lm_sensors fancontrol and ASUS quiet fan BIOS

I have an ASUS K8V SE Deluxe board. I used to run a stock 2.6.13.2
kernel and have now switched to a stock 2.6.19.2 (I have also switched
from Gentoo to Debian, but I doubt that is the issue). I used to have
the Quiet Fan BIOS option enabled, but also used the fancontrol script
that now comes with lm_sensors.

The way this setup apparently worked was that, as soon as I or
fancontrol wrote something to /sys/bus/i2c/devices/.../pwm2 (which
controls the CPU fan), the Quiet Fan BIOS stopped controlling the fan,
so they worked together beautifully.

After the upgrade to 2.6.19.2, this no longer works that way. E.g., I
write to pwm2 and read it right back, like this:

echo 100 >pwm2; cat pwm2

That usually displays the number (100) I wrote, but a short time
later, pwm2 contains some other number, apparently what the Quiet Fan
BIOS deems appropriate.

I managed to work around this problem by disabling Quiet Fan in the
BIOS; then writing to pwm2 and fancontrol work as they have before.

That workaround is good enough for me, but I still wonder why the
change in kernels had this effect, and if there is a way to get the
old behaviour back. Any ideas?

- anton
--
M. Anton Ertl Some things have to be seen to be believed
anton@xxxxxxxxxxxxxxxxxxxxxxxxxx Most things have to be believed to be seen
http://www.complang.tuwien.ac.at/anton/home.html
.