Comment 9 for bug 847001

This bug also affects me with 12.04. I have a Dell E6520 with Intel+NVidia (optimus). I see different timings than Sparhawk

This happened both with a fresh installation, and after installing bumblebee. In both cases optimus was ON in the bios, but in the former case the system was falling back unity2D (I believe), and after installing bumblebee it uses unity3D (though always with the intel card).

The bug happens regardless on whether the nvidia card is on (i.e. while optirun glxgears is running) or off.

The bug also happens when switched to a virtual console with CTRL-ALT-F1.

When I give one quick tap of brightness up using the laptop keyboard (Fn + Arrow up), I see the following:
- 1 second delay, nothing happens
- brightness is changed 1 step up
- 0.4 seconds delay, during which at some point the brightness popup appears
- brightness is changed another step up
- 0.4 seconds delay
- brightness is changed another step up (sometimes, and sometimes one step more).

So with one tap I get at least three brightness steps.

The same happens when reducing brighness.

During the time (roughly 2 seconds) this happens, mouse is sluggish and all animations (including opengl ones) become jerky. After, everything is normal.

Top does not show any process eating CPU.

dmesg shows nothing.

Other special keys on the laptop (i.e. keyboard brighness, sleep, touchpad off, screenshot) work fine without delays.

Also, this may be related (from 2008): http://ubuntuforums.org/showthread.php?t=777947