cvs commit: src/sys/dev/acpi_support acpi_ibm.c

Markus Brueffer markus at
Fri Jan 13 17:08:20 PST 2006

Nate Lawson schrieb:
> Markus Brueffer wrote:
>> markus      2006-01-14 00:39:10 UTC
>>   FreeBSD src repository (ports committer)
>>   Modified files:
>>     sys/dev/acpi_support acpi_ibm.c   Log:
>>   - Add support for setting the fan control mode to manual or automatic
>>   - Add support for adjusting the fan speed if the fan control mode is
>> manual
>>     Documentation for the relevant embedded controller register was
>> obtained from
>>     Tested on:      R51  by Fabian Keil
>>                   T41p by markus
>>   Requested by:   many
>>   Approved by:    philip
>>   MFC after:      1 week
>>     Revision  Changes    Path
>>   1.10      +55 -3     src/sys/dev/acpi_support/acpi_ibm.c
> Thanks for adding support for this but it should be noted that this can
> be very dangerous.  If your userland app tries to control the fanspeed
> and dies, your system could overheat.  Hopefully, the BIOS will override
> the user settings if the temp gets too high but that is a longshot when
> mucking with things at this low level.

That's why I didn't add support for it in the first place. The problem
is that especially with the T43 series there seems to be a fan problem.
If it reaches a certain threshold the fan is switched on, but never
switched off regardless how cool the notebook gets.

If the new documentation in acpi_ibm(4) isn't enough, I can add bigger
warning signs:
     Indicates whether the fan is in automatic (1) or manual (0) mode.
     Default is automatic mode.  This sysctl should be used with
     extreme precaution, since disabling automatic fan control might
     overheat the ThinkPad and lead to permanent damage if the

For obvious reasons I haven't tested if the BIOS overrides the user
settings if the temp gets too high :)


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