Re: [PATCH] Acer Aspire One Fan Control

From: Peter Feuerer
Date: Sun May 24 2009 - 07:18:20 EST


Borislav Petkov writes:

Yep, I don't disagree. But I strongly suspect that if you force the
fan off and overheat the machine, it will shut down in hardware before
doing any damage.

Yep, however we won't come that far with the current driver since it
relinquishes control of the fan to the BIOS after a critical temp of
89Â is reached. I'm still quite unpersuaded about that "magical" number
since it is 1 degree below the high interval boundary of the juncture
temperature of the Atom CPU. I would like to have a more reliable source
for the allowed envelope based not only on the CPU but on the whole
chipset but can't seem to find any data from Acer on that.

I think we are fine the way it is now. The driver allows to read the temperature by default and people who know what they are doing can easily enable kernel based fan control.

the module can still be toggled on/off from sysfs. Actually, empirically
measured, there seem to be three states of the fan: off, on and on-max
where you can hear it rotating at max RPM. The kernel module can handle
those completely if you know the respective ACPI EC commands and there's
no need for userspace daemon, IMHO.

It would be still nice to let the userspace lower the trip points for
maximum flexibility. No need for userspace _daemon_.

I'm sure Peter wouldn't mind adding some other sysfs entries in future
versions of the driver controlling exactly that.

You can already change the trip points via the /sys/module/acerhdf/parameters/* files on the fly.

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