I managed to get the backlight controls working with the nvidia video card in my thinkpad, but kde's handling of the backlight hotkeys is strange. When I press the "decrease brightness" button it goes down by 10 steps, but hitting "increase brightness" makes it increase by 20 steps.

Even weirder, when the kde power management stuff decreases the brightness it is capable of making much smaller steps, I think I've seen it set it to 1%, and at the very least it was a brightness level in between 1 and 5 (I've seen it set it to 5 as well), so it isn't just trying to set 1, and getting 5 or 10.

If anyone has any insight on how to fix this, please let me know!

Some system details:

Laptop: Lenovo Thinkpad W530
Distro: Debian Sid
Kernel: 3.10.5
GPU: Nvidia Quadro K2000M
Driver: nvidia 304.88
KDE: 4.10.5 (from debian sid)

trying to change the backlight via /sys/class/backlight/acpi_video0/brightness does absolutely nothing.
xorg.conf is set to enable brightness controls via: Option "RegistryDwords" "EnableBrightnessControl=1"

The size of the step for brightness keys is set to 10% of the total limit of the brightness control for your screen.

My guess would be that both KDE and something else are both trying to change the brightness in this case - given the asymmetrical nature of the brightness changes. Do you have any other power management software running, or does the Nvidia driver provide anything to help manage screen brightness?

bcooksley wrote:The size of the step for brightness keys is set to 10% of the total limit of the brightness control for your screen.

Sounds reasonable. Though I would like to tweak it. But it seems that powerdevil is able to use smaller steps, so either that's a bug, or maybe the steps that the main keys use should be changeable?

bcooksley wrote:My guess would be that both KDE and something else are both trying to change the brightness in this case - given the asymmetrical nature of the brightness changes. Do you have any other power management software running, or does the Nvidia driver provide anything to help manage screen brightness?

As far as I know nothing else is set up to control the brightness. It gets worse if I force enable the thinkpad_acpi driver to handle the backlight or try playing with the acpi_backlight kernel module.

You'd expect that both keys would cause a 20% jump if something else was getting in the way, but its just one direction. Quite confusing.

Powerdevil is able to set arbitrary percentages - either through it's D-Bus interface, or via the Battery applet (which offers a slider to allow you to change the screen brightness). As for changing the size of the step used by KDE Power Management, that would require recompiling the code after changing it. To my knowledge, there is no plan to change the amount of step used.

In regards to the asymmetric brightness changes - does this happen at the login screen as well, or does no change occur there?
Also, can you check to see if both cause "xev" events to be triggered?