On my workplace Thinkpad W530 (Quadro K1000M in discrete-only mode),
"EnableBrightnessControl=1" does in fact expose a working "Backlight" property
via xrandr.
Unfortunately, Gnome is looking for a property called "BACKLIGHT", and falls
back to /sys/class/backlight when it's not found.
See https://bugs.launchpad.net/ubuntu/+source/gnome-settings-daemon/+bug/947919
I've also managed to get the nvidiabl module to work, by setting the
'type' and 'max' parameters.
Gnome prefers backlights of type "platform" over type "raw". The non-
working thinkpad_screen is type "platform", and nvidia_backlight
defaults to "raw". Setting nvidia_backlight to "platform" fixes this.
My approach for figuring out the proper value of 'max':
1. Start with EnableBrightnessControl=1 set.
2. Load nvidiabl with some value (such as 0x1000) for 'max'. (If your
backlight turns entirely off, doing step 3 should turn it back on.)
modprobe nvidiabl max=<number>
3. Use xbacklight to change brightness to some lower value, then back to 100.
(If you just try to reapply 100, it won't work.)
xbacklight -set 50; xbacklight -set 100
4. Check what the reported 'actual_brightness' and 'brightness' values are.
grep . /sys/class/backlight/nvidia_backlight/*brightness
5. If brightness and actual_brightness both equal the max_brightness value,
you've found a 'max' that works.
If actual_brightness and brightness are below max_brightness, the guess for
'max' was too high.
If they're above max_brightness, the guess for 'max' was too low.
6. As a final sanity check, I verified that the brightness slider in
gnome works smoothly (that is, brightness changes occur over the whole
range).
7. Save that max in a module config file; I tend to put all my personal
options in /etc/modprobe.d/custom.conf
options nvidiabl type=platform max=<value you found>
Now I just need to remove "EnableBrightnessControl", since as it is now,
the nvidia driver reverts to the xbacklight value (100) whenever I click
a link in an e-mail.
--
You received this bug notification because you are a member of Ubuntu-X,
which is subscribed to nvidia-graphics-drivers in Ubuntu.
https://bugs.launchpad.net/bugs/562005
Title:
Backlight controls of laptops with NVIDIA NVS and Quadro FX 880M GPUs
no longer function while using proprietary drivers
To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu-certification/+bug/562005/+subscriptions
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