[Bug 70256] [snb] initial backlight brightness is zero

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=70256

Jani Nikula <jani.nikula at intel.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEEDINFO                    |RESOLVED
         Resolution|---                         |NOTOURBUG
                 CC|                            |aaron.lu at intel.com

--- Comment #16 from Jani Nikula <jani.nikula at intel.com> ---
(In reply to comment #15)
> (In reply to comment #13)
> > Hmm, this was sandy bridge though... have you upgraded your bios? (I am not
> > implying you should, I'm merely asking.)
> 
> No yet. I'll try to do upgrade too.

Please don't. That may lead to more problems.

> (In reply to comment #14)
> > Another module parameter to try: video.use_bios_initial_backlight=0.
> 
> Thanks a lot! This solves the problem. Initial values are maximum:
> 
> $ cat /sys/class/backlight/acpi_video0/brightness
> 100
> 
> $ cat /sys/class/backlight/intel_backlight/brightness
> 4845

Cool! Closing as NOTOURBUG.

Please file a new bug on Power-Video component at the kernel.org bugzilla [1].
Reference this bug and that video.use_bios_initial_backlight=0 fixes the issue,
and attach output of 'dmidecode' there.

[1] https://bugzilla.kernel.org/enter_bug.cgi?product=ACPI

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