KDE brightness widget not usable

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1

Hello, it seems that the KDE brightness control widget has some issues with it’s functionality.

:~> kinfo
Operating System: openSUSE Tumbleweed 20250825
KDE Plasma Version: 6.4.4
KDE Frameworks Version: 6.17.0
Qt Version: 6.9.1
Kernel Version: 6.16.3-2.gb954ff4-default (64-bit) <- Kernel Standard Stable
Graphics Platform: Wayland
Processors: 4 × Intel® Core™ i5-6600K CPU @ 3.50GHz
Memory: 16 GiB of RAM (15.6 GiB usable)
Graphics Processor: AMD Radeon RX 640
hightower-i5-6600k:~>

On a fresh boot, both of the machines displays are shown when the brightness widget is opened. When moving the brightness slider from it’s 100% there is seemingly no effect on brightness and both displays exhibit a bluish flashing background. I believe due to Night Light when it is active.

At some point most likely after wakeup for suspend one of the displays sliders disappears completely from the widgets controls. Screenshot below.

Screenshot_20250826_214913
Screenshot_20250826_2149132295×1014 120 KB

I’ve looked around some concerning the situation and came across a reference from different operating system, to restart plasma-powerdevil.service but I do not see this service sifting through the results of # systemctl -all or # systemctl list-units --type=service --all .

# journalctl -b | grep -i "powerdevil"
Aug 26 22:40:58 hightower-i5-6600k systemd[1873]: Starting Powerdevil...
Aug 26 22:40:59 hightower-i5-6600k org_kde_powerdevil[2247]: Starting libddcutil. library built Not set at Not set. stdout_stderr_redirected=true
Aug 26 22:40:59 hightower-i5-6600k org_kde_powerdevil[2247]: Initializing libddcutil.  ddcutil version: 2.2.1, shared library: /usr/lib64/libddcutil.so.5.3.0
Aug 26 22:40:59 hightower-i5-6600k org_kde_powerdevil[2247]: [  2247] Options passed from client:
Aug 26 22:40:59 hightower-i5-6600k org_kde_powerdevil[2247]: [  2247] Applying combined libddcutil options:
Aug 26 22:40:59 hightower-i5-6600k org_kde_powerdevil[2247]: [  2247] (i2c_detect_x37) Extra x37 sleep: Sleeping for 400 milliseconds
Aug 26 22:40:59 hightower-i5-6600k org_kde_powerdevil[2247]: [  2247] (i2c_detect_x37) Extra x37 sleep: Sleeping for 400 milliseconds
Aug 26 22:41:00 hightower-i5-6600k org_kde_powerdevil[2247]: [  2247] (i2c_detect_x37) Extra x37 sleep: Sleeping for 400 milliseconds
Aug 26 22:41:00 hightower-i5-6600k org_kde_powerdevil[2247]: [  2247] (i2c_detect_x37) Extra x37 sleep: Sleeping for 400 milliseconds
Aug 26 22:41:00 hightower-i5-6600k org_kde_powerdevil[2247]: [  2247] (i2c_detect_x37) Extra x37 sleep: Sleeping for 400 milliseconds
Aug 26 22:41:01 hightower-i5-6600k org_kde_powerdevil[2247]: [  2247] (i2c_detect_x37) Extra x37 sleep: Sleeping for 400 milliseconds
Aug 26 22:41:03 hightower-i5-6600k org_kde_powerdevil[2247]: Library initialization complete.
Aug 26 22:41:03 hightower-i5-6600k org_kde_powerdevil[2247]: Watching for DPMS state changes unimplemented
Aug 26 22:41:03 hightower-i5-6600k org_kde_powerdevil[2247]: [  2247] Watching for DPMS state changes unimplemented
Aug 26 22:41:03 hightower-i5-6600k org_kde_powerdevil[2247]: [  2247] Watching for display connection changes, resolved watch mode = Watch_Mode_Xevent, poll loop interval = 100 millisec
Aug 26 22:41:03 hightower-i5-6600k org_kde_powerdevil[2247]: [  2247]                                          extra_stabilization_millisec: 0,  stabilization_poll_millisec: 100
Aug 26 22:41:03 hightower-i5-6600k org_kde_powerdevil[2247]: [  2247] libddcutil recheck thread 0x558bbca08980 started
Aug 26 22:41:03 hightower-i5-6600k org_kde_powerdevil[2247]: [  2431] (dw_recheck_displays_func) Recheck interval: Sleeping for 200 milliseconds
Aug 26 22:41:03 hightower-i5-6600k org_kde_powerdevil[2247]: [  2247] libddcutil watch thread 0x558bbca089e0 started
Aug 26 22:41:04 hightower-i5-6600k systemd[1]: Created slice Slice /system/dbus-:1.2-org.kde.powerdevil.discretegpuhelper.
Aug 26 22:41:04 hightower-i5-6600k systemd[1]: Started dbus-:1.2-org.kde.powerdevil.discretegpuhelper@0.service.
Aug 26 22:41:04 hightower-i5-6600k systemd[1]: Created slice Slice /system/dbus-:1.2-org.kde.powerdevil.chargethresholdhelper.
Aug 26 22:41:04 hightower-i5-6600k systemd[1]: Started dbus-:1.2-org.kde.powerdevil.chargethresholdhelper@0.service.
Aug 26 22:41:04 hightower-i5-6600k systemd[1]: Created slice Slice /system/dbus-:1.2-org.kde.powerdevil.backlighthelper.
Aug 26 22:41:04 hightower-i5-6600k systemd[1]: Started dbus-:1.2-org.kde.powerdevil.backlighthelper@0.service.
Aug 26 22:41:04 hightower-i5-6600k backlighthelper[2488]: org.kde.powerdevil: no kernel backlight interface found
Aug 26 22:41:04 hightower-i5-6600k org_kde_powerdevil[2247]: org.kde.powerdevil: org.kde.powerdevil.chargethresholdhelper.getthreshold failed "Charge thresholds are not supported by the kernel for this hardware"
Aug 26 22:41:04 hightower-i5-6600k org_kde_powerdevil[2247]: org.kde.powerdevil: org.kde.powerdevil.backlighthelper.brightness failed
Aug 26 22:41:04 hightower-i5-6600k systemd[1873]: Started Powerdevil.
Aug 26 22:41:04 hightower-i5-6600k org_kde_powerdevil[2247]: org.kde.powerdevil: Handle button events action could not check for screen configuration
Aug 26 22:41:04 hightower-i5-6600k org_kde_powerdevil[2247]: org.kde.powerdevil: org.kde.powerdevil.chargethresholdhelper.getthreshold failed "Charge thresholds are not supported by the kernel for this hardware"
Aug 26 22:41:14 hightower-i5-6600k systemd[1]: dbus-:1.2-org.kde.powerdevil.chargethresholdhelper@0.service: Deactivated successfully.
Aug 26 22:41:14 hightower-i5-6600k systemd[1]: dbus-:1.2-org.kde.powerdevil.discretegpuhelper@0.service: Deactivated successfully.
Aug 26 22:41:14 hightower-i5-6600k systemd[1]: dbus-:1.2-org.kde.powerdevil.backlighthelper@0.service: Deactivated successfully.
Aug 26 22:41:55 hightower-i5-6600k sudo[4547]:     paul : TTY=pts/0 ; PWD=/home/paul ; USER=root ; COMMAND=/usr/bin/systemctl status plasma-powerdevil.service
Aug 26 22:42:00 hightower-i5-6600k drkonqi-coredump-processor[2241]: "/usr/libexec/org_kde_powerdevil" 5884 "/var/lib/systemd/coredump/core.org_kde_powerde.1000.9d901a988a554dd0af040255845ccd5d.5884.1749085720000000.zst"
hightower-i5-6600k:~ #

The line containing Aug 26 22:41:04 hightower-i5-6600k org_kde_powerdevil[2247]: org.kde.powerdevil: org.kde.powerdevil.backlighthelper.brightness failed

The line containing "Charge thresholds are not supported by the kernel for this hardware"

Which systemD service does openSUSE use to control the KDE brightness widget? By using Kernel Standard Stable is this creating an issue? I have tried Kernel Longterm with the same outcome.

What are your thoughts about how this may be repaired?

2

Can you try ‘acpi_backlight=native’ as kernel parameter?

1 Like
3

@R7XF This does seem to help quite well and consistently with the LG monitor. The Nec does not respond to this nearly as well but is somewhat sporadically able to be adjusted. The Nec takes quite alot of time to reclaim it’s brightness level to 100% after being lowered.

This seems like a step in the correct direction.

-Thanks

1 Like
4

Show zypper lr -d. And elaborate on this:

Why is that? It is untested.

5

@knurpht no, it’s released… kernel-source (6.16.1 → 6.16.3)

6

Not @panorain’s kernel:

knurpht@Lenovo-P16:~> LANG=C zypper se -si kernel-default
Loading repository data...
Reading installed packages...

S  | Name                 | Type    | Version    | Arch   | Repository
---+----------------------+---------+------------+--------+------------------
i+ | kernel-default       | package | 6.16.1-1.1 | x86_64 | (System Packages)
i+ | kernel-default       | package | 6.16.0-1.1 | x86_64 | (System Packages)
i+ | kernel-default       | package | 6.16.3-1.1 | x86_64 | repo-oss
i  | kernel-default-devel | package | 6.16.1-1.1 | x86_64 | (System Packages)
i  | kernel-default-devel | package | 6.16.0-1.1 | x86_64 | (System Packages)
i  | kernel-default-devel | package | 6.16.3-1.1 | x86_64 | repo-oss
knurpht@Lenovo-P16:~>

where his is 6.13.3.2, so not from the stock TW repo

7

@panorain just check the journal, journalctl -b | grep backlight you may find there are competing services for control…

8

Able to access machine now since last message.

@malcolmlewis Hi, are you able to see anything out of this?

# journalctl -b | grep backlight
Sep 11 19:12:29 hightower-i5-6600k kernel: Command line: BOOT_IMAGE=/boot/vmlinuz-6.16.3-2.gb954ff4-default root=/dev/mapper/system-root resume=/dev/syste
m/swap splash=none plymouth.enable=0 security=selinux selinux=1 amdgpu.dc=1 exp_hw_support=1 deep_color=1 sched_hw_submission=4 benchmark=1 acpi_backlight
=native mitigations=auto
Sep 11 19:12:29 hightower-i5-6600k kernel: Kernel command line: BOOT_IMAGE=/boot/vmlinuz-6.16.3-2.gb954ff4-default root=/dev/mapper/system-root resume=/de
v/system/swap splash=none plymouth.enable=0 security=selinux selinux=1 amdgpu.dc=1 exp_hw_support=1 deep_color=1 sched_hw_submission=4 benchmark=1 acpi_ba
cklight=native mitigations=auto
Sep 11 19:12:29 hightower-i5-6600k dracut-cmdline[244]: Using kernel command line parameters: rd.driver.pre=btrfs rd.luks.uuid=luks-d095bece-13e0-47ca-b2
a9-f6119d3989fc rd.lvm.lv=system/swap rd.lvm.lv=system/root resume=UUID=e736498b-60e5-4f99-99c2-8a6850a78ca9 root=UUID=605560ad-fe93-4d09-8760-df0725b43
ee1 rootfstype=btrfs rootflags=rw,relatime,seclabel,ssd,space_cache,subvolid=3656,subvol=/@/.snapshots/2767/snapshot,subvol=@/.snapshots/2767/snapshot B
OOT_IMAGE=/boot/vmlinuz-6.16.3-2.gb954ff4-default root=/dev/mapper/system-root resume=/dev/system/swap splash=none plymouth.enable=0 security=selinux seli
nux=1 amdgpu.dc=1 exp_hw_support=1 deep_color=1 sched_hw_submission=4 benchmark=1 acpi_backlight=native mitigations=auto
Sep 11 19:13:23 hightower-i5-6600k systemd[1]: Created slice Slice /system/dbus-:1.2-org.kde.powerdevil.backlighthelper.
Sep 11 19:13:23 hightower-i5-6600k systemd[1]: Started dbus-:1.2-org.kde.powerdevil.backlighthelper@0.service.
Sep 11 19:13:23 hightower-i5-6600k backlighthelper[4338]: org.kde.powerdevil: no kernel backlight interface found
Sep 11 19:13:23 hightower-i5-6600k org_kde_powerdevil[4184]: org.kde.powerdevil: org.kde.powerdevil.backlighthelper.brightness failed
Sep 11 19:13:33 hightower-i5-6600k systemd[1]: dbus-:1.2-org.kde.powerdevil.backlighthelper@0.service: Deactivated successfully.

The plasma-powerdevil.service will not restart and dumps core.

# systemctl --user restart plasma-powerdevil.service
Job for plasma-powerdevil.service failed because a fatal signal was delivered causing the control process to dump core.
See "systemctl --user status plasma-powerdevil.service" and "journalctl --user -xeu plasma-powerdevil.service" for details.

# journalctl --user -xeu plasma-powerdevil.service
░░ 
░░ The process' exit code is 'dumped' and its exit status is 6.
Sep 12 16:02:01 hightower-i5-6600k systemd[9623]: plasma-powerdevil.service: Failed with result 'core-dump'.
░░ Subject: Unit failed
░░ Defined-By: systemd
░░ Support: https://lists.freedesktop.org/mailman/listinfo/systemd-devel
░░ 
░░ The unit UNIT has entered the 'failed' state with result 'core-dump'.
Sep 12 16:02:01 hightower-i5-6600k systemd[9623]: Failed to start Powerdevil.
░░ Subject: A start job for unit UNIT has failed
░░ Defined-By: systemd
░░ Support: https://lists.freedesktop.org/mailman/listinfo/systemd-devel
░░ 
░░ A start job for unit UNIT has finished with a failure.
░░ 
░░ The job identifier is 91 and the job result is failed.
Sep 12 16:02:01 hightower-i5-6600k systemd[9623]: plasma-powerdevil.service: Scheduled restart job, restart counter is at 5.
░░ Subject: Automatic restarting of a unit has been scheduled
░░ Defined-By: systemd
░░ Support: https://lists.freedesktop.org/mailman/listinfo/systemd-devel
░░ 
░░ Automatic restarting of the unit UNIT has been scheduled, as the result for
░░ the configured Restart= setting for the unit.
Sep 12 16:02:01 hightower-i5-6600k systemd[9623]: plasma-powerdevil.service: Start request repeated too quickly.
Sep 12 16:02:01 hightower-i5-6600k systemd[9623]: plasma-powerdevil.service: Failed with result 'core-dump'.
░░ Subject: Unit failed
░░ Defined-By: systemd
░░ Support: https://lists.freedesktop.org/mailman/listinfo/systemd-devel
░░ 
░░ The unit UNIT has entered the 'failed' state with result 'core-dump'.
Sep 12 16:02:01 hightower-i5-6600k systemd[9623]: Failed to start Powerdevil.
░░ Subject: A start job for unit UNIT has failed
░░ Defined-By: systemd
░░ Support: https://lists.freedesktop.org/mailman/listinfo/systemd-devel
░░ 
░░ A start job for unit UNIT has finished with a failure.
░░ 
░░ The job identifier is 107 and the job result is failed.

# systemctl --user status plasma-powerdevil.service
× plasma-powerdevil.service - Powerdevil
     Loaded: loaded (/usr/lib/systemd/user/plasma-powerdevil.service; static)
    Drop-In: /root/.config/systemd/user/plasma-powerdevil.service.d
             └─override.conf
     Active: failed (Result: core-dump) since Fri 2025-09-12 16:02:01 CDT; 47s ago
 Invocation: 3ce0f621c7a14d59b97d924d4294b3f5
    Process: 9773 ExecStart=/usr/libexec/org_kde_powerdevil (code=dumped, signal=ABRT)
   Main PID: 9773 (code=dumped, signal=ABRT)

Sep 12 16:02:01 hightower-i5-6600k systemd[9623]: plasma-powerdevil.service: Main process exited, code=dumped, status=6/ABRT
Sep 12 16:02:01 hightower-i5-6600k systemd[9623]: plasma-powerdevil.service: Failed with result 'core-dump'.
Sep 12 16:02:01 hightower-i5-6600k systemd[9623]: Failed to start Powerdevil.
Sep 12 16:02:01 hightower-i5-6600k systemd[9623]: plasma-powerdevil.service: Scheduled restart job, restart counter is at 5.
Sep 12 16:02:01 hightower-i5-6600k systemd[9623]: plasma-powerdevil.service: Start request repeated too quickly.
Sep 12 16:02:01 hightower-i5-6600k systemd[9623]: plasma-powerdevil.service: Failed with result 'core-dump'.
Sep 12 16:02:01 hightower-i5-6600k systemd[9623]: Failed to start Powerdevil.

@knurpht Hi there,

# zypper lr -d
#  | Alias                                      | Name                          | Enabled | GPG Check | Refresh | Keep | Priority | Type   | URI                                                                                  | Service
---+--------------------------------------------+-------------------------------+---------+-----------+---------+------+----------+--------+--------------------------------------------------------------------------------------+---------
 1 | Games                                      | Games                         | Yes     | (r ) Yes  | Yes     | -    |   99     | rpm-md | https://download.opensuse.org/repositories/games/openSUSE_Tumbleweed/                | 
 2 | Kernel:HEAD_KMP_standard_                  | Kernel:HEAD KMP standard      | No      | ----      | ----    | -    |   99     | rpm-md | https://download.opensuse.org/repositories/Kernel:/HEAD:/KMP/standard/               | 
 3 | Kernel_builds_for_branch_stable_standard_1 | Kernel builds for branch st-> | Yes     | (r ) Yes  | Yes     | -    |   99     | rpm-md | https://download.opensuse.org/repositories/Kernel:/stable/standard/                  | 
 4 | Multimedia-Proaudio                        | download.opensuse.org-multi-> | No      | ----      | ----    | -    |   99     | rpm-md | https://download.opensuse.org/repositories/multimedia:/proaudio/openSUSE_Tumbleweed/ | 
 5 | Nvidia                                     | Nvidia                        | No      | ----      | ----    | -    |   99     | rpm-md | https://download.nvidia.com/opensuse/tumbleweed/                                     | 
 6 | drankinatty                                | drankinatty (Nvidia G05)      | No      | ----      | ----    | -    |   99     | rpm-md | https://download.opensuse.org/repositories/home:/liguros/openSUSE_Tumbleweed/        | 
 7 | libdvdcss2                                 | libdvdcss2                    | Yes     | (r ) Yes  | Yes     | -    |   99     | rpm-md | https://opensuse-guide.org/repo/openSUSE_Tumbleweed/                                 | 
 8 | openSUSE:repo-non-oss                      | repo-non-oss                  | Yes     | (r ) Yes  | Yes     | -    |   99     | rpm-md | http://cdn.opensuse.org/tumbleweed/repo/non-oss                                      | openSUSE
 9 | openSUSE:repo-openh264                     | repo-openh264                 | Yes     | (r ) Yes  | Yes     | -    |   99     | rpm-md | https://codecs.opensuse.org/openh264/openSUSE_Tumbleweed                             | openSUSE
10 | openSUSE:repo-oss                          | repo-oss                      | Yes     | (r ) Yes  | Yes     | -    |   99     | rpm-md | http://cdn.opensuse.org/tumbleweed/repo/oss                                          | openSUSE
11 | openSUSE:repo-oss-debug                    | repo-oss-debug                | No      | ----      | ----    | -    |   99     | rpm-md | http://cdn.opensuse.org/debug/tumbleweed/repo/oss                                    | openSUSE
12 | openSUSE:repo-oss-source                   | repo-oss-source               | No      | ----      | ----    | -    |   99     | rpm-md | http://cdn.opensuse.org/source/tumbleweed/repo/oss                                   | openSUSE
13 | openSUSE:update-tumbleweed                 | update-tumbleweed             | Yes     | (r ) Yes  | Yes     | -    |   99     | rpm-md | http://cdn.opensuse.org/update/tumbleweed                                            | openSUSE
14 | packman-essentials                         | packman-essentials            | Yes     | (r ) Yes  | Yes     | -    |   98     | rpm-md | https://ftp.gwdg.de/pub/linux/misc/packman/suse/openSUSE_Tumbleweed/Essentials       |

I use kernel from stable branch - openSUSE Kernel right now on the machine.

Should I open a bug report with KDE or openSUSE Bugzilla about this?

9

@panorain get rid of the above kernel boot option, reboot and run the journal command again…

10

@malcolmlewis I removed acpi_backlight=native then updated bootloader and rebooted.

# journalctl -b | grep backlight
Sep 12 16:25:48 hightower-i5-6600k systemd[1]: Created slice Slice /system/dbus-:1.2-org.kde.powerdevil.backlighthelper.
Sep 12 16:25:48 hightower-i5-6600k systemd[1]: Started dbus-:1.2-org.kde.powerdevil.backlighthelper@0.service.
Sep 12 16:25:48 hightower-i5-6600k backlighthelper[2593]: org.kde.powerdevil: no kernel backlight interface found
Sep 12 16:25:48 hightower-i5-6600k org_kde_powerdevil[2320]: org.kde.powerdevil: org.kde.powerdevil.backlighthelper.brightness failed
Sep 12 16:25:58 hightower-i5-6600k systemd[1]: dbus-:1.2-org.kde.powerdevil.backlighthelper@0.service: Deactivated successfully.

# journalctl --user -xeu plasma-powerdevil.service
-- No entries --

# systemctl --user status plasma-powerdevil.service
○ plasma-powerdevil.service - Powerdevil
     Loaded: loaded (/usr/lib/systemd/user/plasma-powerdevil.service; static)
    Drop-In: /root/.config/systemd/user/plasma-powerdevil.service.d
             └─override.conf
     Active: inactive (dead)
11

@panorain wonder if it’s SELinux related, but that’s just a guess. If you set the native option back you do get some sort of control?

12

@malcolmlewis

The native option sometimes displays both monitors in brightness widget. The Nec monitor brightness control slides but it does not affect the display itself.

I have experienced using acpi_backlight=nativedoes not allow brightness control of the NEC monitor much of the time either.

Examining KDE Bugs for similar reference (first link in particular).
https://bugs.kde.org/show_bug.cgi?id=482713
https://bugs.kde.org/show_bug.cgi?id=506706

SELinux audit log shows nothing.

# ausearch -ts boot -m avc,user_avc,selinux_err,user_selinux_err
<no matches>

Turned off SELinux with selinux=0in grub cmdline, updated grub and rebooted, it did not help…

:~> sestatus
SELinux status:                 disabled

I also tested with older 6.9.9-1-default kernel and the same journal output and brightness widget behavior exists.

Cubicle Nate has an article about this issue :< Fix KDE Plasma Brightness Control Disappear Issue Easily

The temporary solution found there is:
systemctl --user restart plasma-powerdevil.service

Trying the solution found at Cubicle Nates results in error on this machine
unfortunately.

# systemctl --user restart plasma-powerdevil.service
Job for plasma-powerdevil.service failed because a fatal signal was delivered causing the control process to dump core.
See "systemctl --user status plasma-powerdevil.service" and "journalctl --user -xeu plasma-powerdevil.service" for details.

sudo systemctl --user restart plasma-powerdevil.service
Failed to connect to user scope bus via local transport: $DBUS_SESSION_BUS_ADDRESS and $XDG_RUNTIME_DIR not defined (consider using --machine=<user>@.host --user to connect to bus of other user)

Using root or sudo withthe command results in different error messages.

13

You run that command as a regular user (of the active desktop session).
systemctl --user restart plasma-powerdevil.service

14

@deano-ferrari Thank you for sharing that.

Passing the command as user results in the following:

:~> systemctl --user status plasma-powerdevil.service
● plasma-powerdevil.service - Powerdevil
     Loaded: loaded (/usr/lib/systemd/user/plasma-powerdevil.service; static)
     Active: active (running) since Fri 2025-09-12 17:48:11 CDT; 3min 36s ago
 Invocation: 99eae08e4e4e42449274258c725fcb1a
   Main PID: 6422 (org_kde_powerde)
      Tasks: 11 (limit: 19062)
        CPU: 561ms
     CGroup: /user.slice/user-1000.slice/user@1000.service/background.slice/plasma-powerdevil.service
             └─6422 /usr/libexec/org_kde_powerdevil

Sep 12 17:48:10 hightower-i5-6600k org_kde_powerdevil[6422]: [  6422] Watching for display connection changes, resolved watch mode = Watch_Mode_Xevent, poll loop interval = 100 millisec
Sep 12 17:48:10 hightower-i5-6600k org_kde_powerdevil[6422]: [  6422]                                          extra_stabilization_millisec: 0,  stabilization_poll_millisec: 100
Sep 12 17:48:10 hightower-i5-6600k org_kde_powerdevil[6422]: [  6422] libddcutil recheck thread 0x564539cebd20 started
Sep 12 17:48:10 hightower-i5-6600k org_kde_powerdevil[6422]: [  6422] libddcutil watch thread 0x564539d06be0 started
Sep 12 17:48:10 hightower-i5-6600k org_kde_powerdevil[6422]: [  6449] (dw_recheck_displays_func) Recheck interval: Sleeping for 200 milliseconds
Sep 12 17:48:11 hightower-i5-6600k org_kde_powerdevil[6422]: org.kde.powerdevil: org.kde.powerdevil.chargethresholdhelper.getthreshold failed "Charge thresholds are not supported by the kernel for this hardware"
Sep 12 17:48:11 hightower-i5-6600k org_kde_powerdevil[6422]: org.kde.powerdevil: org.kde.powerdevil.backlighthelper.brightness failed
Sep 12 17:48:11 hightower-i5-6600k systemd[1848]: Started Powerdevil.
Sep 12 17:48:11 hightower-i5-6600k org_kde_powerdevil[6422]: org.kde.powerdevil: Handle button events action could not check for screen configuration
Sep 12 17:48:11 hightower-i5-6600k org_kde_powerdevil[6422]: org.kde.powerdevil: org.kde.powerdevil.chargethresholdhelper.getthreshold failed "Charge thresholds are not supported by the kernel for this hardware"
15

This is key.

What is shown by ls -l /sys/class/backlight/?

16

ls -l /sys/class/backlight/
total 0

:cold_face:

17

Ok, so no backlight device present. That explains why the desktop widget does not work.

You could try the following kernel parameters one at a time (replacing the acpi_backlight=nativeparameter you are currently using)…

acpi_backlight=vendor
amdgpu.backlight=0

Also try with none of these parameters added. Reboot each time and test.

18

BTW, I noticed that in the opening post you shared the graphics hardware as “Graphics Processor: AMD Radeon RX 640”, and amongst the the repos you have configured is the NVIDIA repo

5 | Nvidia                                     | Nvidia                        | No      | ----      | ----    | -    |   99     | rpm-md | https://download.nvidia.com/opensuse/tumbleweed/                                     |

Why is that? Can you share the graphics environment and hardware details more definitively please?
inxi -SGaz

19

I have now tried all 4 options below.

acpi_backlight=video
acpi_backlight=vendor
acpi_backlight=native
amdgpu.backlight=0

In general none of the options above work correctly. Should I be observing dmesg and/or journal output after trying each of the above entries also?

A couple options are able to dim but not revert display brightness after generally one use. Then the NEC monitor disappears from the widget.

Previously this machine had an Nvidia Quadro K600 GPU installed. It has been removed for some time now.

:~> inxi -SGaz
System:
  Kernel: 6.16.7-2.g4e78a24-default arch: x86_64 bits: 64 compiler: gcc
    v: 15.2.0 clocksource: tsc avail: hpet,acpi_pm
    parameters: BOOT_IMAGE=/boot/vmlinuz-6.16.7-2.g4e78a24-default
    root=/dev/mapper/system-root resume=/dev/system/swap splash=none
    plymouth.enable=0 security=selinux selinux=1 amdgpu.dc=1 exp_hw_support=1
    deep_color=1 sched_hw_submission=4 benchmark=1 mitigations=auto
    acpi_backlight=video
  Desktop: KDE Plasma v: 6.4.5 tk: Qt v: N/A info: frameworks v: 6.17.0
    wm: kwin_wayland tools: avail: xscreensaver vt: 3 dm: SDDM Distro: openSUSE
    Tumbleweed 20250911
Graphics:
  Device-1: Advanced Micro Devices [AMD/ATI] Lexa [Radeon 540X/550X/630 / RX
    640 E9171 MCM] vendor: Dell driver: amdgpu v: kernel arch: GCN-4
    code: Arctic Islands process: GF 14nm built: 2016-20 pcie: gen: 3
    speed: 8 GT/s lanes: 8 ports: active: DP-1,DP-3 empty: DP-2
    bus-ID: 01:00.0 chip-ID: 1002:6987 class-ID: 0300 temp: 58.0 C
  Device-2: HP HP Webcam HD-2200 driver: snd-usb-audio,uvcvideo type: USB
    rev: 2.0 speed: 480 Mb/s lanes: 1 mode: 2.0 bus-ID: 1-11:5
    chip-ID: 03f0:a707 class-ID: 0102
  Display: wayland server: X.org v: 1.21.1.15 with: Xwayland v: 24.1.8
    compositor: kwin_wayland driver: X: loaded: amdgpu
    unloaded: modesetting,vesa alternate: fbdev dri: radeonsi gpu: amdgpu
    d-rect: 4480x2160 display-ID: 0
  Monitor-1: DP-1 pos: primary,top-left model: NEC EA294WMi serial: <filter>
    built: 2013 res: mode: 2560x1080 hz: 60 scale: 100% (1) dpi: 97 gamma: 1.2
    size: 673x284mm (26.5x11.18") diag: 730mm (28.8") modes: max: 2560x1080
    min: 720x400
  Monitor-2: DP-3 pos: bottom-r model: LG (GoldStar) IPS FULLHD built: 2014
    res: mode: 1920x1080 hz: 60 scale: 100% (1) dpi: 102 gamma: 1.2
    size: 480x270mm (18.9x10.63") diag: 551mm (21.7") ratio: 16:9 modes:
    max: 1920x1080 min: 720x400
  API: EGL v: 1.5 hw: drv: amd radeonsi platforms: device: 0 drv: radeonsi
    device: 1 drv: swrast gbm: drv: kms_swrast surfaceless: drv: radeonsi
    wayland: drv: radeonsi x11: drv: radeonsi
  API: OpenGL v: 4.6 compat-v: 4.5 vendor: amd mesa v: 25.2.2 glx-v: 1.4
    direct-render: yes renderer: AMD Radeon RX 640 (radeonsi polaris12 ACO DRM
    3.64 6.16.7-2.g4e78a24-default) device-ID: 1002:6987 memory: 3.91 GiB
    unified: no display-ID: :1.0
  API: Vulkan v: 1.4.321 layers: 5 device: 0 type: discrete-gpu name: AMD
    Radeon RX 640 (RADV POLARIS12) driver: mesa radv v: 25.2.2
    device-ID: 1002:6987 surfaces: N/A device: 1 type: cpu name: llvmpipe
    (LLVM 20.1.8 256 bits) driver: mesa llvmpipe v: 25.2.2 (LLVM 20.1.8)
    device-ID: 10005:0000 surfaces: N/A
  Info: Tools: api: clinfo, eglinfo, glxinfo, vulkaninfo
    de: kscreen-console,kscreen-doctor gpu: amdgpu_top wl: wayland-info
    x11: xdpyinfo, xprop, xrandr
hightower-i5-6600k:~>

 :~> kscreen-doctor -o 
Output: 1 DP-1 ca582695-bf7d-4e37-979b-62beef14a166
        enabled
        connected
        priority 2
        DisplayPort
        replication source:0
        Modes:  1:2560x1080@60*!  2:1920x1080@60  3:1920x1080@50  4:1680x1050@60  5:1400x1050@60  6:1280x1080@60  7:1280x1024@75  8:1280x1024@60  9:1440x900@60  10:1280x960@60  11:1280x800@60  12:1152x864@75  13:1280x720@60  14:1280x720@60  15:1280x720@50  16:1024x768@75  17:1024x768@70  18:1024x768@60  19:832x624@75  20:800x600@75  21:800x600@72  22:800x600@60  23:800x600@56  24:720x576@50  25:720x480@60  26:720x480@60  27:640x480@75  28:640x480@73  29:640x480@67  30:640x480@60  31:640x480@60  32:720x400@70  33:1600x900@60  34:1368x768@60 
        Geometry: 0,0 2560x1080
        Scale: 1
        Rotation: 1
        Overscan: 0
        Vrr: incapable
        RgbRange: Automatic
        HDR: incapable
        Wide Color Gamut: incapable
        ICC profile: none
        Color profile source: sRGB
        Color power preference: prefer efficiency and performance
        Brightness control: unsupported
        DDC/CI: allowed
        Color resolution: automatic (10), range: [8; 16] bits per color
        Allow EDR: unsupported
Output: 2 DP-3 24ebb115-65a9-446e-83c7-d83d57e3dfef
        enabled
        connected
        priority 1
        DisplayPort
        replication source:0
        Modes:  35:1920x1080@60*!  36:1920x1080@60  37:1920x1080@60  38:1920x1080@50  39:1680x1050@60  40:1400x1050@60  41:1600x900@60  42:1280x1024@75  43:1280x1024@60  44:1440x900@60  45:1280x800@60  46:1152x864@75  47:1280x720@60  48:1280x720@60  49:1280x720@60  50:1280x720@50  51:1024x768@75  52:1024x768@60  53:800x600@75  54:800x600@60  55:720x576@50  56:720x480@60  57:720x480@60  58:720x480@60  59:720x480@60  60:640x480@75  61:640x480@60  62:640x480@60  63:640x480@60  64:720x400@70  65:1368x768@60 
        Geometry: 2560,243 1920x1080
        Scale: 1
        Rotation: 1
        Overscan: 0
        Vrr: incapable
        RgbRange: Automatic
        HDR: incapable
        Wide Color Gamut: incapable
        ICC profile: none
        Color profile source: sRGB
        Color power preference: prefer efficiency and performance
        Brightness control: supported, set to 100% and dimming to 100%
        DDC/CI: allowed
        Color resolution: automatic (10), range: [8; 16] bits per color
        Allow EDR: unsupported
hightower-i5-6600k:~>

Sometimes kscreen-doctor -o states that DDC/CI: is not allowed and other times as shown above DDC/CI: is allowed.

zypper if ddcutil

Information for package ddcutil:
--------------------------------
Repository     : repo-oss
Name           : ddcutil
Version        : 2.2.1-1.1
Arch           : x86_64
Vendor         : openSUSE
Installed Size : 1.5 MiB
Installed      : Yes
Status         : up-to-date
Source package : ddcutil-2.2.1-1.1.src
Upstream URL   : https://github.com/rockowitz/ddcutil
Summary        : Utility to query and update monitor settings

------snip-----------
20

@panorain since it’s not a laptop, then look at using vdu_controls instead created by @mchnz https://github.com/digitaltrails/vdu_controls