tree 13d767bb08fe98ee73a278f44c8f3d79a63cc68b
parent 26de89b77388a0ae034eccca37464a20eb541640
author Josh Lehan <krellan@google.com> 1601578149 -0700
committer Jason Ling <jasonling@google.com> 1645049389 +0000

pid/zone: Restore PWM when fans returned to auto

This makes use of the improved write() interface, to allow the
PID-loop-determined PWM to be restored, when the fan is returned to
automatic mode.

Without this fix, a fan set to manual mode, then manually set to a
different speed, would not properly return to the correct speed, when
transitioning back to automatic from manual.

This patch also adds a stub to allow the caller to learn the raw PWM
value written as output, another useful write() interface improvement.
Although not the topic of this change, it is included here, to avoid
later patch conflicts.

Tested: I can now correctly toggle between automatic, and manual, fan
control. Upon resuming automatic control, after a few seconds, the fan
PWM is now properly restored, to what the PID loop wanted it to be at.

Signed-off-by: Josh Lehan <krellan@google.com>
Signed-off-by: Jason Ling <jasonling@google.com>
Change-Id: I46fc65d6b931755d51093ea475c64cf5e3e6bacb