NVIDIA card Brightness HotKey not working

[Toz]

After this operation I finally got the nvidiabl interface:

aa@aa-Latitude-E6530:~$ for i in /sys/class/backlight/*; do echo $i; cat $i/brightness; cat $i/actual_brightness; cat $i/max_brightness; done
/sys/class/backlight/acpi_video0
85
86
100
/sys/class/backlight/nvidia_backlight
83
83
127

Just thought of something: does using the acpi_backlight=vendor kernel boot parameter remove the acpi_video0 interface and leave you with only the nvidia_backlight one and if so, do the brightness controls work automatically again because there is only one backlight interface recognized by the system?

[aa-hcl]

Hi,

I added acpi_backlight=vendor and with the following boot line:

aa@aa-Latitude-E6530:~$ cat /proc/cmdline 
BOOT_IMAGE=/boot/vmlinuz-3.11.0-14-generic root=UUID=c86aca8f-c879-4a03-a76a-7effda7f037d ro quiet splash acpi_backlight=vendor

I got the dell backlight interface instead of the acpi interface - in addition to nvidiabl:

aa@aa-Latitude-E6530:~$ for i in /sys/class/backlight/*; do echo $i; cat $i/brightness; cat $i/actual_brightness; cat $i/max_brightness; done
/sys/class/backlight/dell_backlight
15
9
15
/sys/class/backlight/nvidia_backlight
100
100
127

The Fn keys do not change brightness as before and in the system settings the brightness can not be changed as well. The only way I can now change the brightness changed is by (100 - for maximum brightness)

 
aa@aa-Latitude-E6530:~$ echo 100 | sudo tee /sys/class/backlight/nvidia_backlight/brightness 
100

another VERY STRANGE thing: sometimes I get the brightness changed when I open a new window to firefox: the brightness goes to the default level set by the BIOS (in this case the value for /sys/class/backlight/nvidia_backlight/brightness was not changed).
However, this did not happen always, so it might be just another error.


I would really welcome any comments!

[Toz]

You should have a module called dell-laptop loaded:

lsmod | grep dell

Try removing it:

sudo modprobe -r dell-laptop

If there are no errors, check your backlight interfaces again:

for i in /sys/class/backlight/*; do echo $i; cat $i/brightness; cat $i/actual_brightness; cat $i/max_brightness; done

...and if there is only one (nvidia_backlight), try the function keys/brightness sliders again. (Note: you may have to blacklist the dell-laptop module and restart to test fully).