#785460 regression: screen brightness no longer saved on logout or restart

Package:
xorg
Source:
xorg
Description:
X.Org X Window System
Submitter:
Robert Lange
Date:
2015-06-25 16:03:03 UTC
Severity:
normal
#785460#5
Date:
2015-05-16 15:30:52 UTC
From:
To:
Dear Maintainer,

I have a Thinkpad w540. I use the Intel graphics and have the Nvidia card off.
I usually leave the screen at 50% brightness to conserve battery, and because
the screen to very bright.

I use testing and run apt-get dist-upgrade daily. Yesterday (2015-05-15) I got
an upgrade to Xorg. A few hours later, I rebooted and immediately noticed that
the screen was at 100% brightness. As a test, I reset the brightness to 50% and
logged out of my session. Sure enough, as soon as the login screen appeared,
the screen was back up to 100% brightness.

I will stress that this is a regression, because prior to yesterday, the screen
brightness was saved between sessions. I will also point out that the
brightness controls still work properly, it's just that the brightness setting
is no longer saved on logout or restart.
#785460#10
Date:
2015-05-16 16:21:01 UTC
From:
To:
When I set the brightness manually, I run the following and see:

$ ls -1 /sys/class/backlight/*/*brightness | xargs -I % sh -c "echo % ;
cat %"

/sys/class/backlight/intel_backlight/actual_brightness
2219
/sys/class/backlight/intel_backlight/brightness
2219
/sys/class/backlight/intel_backlight/max_brightness
4438

However, when I logout and log back in (or reboot) and run the command,
I see:

$ ls -1 /sys/class/backlight/*/*brightness | xargs -I % sh -c "echo % ;
cat %"

/sys/class/backlight/intel_backlight/actual_brightness
4438
/sys/class/backlight/intel_backlight/brightness
4438
/sys/class/backlight/intel_backlight/max_brightness
4438

There is a systemd file which apparently stores the brightness for
restoration during reboot.

$ cat
/var/lib/systemd/backlight/pci-0000\:00\:02.0\:backlight\:intel_backlight
4438

I tried manually editing the file to 2219, but upon logout and login or
reboot, the brightness was still restored to maximum and the file was
restored to 4438.
#785460#15
Date:
2015-06-24 13:13:24 UTC
From:
To:
As of an update that occurred to testing in the last week, I no longer
see this issue. Screen brightness is once again saved across reboots.
#785460#20
Date:
2015-06-25 16:00:26 UTC
From:
To:
The brightness is saved across reboots when using the kernel provided by
package linux-image-4.0.0-2-amd64, which is currently in unstable.
Unfortunately, due to other regressions, I was forced back to
linux-image-3.16.0-4-amd64, which is currently in testing, and now
brightness is not saved across reboots.