On Fri, 27 Feb 2015 19:45:16 +0100 jre <jre.wine...@gmail.com> wrote: > CCing debia...@lists.debian.org and especially Maximillan Attems who > prepared xserver-xorg-video-intel 2:2.99.911-git20140529-1~exp1 which > added the backlight helper. > > Summary of what happened so far: > > intel_backlight, which is default since Linux 3.16, does not work > correctly on several laptops. They have been blacklisted in the kernel > in order to use the working ACPI backlight again. #772440 is about just > another laptop model to be added to this blacklist. > Luca Boccassi found that the new backlight helper script in > xserver-xorg-video-intel also fixes the issue. > > > > On 02/20/2015 12:29 AM, Luca Boccassi wrote: > > Cross-post from freedesktop bug, just to make sure it doesn't go unnoticed: > > > > (In reply to Luca Boccassi from comment #13) > >> Hello, > >> > >> I have a Dell Latitude E5540, running an Intel Haswell i7-4600U with GPU HD > >> Graphics 4400, and I have the same problem. But I noticed that upgrading the > >> Intel driver to a version that ships a new backlight helper binary fixes the > >> problem. > >> > >> In my case, I am running Debian Jessie. The driver is part of the package > >> xserver-xorg-video-intel and the version that ships the new backlight > >> helper, according to the changelog, is: > >> > >> xserver-xorg-video-intel (2:2.99.911+git20140529-1~exp1) experimental; > >> urgency=low > >> > >> * New upstream prerelease. (closes: #748753) > >> * Install new backlight helper. > > Confirmed, in > git://anonscm.debian.org/pkg-xorg/driver/xserver-xorg-video-intel I > found the new backlight helper script to be the relevant commit. > > Also see the ongoing discussion in > https://bugs.freedesktop.org/show_bug.cgi?id=87286. > > IMO the disable_native_backlight for some laptop models is (part of) the > correct solution and it is not clear /why/ the new backlight helper > script helps. > > Should we clone this bug as a more general one and then reassign to > xserver-xorg-video-intel? We could then try to backport the changes to > jessie to also help other affected laptops which are not yet blacklisted. > That would be the following commits + probably some follow-up fixes. At > least the 3rd commit requires manual merging: > > commit 631b4e4c78a807e61214026bf9a1461aadbd59b5 > Author: maximilian attems <maks@***> > Date: Thu May 29 17:07:16 2014 +0200 > install add new helper > > commit b71f3d8bd4d6773899c1bdc903911cf240e68ead > Author: Jan Alexander Steffens (heftig) <jan.steffens@***> > > I just fear it is too late for that in jessie.
Hello Jre, To make a random and uneducated guess, maybe something changed in the kernel-space drivers in 3.16, which requires newer userspace driver to work properly. It might have to do with this (from the upstream changelog): > Hans de Geode has been working on making the Xserver work without > privileges under the supervision of systemd/logind. This necessitated a > few new features for us: server fds (where we are passed which fd to use > to talk to our device by the Xserver who may in turn receive it from > logind or other host) and a small backlight helper so that we can continue > to provide a RandR backlight property when running without root privileges. Anyway, I did the homework, and I have a working patch that backports the required fixes from 2.99.17 on top of 2.21.15-2. I tested on my laptop and it works. I'll clone this bug, tag it, and attach the patch, so that the maintainers can decide what's the best course of action. It would indeed be nice if a fix (either backport or version bump) was added to Jessie, since for non-tech savvy users booting and finding a black screen, with the brightness control not working, is not a nice experience! Kind regards, Luca Boccassi
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