Kernel driver pc87427
=====================

Supported chips:
  * National Semiconductor PC87427
    Prefix: 'pc87427'
    Addresses scanned: none, address read from Super I/O config space
    Datasheet: http://www.winbond.com.tw/E-WINBONDHTM/partner/apc_007.html

Author: Jean Delvare <khali@linux-fr.org>

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 are supported at the moment.

This chip also has fan controlling features, which are not yet supported
by this driver either.

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 to be measured
(including stalled or missing fan).