MX Linux Forum

A search on the Raspberry Pi Forum showed some promise:

https://forums.raspberrypi.com/viewtopic.php?t=365524

Thanks @Jerry3904 for your attention to this problem, I read the post on Raspberry Pi forum, Wayland on Raspberry Pi OS etc.
I'm going to wait until someone sorts this problem out for the MX 23 respin, until then it's a piece of cardboard covering the front of the monitor held there by magnets.

OK, Susan. I would like to point out that that RPi Forum thread seems to make clear that the problem is not limited to MX-Linux or perhaps even to the Pi 5, but is inherent to RPi itself. We'll try to chase this down.

To add a data point: I tested this tool on the Official Display that runs on a Pi 4b. It had no effect on either the Buster or the Bookworm version.

i went commandline and that didn't work either. the xrandr software Brightness value was saved and set to the X session, but has no effect. Its either the way the X server is compiled or the display driver, I don't know which. Given the pi's unique graphics hardware, I tend to think target the display driver, and I'm not sure how motivated the pi folks will be to change the situation.

since all displays on the pi are external, I would be very surprised if the backlight function worked at all.

I tried that too but got nowhere, decided the command may not have been correct:

Jerry3904 wrote: Sun Jun 23, 2024 11:25 am I tried that too but got nowhere, decided the command may not have been correct:

Code: Select all

xrandr --output hdmi-1 --brightness <tried a bunch of values>

command is correct, its just not utilized.

given the target for pi devices, mostly being headless, I imagine it was totally left out of the display driver. I really don't know how all this works, but the display brightness was set.

you could try messing with gamma, which is old school but is at least a different path.

OK. I've looked at a bunch of web suggestions and at various "backlight" packages in Synaptic, but the big problem I see is that there is nothing in /sys/class/backlight/ to manipulate. I do see some 70 pkgs in a Thunar search on "backlight" but nothing I would ever know to mess with.

Jerry3904 wrote: Sun Jun 23, 2024 12:41 pm OK. I've looked at a bunch of web suggestions and at various "backlight" packages in Synaptic, but the big problem I see is that there is nothing in /sys/class/backlight/ to manipulate. I do see some 70 pkgs in a Thunar search on "backlight" but nothing I would ever know to mess with.

that's what I'm saying, its very rare you can manipulate the backlight of an external device. I think some displayport monitors can do this, but mostly no. an external monitor should have its own controls though. (don't know if the little official or kit style monitors would though).

Thanks, I wasn't getting that.

I conclude that there is a reason that RPi has no app for this...