When running 2.6.38-rc6 from mainline my Dell Inspiron 13" boots up fine but the brightness level is too low to be useable, its barely readable at indoor conditions. However I can change the the value with /sys/class.. and with the hotkeys still it's in the range between nearly off (value 0) to barely readable (value 15 which is reported as maximum) This seems to be a regression as it works with bot 2.6.37 and 2.6.37.1 Here is what lspci says about my video related hardware 00:02.0 VGA compatible controller: Intel Corporation Mobile 4 Series Chipset Integrated Graphics Controller (rev 07) (prog-if 00 [VGA controller]) Subsystem: Dell Device 0418 Flags: bus master, fast devsel, latency 0, IRQ 43 Memory at f0000000 (64-bit, non-prefetchable) [size=4M] Memory at d0000000 (64-bit, prefetchable) [size=256M] I/O ports at 1800 [size=8] Expansion ROM at <unassigned> [disabled] Capabilities: <access denied> Kernel driver in use: i915 Kernel modules: i915 00:02.1 Display controller: Intel Corporation Mobile 4 Series Chipset Integrated Graphics Controller (rev 07) Subsystem: Dell Device 0418 Flags: bus master, fast devsel, latency 0 Memory at f0400000 (64-bit, non-prefetch
please attach the working .config for 2.6.37 and the failing .config for 2.6.38. One area of interest would be anything related to KMS. My guess is that the backlight is actually OFF, and that you may be seeing brightness applied to the faint ambient glow that some screens have. also, please try this parameter video.use_bios_initial_backlight=0 and report if it makes any difference.
Bug closed as there is no response from the bug reporter. Please feel free to reopen it if the problem still exists in the latest upstream kernel, with and without the suggestion in comment #2.