[xmir] XMir/unity-system-compositor stops brightness hotkeys from working

[Andrea Biolo]

the display brightness doesn't change and remains at the maximum after that I have installed the mir/xmir (sudo apt-get install unity-system-compositor). The hotkeys (fn+F5 or F6) work but the brightness is always to the max. I have a Notebook Asus k55vd with intel 4000 (and nvidia geforce 610m).

ProblemType: Bug
DistroRelease: Ubuntu 13.10
Package: unity-system-compositor 0.0.1+13.10.20130813.1-0ubuntu1
ProcVersionSignature: Ubuntu 3.11.0-1.4-generic 3.11.0-rc4
Uname: Linux 3.11.0-1-generic x86_64
ApportVersion: 2.12-0ubuntu3
Architecture: amd64
Date: Tue Aug 13 16:12:45 2013
InstallationDate: Installed on 2013-07-31 (13 days ago)
InstallationMedia: Ubuntu 13.10 "Saucy Salamander" - Alpha amd64 (20130727)
MarkForUpload: True
SourcePackage: unity-system-compositor
UpgradeStatus: No upgrade log present (probably fresh install)

[Daniel van Vugt (vanvugt)]

That is strange. Backlight brightness has nothing to do with the display server, usually.

Can you still affect the brightness by writing directly to the kernel?...

echo N > /sys/class/backlight/*/brightness

where N is some value from 0 to /sys/class/backlight/*/max_brightness

[Andrea Biolo (andrewbiolo89)]

No brightness doesn't change, this is the result:

andre@sviluppo:/sys/class/backlight$ sudo echo 5 > /sys/class/backlight/*/brightness
bash: /sys/class/backlight/*/brightness: redirezione ambigua

redirezione ambigua -> redirection ambiguous

andre@sviluppo:/sys/class/backlight$ sudo echo 5 > /sys/class/backlight/intel_backlight/brightness
bash: /sys/class/backlight/intel_backlight/brightness: Permesso negato

Permesso negato -> no permission

[Omer Akram (om26er)]

Andrea, you need to 'sudo su' first and then do the 'echo 5 > /sys/class/backlight/*/brightness'

[Andrea Biolo (andrewbiolo89)]

Yes the command (as root) "echo N > /sys/class/backlight/intel_backlight/brightness" change the brightness from 0 to 4882!

[Daniel van Vugt (vanvugt)]

OK, here's a workaround:

1. sudo apt-get install xbacklight
2. System Settings > Keyboard > Shortcuts > Custom Shortcuts ... and add shortcuts for:

Increase brightness command: xbacklight +10
Decrease brightness command: xbacklight -10

[Daniel van Vugt (vanvugt)]

Wait, no. That workaround probably won't work because the problem is that XMir's XRANDR implementation won't support xbacklight commands :(

[Andrea Biolo (andrewbiolo89)]

Yes xbacklight doesn't work!

[Daniel van Vugt (vanvugt)]

XMir 1.0 (the old Xorg extension) is now deprecated and is not being maintained or fixed. It is replaced by the new 'Xmir' binary (package 'xmir') introduced in Ubuntu 15.10 wily.

Is there any way to reproduce this bug without the old Xmir?

[Launchpad Janitor (janitor)]

[Expired for xorg-server (Ubuntu) because there has been no activity for 60 days.]

[Launchpad Janitor (janitor)]

[Expired for Unity System Compositor because there has been no activity for 60 days.]

[Launchpad Janitor (janitor)]

[Expired for Mir because there has been no activity for 60 days.]

[Launchpad Janitor (janitor)]

[Expired for The Ubuntu Power Consumption Project because there has been no activity for 60 days.]