Bug 243108

Summary:	Fn hot keys for screen brightness do not work after login
Product:	[Unmaintained] solid	Reporter:	Thomas Walter <tom0485>
Component:	powermanagement	Assignee:	Dario Freddi <drf>
Status:	RESOLVED UPSTREAM
Severity:	normal	CC:	afiestas, lordcrc
Priority:	NOR
Version:	unspecified
Target Milestone:	---
Platform:	Ubuntu
OS:	Linux
Latest Commit:		Version Fixed In:
Sentry Crash Report:

Description Thomas Walter 2010-06-29 07:12:27 UTC

Version:           unspecified (using KDE 4.4.2) 
OS:                Linux

Before login to KDE, the Fn keys for changing the brightness of the backlight work perfectly. But during the start of KDE, some program seems to catch the acpi events and obviously does not perform the correct actions. Even xev does not show any key press events for the Fn-F10 and Fn-F11 combinations.

Changing the brightness with the slider in the system tray applet works.

Reproducible: Always

Steps to Reproduce:
Boot up your Laptop to the login screen. See that the hot keys for changing the screen brightness work. Login and keep changing the brightness during loading. 

Actual Results:  
You will observe that a few seconds after login the keys stop working.

Expected Results:  
Well - the keys should still work after login :-)

Lenovo 3000 N500 with Kubuntu 10.04

Comment 1 Asbjørn 2011-09-13 19:35:10 UTC

I have the same problem in 11.10 beta. I can actually see that the screen flickers when I try to dim it down. In addition, if I manually adjust the "Screen brightness" slider in the Battery Monitor plasma widget, the screen brightness is changed. However if I click on the Battery Monitor icon it resets to 100% brightness.

Note that it resets to 100% regardless of what my current power profile says, I've set it to 80% in the Performance profile for example.

Comment 2 Dario Freddi 2011-09-26 17:47:25 UTC

Sorry - I know this bug is very old, but for any reason it got to my inbox just after the previous comment. Apparently, this appears to be a problem where the bios and KDE are trying to perform the same operation.

The previous comment, instead, seems to be related to brightness steps and not exactly to the poster's problem. For both, a trace of kded4 when the problem occurs might be surely helpful in finding out what's not working

Comment 3 Alex Fiestas 2013-03-12 12:49:48 UTC

Can you still reproduce this with 4.10 or 4.9.5 ?

Comment 4 Asbjørn 2013-03-13 00:13:46 UTC

(In reply to comment #3)
> Can you still reproduce this with 4.10 or 4.9.5 ?

With 4.10 SC (on Kubuntu 12.10) I still have issues. My laptop is a Samsung RV520 for reference, which has an i3 with integrated GPU.

I can't use the Fn+arrow keys, however echo'ing to /sys/class/backlight/acpi_video0, or /samsung in case I use acpi_backlight=vendor, works just fine.

If I mash the Fn+Arrow up/down buttons I can see that it momentarily changes the brightness and then resets. Again using /sys/class/backlight the brightness is properly changed.

Update: So, armed with this I did some hunting. This lead me to http://lists.debian.org/debian-x/2012/10/msg00138.html

I tried adding the "Backlight" "intel_backlight" option to the Device section in a xorg.conf file I generated. After doing this, the Fn keys correctly change the brightness, and the Brightness slider in the "Energy Saving" control panel applet works correctly.

Note I did NOT have to use the acpi_backlight=vendor for this.

Comment 5 Christoph Feck 2013-04-25 12:06:00 UTC

Alex, does comment #4 provide the requested information? Please set the status accordingly.

Comment 6 Alex Fiestas 2013-04-25 14:14:11 UTC

I'm  happy you found a workaround for this.

Going to close the bug as Resolved/Upstream since the bug seems to be in Intel driver, we can't do anything to fix this.

Thanks for reporting !