[ltp] Re: thinkpad-acpi: fancontrol

[Henrique de Moraes Holschuh]

On Mon, 23 Jul 2007, Peter Jordan wrote:
> Ok, but is there an better way to change from disengaged mode to a
> normal level then this:
> 
> change to disengaged mode:
> echo 0 > /sys/bus/platform/devices/thinkpad_acpi/pwm1_enable
> 
> change to "normal" level:
> echo 1 > /sys/bus/platform/devices/thinkpad_acpi/pwm1_enable
> echo [0-255] > /sys/bus/platform/devices/thinkpad_acpi/pwm1

There is also the EC "auto" level, using
echo 2 > /sys/bus/platform/devices/thinkpad_acpi/pwm1_enable

And that's exactly how it is supposed to work.  But you don't need to keep
setting pwm1, it should remember the value you last wrote there.  It will
auto-update if it is in pwm1_enable mode 1 (manual) and anything changes the
fan level, though (e.g. ACPI DSDT, or thinkpad-acpi procfs).

So, to "confuse" the EC and avoid its calibration loop, you just set pwm1 to
the desired level, and keep setting pwm1_enable to 0 and 1 as needed.

> It seems that the command "echo [0-255] >
> /sys/bus/platform/devices/thinkpad_acpi/pwm1" does not work by itself.

It won't change the pwm controller mode, so it *does* work by itself, but
only if the pwm controller is already in manual mode (pwm1_enable == 1).

-- 
  "One disk to rule them all, One disk to find them. One disk to bring
  them all and in the darkness grind them. In the Land of Redmond
  where the shadows lie." -- The Silicon Valley Tarot
  Henrique Holschuh