[Bug 78200] [regression] Backlight too dim to use from kernel 3.14 and systemd error

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=78200

--- Comment #10 from Jani Nikula <jani.nikula at intel.com> ---
(In reply to comment #0)
> I reverted to kernel 3.13.7-1-ARCH and the screen brightness seemed normal
> but an investigation of the systemd journal showed there were errors that
> are relevant to this issue:
> 
> May 02 17:08:49 samsung1 systemd[1]: Starting Load/Save Screen Backlight
> Brightness of backlight:intel_backlight...
> May 02 17:08:49 samsung1 systemd-backlight[191]: Failed to write system
> attribute: Invalid argument
> May 02 17:08:49 samsung1 systemd[1]:
> systemd-backlight at backlight:intel_backlight.service: main process exited,
> code=exited, status=1/FAI
> May 02 17:08:49 samsung1 systemd[1]: Failed to start Load/Save Screen
> Backlight Brightness of backlight:intel_backlight.
> May 02 17:08:49 samsung1 systemd[1]: Unit
> systemd-backlight at backlight:intel_backlight.service entered failed state.

Looking at the systemd source, it seems to me this happens because there's a
too high saved value for backlight. I don't know how it got there, but the
clamping and error handling don't take this into account. Try removing, uh, the
relevant looking files from /var/lib/systemd/backlight/ - there should be
file(s) containing the saved values, named with escaped names of the
interfaces.

If that doesn't help, try systemd.restore_state=0 on the kernel command line.
There may be a way to pass that to systemd directly too, but I'm rather
clueless about systemd details. Let us know if that helps.

Finally, please try 3.15-rc kernels; I think there's a fix or two there that
haven't propagated to stable kernels yet.

-- 
You are receiving this mail because:
You are the QA Contact for the bug.
You are on the CC list for the bug.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.freedesktop.org/archives/intel-gfx-bugs/attachments/20140507/fa19f598/attachment-0001.html>