Ubuntu
xserver-xorg-video-intel package

  1. Bug #417770
  2. Comment #2

Comment 2 for bug 417770

Revision history for this message
Henrik Rydberg (rydberg) wrote : Re: kernel backlight control method missing for macbooks

Bryce, thank you for your reply. The issue behind the solution patch is that when setting the xrandr BACKLIGHT_CONTROL property to 'kernel' to use the sysfs interface to control the LCD backlight, the existing sysfs backlight interface is not detected. The MacBookAir, as well as many other macbooks, use the mbp_nvidia_bl kernel module, which produces the sysfs interface /sys/class/backlight/mbp_backlight. The current intel driver code seems to list an explicit set of possible names after /sys/class/backlight/, and mbp_backlight is not one of them. Applying the supplied patch fixes the problem. The Xorg log for the working code reveals this line:

/var/log/Xorg.0.log:(II) intel(0): found backlight control method /sys/class/backlight/mbp_backlight

When the patch is not present, it searches for the first name in the list in src/i830_lvds.c (asus-latop), does not find it and outputs a corresponding error message.

Output of lspci attached.

(Rant: Marking bugs as 'incomplete' by automacy is a good way of keeping the desk clean ;-))