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.