projects / deliverable / linux.git / blame
| Commit | Line | Data |
|---|---|---|
| 7f15b664 M |
1 | Kernel driver lm87 |
| 2 | ================== | |
| 3 | ||
| 4 | Supported chips: | |
| 5 | * National Semiconductor LM87 | |
| 6 | Prefix: 'lm87' | |
| c7fa3737 | 7 | Addresses scanned: I2C 0x2c - 0x2e |
| 7f15b664 | 8 | Datasheet: http://www.national.com/pf/LM/LM87.html |
| c7fa3737 JD |
9 | * Analog Devices ADM1024 |
| 10 | Prefix: 'adm1024' | |
| 11 | Addresses scanned: I2C 0x2c - 0x2e | |
| 12 | Datasheet: http://www.analog.com/en/prod/0,2877,ADM1024,00.html | |
| 7f15b664 M |
13 | |
| 14 | Authors: | |
| 15 | Frodo Looijaard <frodol@dds.nl>, | |
| 16 | Philip Edelbrock <phil@netroedge.com>, | |
| 17 | Mark Studebaker <mdsxyz123@yahoo.com>, | |
| 18 | Stephen Rousset <stephen.rousset@rocketlogix.com>, | |
| 19 | Dan Eaton <dan.eaton@rocketlogix.com>, | |
| 20 | Jean Delvare <khali@linux-fr.org>, | |
| 21 | Original 2.6 port Jeff Oliver | |
| 22 | ||
| 23 | Description | |
| 24 | ----------- | |
| 25 | ||
| c7fa3737 JD |
26 | This driver implements support for the National Semiconductor LM87 |
| 27 | and the Analog Devices ADM1024. | |
| 7f15b664 M |
28 | |
| 29 | The LM87 implements up to three temperature sensors, up to two fan | |
| 30 | rotation speed sensors, up to seven voltage sensors, alarms, and some | |
| c7fa3737 | 31 | miscellaneous stuff. The ADM1024 is fully compatible. |
| 7f15b664 M |
32 | |
| 33 | Temperatures are measured in degrees Celsius. Each input has a high | |
| 34 | and low alarm settings. A high limit produces an alarm when the value | |
| 35 | goes above it, and an alarm is also produced when the value goes below | |
| 36 | the low limit. | |
| 37 | ||
| 38 | Fan rotation speeds are reported in RPM (rotations per minute). An alarm is | |
| 39 | triggered if the rotation speed has dropped below a programmable limit. Fan | |
| 40 | readings can be divided by a programmable divider (1, 2, 4 or 8) to give | |
| 41 | the readings more range or accuracy. Not all RPM values can accurately be | |
| 42 | represented, so some rounding is done. With a divider of 2, the lowest | |
| 43 | representable value is around 2600 RPM. | |
| 44 | ||
| 45 | Voltage sensors (also known as IN sensors) report their values in | |
| 46 | volts. An alarm is triggered if the voltage has crossed a programmable | |
| 47 | minimum or maximum limit. Note that minimum in this case always means | |
| 48 | 'closest to zero'; this is important for negative voltage measurements. | |
| 49 | ||
| 50 | If an alarm triggers, it will remain triggered until the hardware register | |
| 51 | is read at least once. This means that the cause for the alarm may | |
| 52 | already have disappeared! Note that in the current implementation, all | |
| 53 | hardware registers are read whenever any data is read (unless it is less | |
| 54 | than 1.0 seconds since the last update). This means that you can easily | |
| 55 | miss once-only alarms. | |
| 56 | ||
| 57 | The lm87 driver only updates its values each 1.0 seconds; reading it more | |
| 58 | often will do no harm, but will return 'old' values. | |
| 59 | ||
| 60 | ||
| 61 | Hardware Configurations | |
| 62 | ----------------------- | |
| 63 | ||
| 64 | The LM87 has four pins which can serve one of two possible functions, | |
| 65 | depending on the hardware configuration. | |
| 66 | ||
| 67 | Some functions share pins, so not all functions are available at the same | |
| 68 | time. Which are depends on the hardware setup. This driver assumes that | |
| 69 | the BIOS configured the chip correctly. In that respect, it differs from | |
| 70 | the original driver (from lm_sensors for Linux 2.4), which would force the | |
| 71 | LM87 to an arbitrary, compile-time chosen mode, regardless of the actual | |
| 72 | chipset wiring. | |
| 73 | ||
| 74 | For reference, here is the list of exclusive functions: | |
| 75 | - in0+in5 (default) or temp3 | |
| 76 | - fan1 (default) or in6 | |
| 77 | - fan2 (default) or in7 | |
| 78 | - VID lines (default) or IRQ lines (not handled by this driver) |