[patch] enhance powerd(8) to handle max temperature

[Pietro Cerutti]

Hi list,
here is a patch to allow powerd(8) accept a "-t tval" option to set a
temperature limit above which performance should be decreased.
It's a first draft, and I identified the following problems:

- the CPU temperature takes some time to decrease, so powerd keeps
decreasing the CPU frequency until the temperature is below the limit.
The effect is a "increase to maximum, decrease to minimum, increase to
maximum, decrease to minimum, ...." which may not be desirable.

- the temperature is retrieved by the hw.acpi.thermal.tz0.temperature
sysctl MIB. Support for other methods would be desirable.

The patches to powerd.c and powerd.8 are here:
http://www.gahr.ch/FreeBSD/patches/powerd.c.diff
http://www.gahr.ch/FreeBSD/patches/powerd.8.diff

Any comment is welcome!

-- 
Pietro Cerutti

PGP Public Key:
http://gahr.ch/pgp