[Bug 87286] [i915 intel_backlight] can't regulate brightness at GDM login prompt if HDMI monitor connected

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=87286

--- Comment #19 from Luca Boccassi <luca.boccassi at gmail.com> ---
(In reply to Aaron Lu from comment #18)
> (In reply to jre.winesim from comment #16)
> > My patch has been accepted by Rafael and subsequently merged to:
> > git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/ master
> > 
> >   commit 3120d03cf64d7f9fd71231827af2c1550aa4caa7
> >   Author: Jens Reyer <jens.reyer at gmail.com>
> >   Date:   Tue Feb 17 19:07:29 2015 +0100
> >   ACPI / video: Disable native backlight on Samsung Series 9 laptops
> > 
> > Thanks Aaron Lu for guiding me through my first kernel patch submission.
> > 
> > So this bug will be fixed in Linux 3.20/4.0 and this report here may be
> > closed.
> > 
> > Still I'd like to know if there are any plans to reenable native backlight,
> > now that we know (thanks Luca Boccassi) that a newer
> > xserver-xorg-video-intel also fixes the issues. Aaron?
> 
> I'm not sure how exactly the updated xserver-xorg-video-intel package fixed
> the problem. The native backlight control interface is provided by the in
> kernel i915 driver and shouldn't be possible to be fixed by an user space
> package. If this remains true, I don't see there is a need to enable the
> native backlight interface.

Hello Aaron,

That package ships a binary, xf86-video-intel-backlight-helper, which
apparently is used to regulate the brightness. I'm not familiar with the code
myself or the project itself, but with a quick Google search this Xorg mailer
thread came up and it does shed some light on how this is used:
http://lists.x.org/archives/xorg-devel/2014-February/040575.html

Kind regards,
Luca Boccassi

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