Which KDE package to adjust screen brightness?

Help
1

I’ve installed minimum desktop kde-plasma-desktop and I don’t find any options to adjust screen brightness.

Is there a package I need to install and where would I find the options then?

I’m on debian 12.

2

I think you need powerdevil package for that

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3

Thanks, I already have it installed but where are the options for screen brightness then?

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4

To change brightness you can use the battery applet in system tray or the power kcm in systemsettings

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5

I don’t have battery icon since I’m on desktop I guess, and where exactly is “power kcm”

I don’t find any settings, can you please give me exact steps to follow?
Or perhaps a screenshot?

6

I don’t think you can control desktop brightness in KDE or any other desktop. The only one I got working was on deepin.

7

You can only control the brightness of your desktop screen if the screen supports the DDC protocol. Not all do. For ones that do, KDE’s Powerdevil power management system supports using the DDC protocol to control the screen’s brightness.

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8

Thank you for, now I learned something new to study about.

btw. I’ve installed KDE desktop on my laptop and the option to adjust brightness is there but not on my desktop, so my screen doesn’t support DDC then but I might go buy another monitor that does. thanks!

9

You’re very welcome!

10

In my case this works for the internal display, but not for my external monitor even though manually settings the brightness using ddcutil works…

11

There are still some bugs in our DDC support, and it’s quite new. You may be running into one of them. Quit a lot of work has gone into this for Plasma 6, so maybe it will be improved there.

12

If you don’t mind using a non-KDE app, then I’ve written a GUI front end for ddcutil that can run out of the KDE system tray:

https://github.com/digitaltrails/vdu_controls

For anyone that wants to create their own widget or app for KDE or any other desktop, I’ve also created a D-Bus ddcutil-service which uses libddcutil (a ddcutil offshoot) to provide a more programmer-friendly language-independent interface:

https://github.com/digitaltrails/ddcutil-service

Because the service stays running, it removes the DDC initialisation overheads associated with running the ddcutil command.

The previously mentioned vdu_controls, written in python, now optionally prefers the D-Bus service instead of the ddcutil command. When the service is used, vdu_controls brightness/contrast sliders are noticeably more responsive.

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13

Very briefly, the status for Plasma 6.0 is that if you have a laptop display, we’ll only control the brightness for that and DDC monitors otherwise. For the related reports on bugs.kde.org and further info/links, see Bug 481927 and Bug 470107.

14

@digitaltrails, what you’re working on is (imho) relevant to what some of us have been discussing on Invent. I mentioned your stuff there, feel free to monitor the discussion or chime in if you have further thoughts.

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15

Maybe too specific, but you can use night colour control (in system tray) or redshift(-gtk). Even if it’s not for night, you maybe can set it permanently to the brightness you want?

16

I solved it by installing ddcci-dkms and configuring a rule in udev that loads the modules after the drm subsystem adds card0. /sys/class/backlight gets populated with the entries for my monitors and kde brightness control works for both at the same time. without this, powerdevil ddcci control doesn’t seem to be able to drive my monitors.

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17

Can you explain how you configured the rule?
I can only control one of my dell ultrasharp screens. Both can be controlled through ddcutil from cmd line.

18

Hey there, create a 99-custom-ddcci.rules in /etc/udev/rules.d and put this content in there

KERNEL=="i2c-[0-9]*", GROUP="i2c", MODE="0660"
ACTION=="add", KERNEL=="card0", SUBSYSTEM=="drm", RUN+="/usr/local/sbin/ddcci-startup.sh"

then create ddcci-startup.sh in /usr/loca/sbin (or wherever you want to have your script). Set it up as you prefer in your system, mine just checks for the kernel version and loads the modules :slight_smile:

if your kernel version is above 6.6.32 {
    echo 'ddcci 0x37' | sudo tee /sys/bus/i2c/devices/i2c-11/new_device > /dev/null 2>&1
}

modprobe ddcci-backlight
19

Thanks for the reply, but sadly didn’t work for me. Still only one of my Dell monitors who can be adjusted from the tray icon. Can adjust both from command line.

20

Check in /sys/class/backlight if both monitors are present, otherwise you need to enable the i2c device for your second monitor and rmmod/modprobe ddcci backlight again.

After kernel 6.6.32 you need to manually enable the i2c interfaces for the displays