Feature request: set brightness of all monitors

[piec]

Hi,

Thanks for your work on brightnessctl.

It would be practical to be able to set the brightness level of all connected monitors. For example brightnessctl -c backlight s 10+ could set the brightness of all connected "backlight" devices. I think it's not possible in the current state.

For example in my case I have:

$ ls /sys/class/backlight
amdgpu_bl0  ddcci9

What do you think?

Cheers, Pierre

PS: I could also wrap brightnessctl with a shell script and run it several times, but ... :)