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1Kernel driver pc874272=====================3 4Supported chips:5 6 * National Semiconductor PC874277 8 Prefix: 'pc87427'9 10 Addresses scanned: none, address read from Super I/O config space11 12 Datasheet: No longer available13 14Author: Jean Delvare <jdelvare@suse.de>15 16Thanks to Amir Habibi at Candelis for setting up a test system, and to17Michael Kress for testing several iterations of this driver.18 19 20Description21-----------22 23The National Semiconductor Super I/O chip includes complete hardware24monitoring capabilities. It can monitor up to 18 voltages, 8 fans and256 temperature sensors. Only the fans and temperatures are supported at26the moment, voltages aren't.27 28This chip also has fan controlling features (up to 4 PWM outputs),29which are partly supported by this driver.30 31The driver assumes that no more than one chip is present, which seems32reasonable.33 34 35Fan Monitoring36--------------37 38Fan rotation speeds are reported as 14-bit values from a gated clock39signal. Speeds down to 83 RPM can be measured.40 41An alarm is triggered if the rotation speed drops below a programmable42limit. Another alarm is triggered if the speed is too low to be measured43(including stalled or missing fan).44 45 46Fan Speed Control47-----------------48 49Fan speed can be controlled by PWM outputs. There are 4 possible modes:50always off, always on, manual and automatic. The latter isn't supported51by the driver: you can only return to that mode if it was the original52setting, and the configuration interface is missing.53 54 55Temperature Monitoring56----------------------57 58The PC87427 relies on external sensors (following the SensorPath59standard), so the resolution and range depend on the type of sensor60connected. The integer part can be 8-bit or 9-bit, and can be signed or61not. I couldn't find a way to figure out the external sensor data62temperature format, so user-space adjustment (typically by a factor 2)63may be required.64