I just discovered the invert_brightness command line fix today after over a year of having this bug showing up from time to time :) This turns the backlight on after booting sudo setpci -s 00:02.0 F4.B=00 but if using the kernel parameter there is no need for setpci. Model name: Acer Aspire 4736Z lspci entries for the two graphics slots, only SDevice is different from the Aspire 5734Z Slot: 00:02.0 Class: 0300 Vendor: 8086 Device: 2a42 SVendor: 1025 SDevice: 0260 Rev: 07 Slot: 00:02.1 Class: 0380 Vendor: 8086 Device: 2a43 SVendor: 1025 SDevice: 0260 Rev: 07 I did not have the possibility to build and test a new kernel or I would have sent a patch.
Created attachment 93361 [details] add another Acer to the quirk list Please test whether this quirk entry works for you without setting the option manually, thanks.
Created attachment 93391 [details] patch I tested this patch and backlight works without having to modify the kernel command line.
Patch should land in 3.9 soon and then get backported: commit 0e4cc35b5bb871077ad7d8088792a4a0da02c18c Author: Daniel Vetter <daniel.vetter@ffwll.ch> Date: Fri Feb 15 18:35:30 2013 +0100 drm/i915: inverted brightness quirk for Acer Aspire 4736Z
A patch referencing this bug report has been merged in Linux v3.9-rc1: commit ac4199e0f047546aa40172785e26c82b54bbe811 Author: Daniel Vetter <daniel.vetter@ffwll.ch> Date: Fri Feb 15 18:35:30 2013 +0100 drm/i915: inverted brightness quirk for Acer Aspire 4736Z