Created attachment 84406 [details]
Xorg log, Vbios dump, Xrandr output, Intel reg dump files.
After upgrading to xf86-video-intel to 2.21.14 KDE can no longer control the brightness. It display the brightness level info, but no change. Downgrading to 2.21.13 solves the issue.
issuing as root:
echo _value_ > /sys/class/backlight/intel_backlight/brightness
changes the brightness.
_value_: 0 to 4882
Extra info: http://forum.kde.org/viewtopic.php?f=225&t=117153
chipset: VGA compatible controller: Intel Corporation 2nd Generation Core Processor Family Integrated Graphics Controller (rev 09)
kernel driver: i915
uname -r: 3.10.7-1-ARCH
uname -m: i686
Xorg -version: X.Org X Server 1.14.2, Release Date: 2013-06-25
Distro: Arch Linux
Laptop model: Dell Inspiron 411z-6733
The dell_backlight interface is dysfunctional and should not be exposed for your system i.e. don't specify acpi_backlight=vendor. Also i915.i915_enable_fbc=1 is known to cause issues on your system.
Thanks you for your answer.
Any suggestions? Bug report for another packet? Stay with xf86-video-intel 2.21.13?
Reoving acpi_backlight=vendor make the brightness control very erratic.
You can use Option "backlight" "intel_backlight" to override the selection of dell_backlight.