[Bug 65351] New: Can't control laptop screen's brightness when switched to discrete card (Radeon HD 5650) on muxed laptop

[bugzilla-daemon at bugzilla.kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=65351

            Bug ID: 65351
           Summary: Can't control laptop screen's brightness when switched
                    to discrete card (Radeon HD 5650) on muxed laptop
           Product: Drivers
           Version: 2.5
    Kernel Version: Linux linux 3.12.0-1-ARCH #1 SMP PREEMPT x86_64
                    GNU/Linux
          Hardware: x86-64
                OS: Linux
              Tree: Mainline
            Status: NEW
          Severity: high
          Priority: P1
         Component: Video(DRI - Intel)
          Assignee: intel-gfx-bugs at lists.freedesktop.org
          Reporter: thequack12 at yahoo.com
                CC: intel-gfx-bugs at lists.freedesktop.org
        Regression: No

When I switch to integrated intel graphics with:
#echo "DIGD" > /sys/kernel/debug/vgaswitcheroo/switch
logout & logback in with only laptop's screen on (obviously),
I _can_ control the laptop screen's 'brightness'. But,
when I switch to discrete Radeon HD 5650 graphics with:
#echo "DDIS" > /sys/kernel/debug/vgaswitcheroo/switch
logout & logback in with both laptop's screen and external monitor 'ON' -
laptop screen's brightness becomes full, and I can't decrease the brightness!

I tried:
#echo 1000 > /sys/class/backlight/intel_backlight/brightness
but it doesn't show any effect on brightness of laptop's screen.

Also, the value in /sys/class/backlight/intel_backlight/brightness "jumps" to
arbitrary number when I "echo" number into it to "lower" the brightness.

e.g. when I do:
#cd /sys/class/backlight/intel_backlight
#echo 4882 > brightness
the value in 'brightness' file jumps to 13000 and even 64332 or something on
second try to lower the brightness.

Finally, let me know if any sort of logs or information is required...

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