Description of problem: Lenovo T440s 00:02.0 VGA compatible controller: Intel Corporation Haswell-ULT Integrated Graphics Controller (rev 0b) After being docked, when undocking the brightness controls fail to do anything. Brightness defaults to some very low value and, while the buttons appear to change the level in the pop-up, no actual change in brightness occurs. Version-Release number of selected component (if applicable): 2.21.15-5.fc20 How reproducible: Frequently. Steps to Reproduce: 1. Dock laptop 2. Set external monitor to primary, disable built-in monitor 3. Undock laptop Actual results: Brightness controls display that they are adjusting, but do not do anything. Expected results: Brightness controls should adjust screen brightness. Additional info:
Also seen on 3.13.6-100.fc19.x86_64. Temporary (and ugly) workaround is: # echo 4000 > /sys/class/backlight/intel_backlight/brightness
Not sure what I'm doing wrong, but that does not work for me: [thoraxe@t440-festive-local ~]$ cat /sys/class/backlight/intel_backlight/brightness 252 [thoraxe@t440-festive-local ~]$ echo 300 > /sys/class/backlight/intel_backlight/brightness bash: /sys/class/backlight/intel_backlight/brightness: Permission denied [thoraxe@t440-festive-local ~]$ sudo echo 500 > /sys/class/backlight/intel_backlight/brightness bash: /sys/class/backlight/intel_backlight/brightness: Permission denied [thoraxe@t440-festive-local ~]$ echo [thoraxe@t440-festive-local ~]$ [thoraxe@t440-festive-local ~]$ su - Password: Last login: Wed Mar 26 17:39:38 EDT 2014 from dumpster on pts/13 [root@t440-festive-local ~]# echo 4000 > /sys/class/backlight/intel_backlight/brightness -bash: echo: write error: Invalid argument
Happened to me some minutes ago with 3.13.9-200.fc20.x86_64 too, powering off, powering on made it come back to full bright.
There is a change in backlight handling in the 3.16 kernels which I believe will fix this. Can you give a 3.16 kernel a try? E.G. this build: http://koji.fedoraproject.org/koji/buildinfo?buildID=540927
I will try to try in the next few days!
This seems like it has been fixed for a while. Closing.