I just ran a bunch of package updates, going from nvidia 460 to 470. After a reboot, just about everything has survived, except my xbacklight shortcut keys no longer work.
Background: The system brightness control keys have not worked. This is 4-year-old Ubuntu Bug 1775065. I implemented a two-prong workaround:
This has been not ideal, but good enough, for the past couple years.
Now suddenly, xbacklight does nothing. I've tried commenting out the GRUB_CMDLINE_LINUX_DEFAULT line, rebuilding grub, rebooting. Now the system brightness keys show on screen that they are changing something, but there is no change in brightness. I.e. I'm back to the original bug 1775065 state.
Under /sys/class/backlight I have nvidia_0, which is linking to ../../devices/pci0000:00/0000:00:01.0/0000:01:00.0/backlight/nvidia_0/
Thankfully I found someone describing how to use xrandr and I'm able to write xrandr --output DP-0 --brightness 0.5 and finally save my eyes. (The machine reboots into a very bright screen). There seems to be no inc/dec option like there is with xbacklight, so a bit more work to assign to hot keys.
BTW, I also installed brightnessctl package. It claimed I was at 10% brightness, when it was more like 80-100%, and changing the values didn't change the screen brightness.
My questions are:
- Is anyone else having these xbacklight problems with driver 470? And did you find a fix? Is downgrading to 460 straightforward?
- Why is this happening? Is there a new feature in driver 470? Perhaps they fixed a bug, and now I've got some other setting or workaround in the way?
- I can see there is a version 510 driver, but I think I need a kernel upgrade, probably a whole distro upgrade, to be able to install that? Not sure I can face that. Is there any reason to expect it would fix brightness controls.
