linux/Documentation/laptops
Henrique de Moraes Holschuh d73772474f 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>
2009-06-18 01:30:57 -04:00
..
00-INDEX laptops: move laptop-mode.txt to Documentation/laptops/ 2008-03-12 02:37:21 -04:00
acer-wmi.txt acer-wmi: Update copyright notice & documentation 2009-04-04 12:36:31 -04:00
disk-shock-protection.txt ata: Add documentation for hard disk shock protection interface (v3) 2008-10-13 21:39:50 +02:00
laptop-mode.txt laptops: move laptop-mode.txt to Documentation/laptops/ 2008-03-12 02:37:21 -04:00
sony-laptop.txt sony-laptop - Move sony-laptop.txt to Documentation/laptops 2008-02-09 04:15:40 -05:00
sonypi.txt sonypi - Move sonypi.txt to Documentation/laptops 2008-02-09 04:15:53 -05:00
thinkpad-acpi.txt thinkpad-acpi: support the second fan on the X61 2009-06-18 01:30:57 -04:00