Re: BIOS update breaks HP2125nr backlight keys

[Ryan May <rmay@ou.edu>]

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Peter Clifton wrote:
> On Thu, 2007-08-16 at 18:34 -0500, Ryan May wrote:
>> Hi,
>>
>> I recently updated the BIOS on my HP Pavilion dv2125nr laptop to F.34
>> (to enable the virtualization instructions).  Since I did this, the Fn
>> keys to control brightness have failed to work properly under Linux,
>> though they work fine before booting (ie. at Grub).  Hitting the Fn keys
>> caused the brightness to change to the minimum possible.  In fact,
>> /proc/acpi/video/VGA/LCD/brightness would show that the level was set to
>> 0 (though 20 was the lowest available).  I was still able to control the
>> brightness manually via /proc interface however.
>>
>> My investigations seem to indicate that HP, in their wisdom, seem to
>> have removed the _BQC method from their BIOS code.  It seems that the
>> ACPI code in Linux that handles the key events to change the brightness
>> use the _BQC method without checking for success, which explains why the
>> level being set was garbage.  However, the /proc interface for
>> brightness seems to only use device->brightness->curr to get the current
>> level.
> 
> Do you happen to see a _BCQ method in the DSDT instead? My HP nc6320 has
> that, and last time I looked, it seemed like it could plausibly be a
> Microsoft induced rename / typo, as this method is mentioned for getting
> brightness on a Windows Vista compatible box.

I didn't see it, but I'm new to trying to track down things in the DSDT,
so it's quite possible I missed it.  I've attached a gzipped acpidump.

> Did the bios update also mention any fixes for Vista compatibility?

None of the versions between my old BIOS and the one I have now mention
Vista.

Ryan

-- 
Ryan May
Graduate Research Assistant
School of Meteorology
University of Oklahoma

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