Now that I have spent a long time figuring this all out, drivers after 304.64 for my graphics adapter set the wrong brightness when using xrandr. Using xbacklight -set 100 sets the brightness one value below the old method /sys/power/backlight/acpi_video0. I implemented a hack and recompiled my kde-workspace-bin so powerdevil (the kde power management service) will never try to use xrandr for the brightness. This needs to be fixed so it works correctly, it is not a problem with KDE.
EDIT: If anyone else is having brightess problems please try using xbacklight -set 100 and seeing if it sets 100% brightness or going into /sys/power/backlight and trying there.
I decided to attach a debug log hoping that will somehow get some attention to this bug but it seems to come out blank.
I see this at the console:
$ sudo nvidia-bug-report.sh
[sudo] password for user:
nvidia-bug-report.sh will now collect information about your
system and create the file 'nvidia-bug-report.log.gz' in the current
directory. It may take several seconds to run. In some
cases, it may hang trying to capture data generated dynamically
by the Linux kernel and/or the NVIDIA kernel module. While
the bug report log file will be incomplete if this happens, it
may still contain enough data to diagnose your problem.
Please include the 'nvidia-bug-report.log.gz' log file when reporting
your bug via the NVIDIA Linux forum (see devtalk.nvidia.com)
or by sending email to 'linux-bugs@nvidia.com'.
Running nvidia-bug-report.sh...
If the bug report script hangs after this point consider running with
--safe-mode command line argument.
complete.
And the generated log file seems pretty bare
____________________________________________
Start of NVIDIA bug report log file. Please include this file, along
with a detailed description of your problem, when reporting a graphics
driver bug via the NVIDIA Linux forum (see devtalk.nvidia.com)
or by sending email to 'linux-bugs@nvidia.com'.
nvidia-bug-report.sh Version: 15313852
Date: Sunday 14 July 16:23:45 EST 2013
uname: Linux 3.2.0-4-amd64 #1 SMP Debian 3.2.46-1 x86_64 GNU/Linux
command line flags:
Note: I removed my host name from the output so that is working fine.
The bug tracker is not available publicly, but you can ask us for status updates.
Can you please actually attach the nvidia-bug-report.log.gz file? It consists of separate concatenated gzip segments, so if you’re using a tool to view it that doesn’t handle those correctly, that might explain why it appears to be truncated.
That’s good to hear is there anyway I can prevent the driver from exposing the control? aka disable it on the driver so I don’t need to recompile the package every update?
Still broken as of 331.38, will this ever get fixed?
FYI using nvidia-settings -a BacklightBrightness=100 shows the same problem as xbacklight -set 100.
Also is there anyway to stop the nvidia driver exposing the backlight brightness control so I could at least stop hacking up and recompiling packages!?