lm87 driver only updates its values each 1.0 seconds; reading it more |
| often will do no harm, but will return 'old' values. |
| |
| |
| Hardware Configurations |
| ----------------------- |
| |
| The LM87 has four pins which can serve one of two possible functions, |
| depending on the hardware configuration. |
| |
| Some functions share pins, so not all functions are available at the same |
| time. Which are depends on the hardware setup. This driver normally |
| assumes that firmware configured the chip correctly. Where this is not |
| the case, platform code must set the I2C client's platform_data to point |
| to a u8 value to be written to the channel register. |
| |
| For reference, here is the list of exclusive functions: |
| - in0+in5 (default) or temp3 |
| - fan1 (default) or in6 |
| - fan2 (default) or in7 |
| - VID lines (default) or IRQ lines (not handled by this driver) |