tree 7564212618d43910de01a818c0cdef5759ad12a9
parent d7880f10c5d42ba182a97c1fd41d41d0b8837097
author Henrique de Moraes Holschuh <hmh@hmh.eng.br> 1245296417 -0300
committer Len Brown <len.brown@intel.com> 1245303057 -0400

thinkpad-acpi: support the second fan on the X61

Support reading the tachometer of the auxiliary fan of a X60/X61.

It was found out by sheer luck, that bit 0 of EC register 0x31
(formely HBRV) selects which fan is active for tachometer readings
through EC 0x84/0x085: 0 for fan1, 1 for fan2.

Many thanks to Christoph Kl??nter, to Whoopie, and to weasel, who
helped confirm that behaviour.

Fan control through EC HFSP applies to both fans equally, regardless
of the state of bit 0 of EC 0x31.  That matches the way the DSDT uses
HFSP.

In order to better support the secondary fan, export a second
tachometer over hwmon, and add defensive measures to make sure we are
reading the correct tachometer.

Support for the second fan is whitelist-based, as I have not found
anything obvious to look for in the DSDT to detect the presence of
the second fan.

Signed-off-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
Signed-off-by: Len Brown <len.brown@intel.com>