FS#41425 - systemd-backlight@.service always set brightness to 100%

Attached to Project: Arch Linux
Opened by Luca Viggiani (lviggiani) - Friday, 01 August 2014, 14:19 GMT
Last edited by Doug Newgard (Scimmia) - Friday, 01 August 2014, 15:08 GMT
Task Type Bug Report
Category Packages: Extra
Status Closed
Assigned To No-one
Architecture x86_64
Severity Low
Priority Normal
Reported Version
Due in Version Undecided
Due Date Undecided
Percent Complete 100%
Votes 0
Private No

Details

Description:
After upgrading to linux-3.15.7-1-ARCH, whenever I restart the laptop, display brightness is set to 100% instead of restoring previous session value.

Please notice that after upgrading kernel, "/sys/class/backlight/intel_backlight" doesn't exists anymore. Now I only have "/sys/class/backlight/acpi_video0".
FN keys are working fine. I don't have any kernal parameter set relevant to video
I also discovered that if I manually stop systemd-backlight@backlight:acpi_video0.service by gnome terminal (while gdm is running), cat /var/lib/systemd/backlight/pci-0000\:00\:02.0\:backlight\:acpi_video0 will show current brightness settings.
By manually restarting systemd-backlight@backlight:acpi_video0.service, the current settings is kept.

It seems to me that systemd-backlight@backlight:acpi_video0.service is automatically stopped after gdm. In that condition screen brightness goes up to 100%. Indeed, cat /var/lib/systemd/backlight/pci-0000\:00\:02.0\:backlight\:acpi_video0 after reboot will show 100.
This task depends upon

Closed by  Doug Newgard (Scimmia)
Friday, 01 August 2014, 15:08 GMT
Reason for closing:  Duplicate
Additional comments about closing:   FS#41390 
Comment by Luca Viggiani (lviggiani) - Friday, 01 August 2014, 14:20 GMT
...sorry I forgot to tell that my video card is Intel HD Graphics 3000 and I'm using lates xf86-video-intel driver
Comment by Dave Reisner (falconindy) - Friday, 01 August 2014, 14:26 GMT
> It seems to me that systemd-backlight@backlight:acpi_video0.service is automatically stopped after gdm.
Well yes, it's certainly after gdm, but it has no relation at all to gdm.

I suspect this is probably a related/dupe of  FS#41353 ...
Comment by Luca Viggiani (lviggiani) - Friday, 01 August 2014, 14:30 GMT
I did another test:

1) Set the brightness to 50% with fn keys
2) Manually stop systemd-backlight@backlight:acpi_video0.service
3) Reboot

In this case, brightness is correctly restored to 50%.
If it is not gdm, can it be related to xorg server? It look to me that when the service is stopped at wrong time when screen is always 100%
Comment by Luca Viggiani (lviggiani) - Friday, 01 August 2014, 15:07 GMT
  • Field changed: Percent Complete (100% → 0%)
Please note that bug  FS#41353  was there since long time ago to me. But before, even with that bug, display brightness was correctly restored at reboot. So the two bugs are certainly related to each other but this is new with recent kernel upgrades. Perhaps it is just a matter of stopping the service before switching to VT

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