Hmm, it could well be that something is wonky with your laptop panel, and looking at your Xorg.0.log I see a couple lines where X seems confused by the EDID configuration your panel gives; could that be screwing up your backlight functionality?
Hmm, it could well be that something is wonky with your laptop panel, and looking at your Xorg.0.log I see a couple lines where X seems confused by the EDID configuration your panel gives; could that be screwing up your backlight functionality?