[arch-general] Display issues with Linux 3.1

Taylor Hedberg tmhedberg at gmail.com
Thu Nov 10 19:36:48 EST 2011

Sebastian Schwarz, Thu 2011-11-10 @ 16:36:54+0100:
> My display comes back with the minimal brightness setting. Also the
> XF86MonBrightnessUp (Fn+Up) and XF86MonBrightnessDown (Fn+Down)
> buttons stopped working.  I can restore the previous brightness level
> and the buttons by running:
>     cat /sys/class/backlight/intel_backlight/max_brightness \
>             > /sys/class/backlight/intel_backlight/brightness
> The bug can easily triggered in X by running:
>     xset dpms force off

Yes, this is the same behavior that I'm seeing. Writing the
max_brightness value into the sysfs brightness file restores normal
backlight brightness. I can also restore it with `xbacklight -set 100`.

> I found this I my dmesg output:
>     [Firmware Bug]: Duplicate ACPI video bus devices for the same VGA
>     controller, please try module parameter
>     "video.allow_duplicates=1"if the current driver doesn't work.
> But I also haven't tried this, as the incorrect brightness has not
> annoyed me enough, yet.

I have this message in my dmesg output as well, but unfortunately,
setting the mentioned module parameter doesn't have any effect on the
problems I'm seeing.

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