Bug 376684

Summary:	Screen brightness can not be changed after external monitor was connected
Product:	[Unmaintained] Powerdevil	Reporter:	Matt <Matthias.Wirtz>
Component:	general	Assignee:	Plasma Bugs List <plasma-bugs-null>
Status:	RESOLVED WORKSFORME
Severity:	minor	CC:	nate, plasma-bugs-null
Priority:	NOR
Version First Reported In:	unspecified
Target Milestone:	---
Platform:	openSUSE
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:

Description Matt 2017-02-19 20:26:13 UTC

Hello,

on my laptop (Thinkpad X240) the screen brightness can be changed by Fn+F and via the battery context menu when the battery icon in the task bar is selected. Both ways work fine.

Actual Results:
When an external monitor has been connected (primary monitor) and disconnected again, the screen brightness can not be changed anymore. After a reboot everything works again.

The screen brightness can still be changed when changing the values in 
/sys/class/backlight/intel_backlight/brightness but not via Fn+F or via battery context menu. So it seems that for some reason, the /sys/class/.../brightness is not changed anymore once an external monitor was connected and disconnected again.


Expected Result:
After disconnecting the external monitor the screen brightness should be changeable.


Output of journalctl does not give obvious errors just messages like this:
kscreen.xcb.helper: RRNotify_OutputProperty (ignored)
kscreen.xcb.helper:         Output:  67
kscreen.xcb.helper:         Property:  Backlight
kscreen.xcb.helper:         State (newValue, Deleted):  0

Above messages appear in both cases: screen brightness is changeable or is not changeable.

Comment 1 Nate Graham 2017-09-05 19:30:09 UTC

I could be wrong, but this feels like it's more about KWin than the battery monitor.

Comment 2 Martin Flöser 2017-09-06 04:26:55 UTC

Yes, you are wrong. KWin is not responsible for screen brightness.

Comment 3 Matt 2017-11-24 20:05:17 UTC

Hello,

I recently updated my openSUSE from 42.2 to 42.3 and I can no longer reproduce the reported bug. Even after plugging in and unplugging again an external monitor I can still change the screen brightness.

So the bug seems to be solved. Thx to whoever solved this problem.