Brightness Control without a Display

I’m running Arch Linux on aarch64 on a Samsung Galaxy S9. I have installed “plasma-desktop” along with necessary utilities. The only downside is that I cannot run systemd, so I’m launching things manually, such as the dbus daemon(s) and NetworkManager.

I have upowerd communicating correctly with the Plasma desktop, so the battery percentage works. However, while i have /sys/class/backlight/panel available (and writing raw values to the “brightness” attribute works), I cannot control this via the Plasma “Brightness” applet as it’s completely missing.

Am I missing a service here for brightness control, or is upowerd supposed to take care of this?

The device displays using an X socket provided by Termux:X11, but no “Display” appears connected from Plasma’s perspective. Could this be the cause?

Here is a log of “startplasma-x11”: pastebin com SZsheNMu

It seems that org_kde_powerdevil says this when loading, if launched manually:

/usr/lib/org_kde_powerdevil       
Detected locale "C" with character encoding "ANSI_X3.4-1968", which is not UTF-8.
Qt depends on a UTF-8 locale, and has switched to "C.UTF-8" instead.
If this causes problems, reconfigure your locale. See the locale(1) manual
for more information.
Could not load a session backend. Session management operations such as shutdown will not be operational. This is a setup issue.
qt.core.qobject.connect: QObject::disconnect: Unexpected nullptr parameter
qt.core.qobject.connect: QObject::disconnect: Unexpected nullptr parameter
Unable to open directory /sys/class/drm: No such file or directory
org.kde.powerdevil: [DDCutilDetector]: Failed to initialize callback
org.kde.powerdevil: org.kde.powerdevil.discretegpuhelper.hasdualgpu failed
org.kde.powerdevil: org.kde.powerdevil.chargethresholdhelper.getthreshold failed ""
org.kde.powerdevil: org.kde.powerdevil.backlighthelper.brightness failed
org.kde.kscreen.dpms: DPMS extension not available
org.kde.powerdevil: Handle button events action could not check for screen configuration
org.kde.powerdevil: org.kde.powerdevil.chargethresholdhelper.getthreshold failed ""
^C
1 Like

CC @jpetso who did a lot of screen brightness work recently