% uname -a
Linux sayori 2.6.32.14 #7 SMP PREEMPT Fri May 28 00:31:38 JST 2010 i686 GNU/Linux

% xrandr --output LVDS --set BACKLIGHT_CONTROL legacy
X Error of failed request:  160
  Major opcode of failed request:  148 (RANDR)
  Minor opcode of failed request:  15 ()
  Serial number of failed request:  19
  Current serial number in output stream:  19
zsh: exit 1     xrandr --output LVDS --set BACKLIGHT_CONTROL legacy

% xbacklight -set 50
No outputs have backlight property
zsh: exit 1     xbacklight -set 50

% xrandr --prop
Screen 0: minimum 320 x 200, current 1024 x 768, maximum 8192 x 8192
VGA1 disconnected (normal left inverted right x axis y axis)
LVDS1 connected 1024x768+0+0 (normal left inverted right x axis y axis) 0mm x 0mm
	scaling mode: Full
		supported: None         Full         Center       Full aspect
   1024x768       60.0*+   85.0     75.0     70.1     60.0
   832x624        74.6
   800x600        85.1     72.2     75.0     60.3     56.2
   640x480        85.0     72.8     75.0     59.9
   720x400        85.0
   640x400        85.1
   640x350        85.1
DP1 disconnected (normal left inverted right x axis y axis)