Public bug reported:

OS Version:
    Description:        Ubuntu 12.10
    Release:    12.10
$ uname -a
Linux beast 3.5.0-17-generic #28-Ubuntu SMP Tue Oct 9 19:31:23 UTC 2012 x86_64 
x86_64 x86_64 GNU/Linux

Hardware:
Samsung NP300V5-S06PL (but Samsung doesn't know they made it - don't bother 
asking them about it. It's like somebody took a non-polish i7 300V5 and slapped 
polish software on it)
CPU: i7-2670QM
GPU:
 - Intel Corporation 2nd Generation Core Processor Family Integrated Graphics 
Controller (rev 09)
 - NVIDIA Corporation GF119 [GeForce GT 520MX] (by Optimus, this one is 
actually disabled with bumblebee)


xrandr --prop is setting backlight to 100%. This has some interesting effects:
 - xbacklight -set X always fades from 100% to requested brightness
 - xbacklight -dec X always works relatively to 100%
 - after switching the screen off and on (for example by a lockscreen), the 
brightness is set to 100%
 - before upgrade (on 12.04), using fn buttons under Unity was putting it into 
an endless loop of jumping between max/just a step lower brightness (while 
eating as much CPU cycles as a single core could give it :-))

sysfs acts funny too:
# cat /sys/class/backlight/acpi_video0/max_brightness 
7
# echo 2 > /sys/class/backlight/acpi_video0/brightness    # this actually sets 
the brightness
# cat /sys/class/backlight/acpi_video0/actual_brightness # shouldn't this be 2?
7
# cat /sys/class/backlight/acpi_video0/brightness
2

** Affects: ubuntu
     Importance: Undecided
         Status: New


** Tags: backlight brightness xrandr

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https://bugs.launchpad.net/bugs/1069640

Title:
  xrandr --prop sets backlight to 100%

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