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Diffstat (limited to 'kernel/Documentation/hwmon/pc87427')
| -rw-r--r-- | kernel/Documentation/hwmon/pc87427 | 59 |
1 files changed, 59 insertions, 0 deletions
diff --git a/kernel/Documentation/hwmon/pc87427 b/kernel/Documentation/hwmon/pc87427 new file mode 100644 index 000000000..c313eb66e --- /dev/null +++ b/kernel/Documentation/hwmon/pc87427 @@ -0,0 +1,59 @@ +Kernel driver pc87427 +===================== + +Supported chips: + * National Semiconductor PC87427 + Prefix: 'pc87427' + Addresses scanned: none, address read from Super I/O config space + Datasheet: No longer available + +Author: Jean Delvare <jdelvare@suse.de> + +Thanks to Amir Habibi at Candelis for setting up a test system, and to +Michael Kress for testing several iterations of this driver. + + +Description +----------- + +The National Semiconductor Super I/O chip includes complete hardware +monitoring capabilities. It can monitor up to 18 voltages, 8 fans and +6 temperature sensors. Only the fans and temperatures are supported at +the moment, voltages aren't. + +This chip also has fan controlling features (up to 4 PWM outputs), +which are partly supported by this driver. + +The driver assumes that no more than one chip is present, which seems +reasonable. + + +Fan Monitoring +-------------- + +Fan rotation speeds are reported as 14-bit values from a gated clock +signal. Speeds down to 83 RPM can be measured. + +An alarm is triggered if the rotation speed drops below a programmable +limit. Another alarm is triggered if the speed is too low to be measured +(including stalled or missing fan). + + +Fan Speed Control +----------------- + +Fan speed can be controlled by PWM outputs. There are 4 possible modes: +always off, always on, manual and automatic. The latter isn't supported +by the driver: you can only return to that mode if it was the original +setting, and the configuration interface is missing. + + +Temperature Monitoring +---------------------- + +The PC87427 relies on external sensors (following the SensorPath +standard), so the resolution and range depend on the type of sensor +connected. The integer part can be 8-bit or 9-bit, and can be signed or +not. I couldn't find a way to figure out the external sensor data +temperature format, so user-space adjustment (typically by a factor 2) +may be required. |