SUMMARY The secondary monitor does not obey the "dim automatically" setting in Power Management; the main monitor does. STEPS TO REPRODUCE 1. Go to Power Management and set "Dim automatically" to 5 minutes 2. Wait 5 minutes OBSERVED RESULT The main monitor dims; the secondary monitor does not. EXPECTED RESULT Both monitors should dim. SOFTWARE/OS VERSIONS Linux/KDE Plasma: CachyOS KDE Plasma Version: 6.6.1 KDE Frameworks Version: 6.23 Qt Version: 6.10.2 ADDITIONAL INFORMATION Disabling and re-enabling the dim setting does not work.
Is the brightness of both monitors controllable in the System Tray "Brightness & Color" widget? Or do you only see one brightness slider, for the main monitor?
(In reply to Nate Graham from comment #1) > Is the brightness of both monitors controllable in the System Tray > "Brightness & Color" widget? Or do you only see one brightness slider, for > the main monitor? Both monitors are shown in the widget.
I can reproduce this on Plasma 6.6.1 On Plasma git-master, neither display is dimmed. They are turned off according to the power settings All displays show up in the brightness widgets on both systems
At first glance this doesn't seem like a ddcutil issue to me, but if there is I'd like to know the ddcutil version (CachyOS users are bleeding edge) and also relevant lines from "journalctl -t org_kde_powerdevil". The full segment would begin with "Starting libddcutil".
ddcutil 2.2.3 journalctl -t org_kde_powerdevil Mar 03 14:32:25 tracey-solus-aura org_kde_powerdevil[2651]: Starting libddcutil. library built Not set at Not set. stdout_stderr_redirected=true Mar 03 14:32:25 tracey-solus-aura org_kde_powerdevil[2651]: Initializing libddcutil. ddcutil version: 2.2.3, shared library: /usr/lib64/libddcutil.so.5.4.0 Mar 03 14:32:25 tracey-solus-aura org_kde_powerdevil[2651]: library built Not set at Not set. stdout_stderr_redirected=true Mar 03 14:32:25 tracey-solus-aura org_kde_powerdevil[2651]: [ 2651] Options passed from client: Mar 03 14:32:25 tracey-solus-aura org_kde_powerdevil[2651]: [ 2651] Applying combined libddcutil options: Mar 03 14:32:25 tracey-solus-aura org_kde_powerdevil[2651]: Library initialization complete. Mar 03 14:32:25 tracey-solus-aura org_kde_powerdevil[2651]: Watching for DPMS state changes unimplemented Mar 03 14:32:25 tracey-solus-aura org_kde_powerdevil[2651]: [ 2651] Watching for DPMS state changes unimplemented Mar 03 14:32:25 tracey-solus-aura org_kde_powerdevil[2651]: [ 2651] Watching for display connection changes, resolved watch mode = Watch_Mode_Udev, poll lo> Mar 03 14:32:25 tracey-solus-aura org_kde_powerdevil[2651]: [ 2651] extra_stabilization_millisec: 0, stabilizatio> Mar 03 14:32:25 tracey-solus-aura org_kde_powerdevil[2651]: [ 2651] libddcutil recheck thread 0x5613d3c8e350 started Mar 03 14:32:25 tracey-solus-aura org_kde_powerdevil[2651]: [ 2651] libddcutil watch thread 0x5613d3c8e2f0 started Mar 03 14:32:25 tracey-solus-aura org_kde_powerdevil[2651]: [ 2870] (dw_recheck_displays_func) Recheck interval: Sleeping for 200 milliseconds Mar 03 14:32:25 tracey-solus-aura org_kde_powerdevil[2651]: org.kde.powerdevil.chargethresholdhelper.getthreshold failed "Charge thresholds are not supporte> Mar 03 14:32:25 tracey-solus-aura org_kde_powerdevil[2651]: Handle button events action could not check for screen configuration Mar 03 14:32:25 tracey-solus-aura org_kde_powerdevil[2651]: org.kde.powerdevil.chargethresholdhelper.getthreshold failed "Charge thresholds are not supporte> Mar 03 14:32:26 tracey-solus-aura org_kde_powerdevil[2651]: Failed to register with host portal QDBusError("org.freedesktop.portal.Error.Failed", "Could not> Mar 03 14:32:26 tracey-solus-aura org_kde_powerdevil[2651]: Failed to register with host portal QDBusError("org.freedesktop.portal.Error.Failed", "Could not> Mar 03 14:33:21 tracey-solus-aura org_kde_powerdevil[4760]: Starting libddcutil. library built Not set at Not set. stdout_stderr_redirected=true Mar 03 14:33:21 tracey-solus-aura org_kde_powerdevil[4760]: Initializing libddcutil. ddcutil version: 2.2.3, shared library: /usr/lib64/libddcutil.so.5.4.0 Mar 03 14:33:21 tracey-solus-aura org_kde_powerdevil[4760]: library built Not set at Not set. stdout_stderr_redirected=true Mar 03 14:33:21 tracey-solus-aura org_kde_powerdevil[4760]: [ 4760] Options passed from client: Mar 03 14:33:21 tracey-solus-aura org_kde_powerdevil[4760]: [ 4760] Applying combined libddcutil options: Mar 03 14:33:22 tracey-solus-aura org_kde_powerdevil[4760]: Library initialization complete. Mar 03 14:33:22 tracey-solus-aura org_kde_powerdevil[4760]: Watching for DPMS state changes unimplemented Mar 03 14:33:22 tracey-solus-aura org_kde_powerdevil[4760]: [ 4760] Watching for DPMS state changes unimplemented Mar 03 14:33:22 tracey-solus-aura org_kde_powerdevil[4760]: [ 4760] Watching for display connection changes, resolved watch mode = Watch_Mode_Udev, poll lo> Mar 03 14:33:22 tracey-solus-aura org_kde_powerdevil[4760]: [ 4760] extra_stabilization_millisec: 0, stabilizatio> Mar 03 14:33:22 tracey-solus-aura org_kde_powerdevil[4760]: [ 4760] libddcutil recheck thread 0x55bc05044160 started Mar 03 14:33:22 tracey-solus-aura org_kde_powerdevil[4760]: [ 4760] libddcutil watch thread 0x55bc0503d660 started Mar 03 14:33:22 tracey-solus-aura org_kde_powerdevil[4760]: [ 4926] (dw_recheck_displays_func) Recheck interval: Sleeping for 200 milliseconds Mar 03 14:33:22 tracey-solus-aura org_kde_powerdevil[4760]: org.kde.powerdevil.chargethresholdhelper.getthreshold failed "Charge thresholds are not supporte> Mar 03 14:33:22 tracey-solus-aura org_kde_powerdevil[4760]: Handle button events action could not check for screen configuration Mar 03 14:33:22 tracey-solus-aura org_kde_powerdevil[4760]: org.kde.powerdevil.chargethresholdhelper.getthreshold failed "Charge thresholds are not supporte> Mar 03 14:33:22 tracey-solus-aura org_kde_powerdevil[4760]: Failed to register with host portal QDBusError("org.freedesktop.portal.Error.Failed", "Could not> Mar 03 14:33:22 tracey-solus-aura org_kde_powerdevil[4760]: Failed to register with host portal QDBusError("org.freedesktop.portal.Error.Failed", "Could not> Mar 03 14:43:44 tracey-solus-aura org_kde_powerdevil[2651]: [ 2871] Udev event detected Mar 03 14:43:45 tracey-solus-aura org_kde_powerdevil[2651]: [ 2871] Adding connected display with bus 15 Mar 03 14:43:45 tracey-solus-aura org_kde_powerdevil[2651]: [ 2871] Emitting DDCA_Display_Status_Event[680.362: DDCA_EVENT_DISPLAY_CONNECTED, card0-DP-1, > Mar 03 14:43:45 tracey-solus-aura org_kde_powerdevil[2651]: [ 2871] Starting 1 callback threads Mar 03 14:43:45 tracey-solus-aura org_kde_powerdevil[2651]: [ 2871] libddcutil callback thread 0x7f3ee0001fe0 started Mar 03 14:43:45 tracey-solus-aura org_kde_powerdevil[2651]: [ 2871] Started 1 event callback thread(s) Mar 03 14:43:45 tracey-solus-aura org_kde_powerdevil[2651]: [ 6767] Invoking callback function 0x7f3f11b51040 for event DDCA_Display_Status_Event[680.362: > Mar 03 14:43:45 tracey-solus-aura org_kde_powerdevil[2651]: [ 6767] Callback function 0x7f3f11b51040 for event DDCA_Display_Status_Event[680.362: DDCA_EVE> Mar 03 14:43:45 tracey-solus-aura org_kde_powerdevil[2651]: [ 2651] Quiescing libddcutil API... Mar 03 14:43:45 tracey-solus-aura org_kde_powerdevil[2651]: [ 2651] Quiesce libddcutil API complete Mar 03 14:43:45 tracey-solus-aura org_kde_powerdevil[2651]: [ 2651] Display redetection starting. Mar 03 14:43:45 tracey-solus-aura org_kde_powerdevil[2651]: [ 2870] recheck thread terminating because watch thread terminated Mar 03 14:43:46 tracey-solus-aura org_kde_powerdevil[2651]: [ 2651] Watch thread terminated. Mar 03 14:43:46 tracey-solus-aura org_kde_powerdevil[2651]: Error detecting VCP version using VCP feature xDF: Error_Info[DDCRC_RETRIES in ddc_write_read_wi> Mar 03 14:43:46 tracey-solus-aura org_kde_powerdevil[2651]: [ 2651] Error detecting VCP version using VCP feature xDF: Error_Info[DDCRC_RETRIES in ddc_writ> Mar 03 14:43:46 tracey-solus-aura org_kde_powerdevil[2651]: [ 2651] Watching for display connection changes, resolved watch mode = Watch_Mode_Udev, poll lo> Mar 03 14:43:46 tracey-solus-aura org_kde_powerdevil[2651]: [ 2651] extra_stabilization_millisec: 0, stabilizatio> Mar 03 14:43:46 tracey-solus-aura org_kde_powerdevil[2651]: [ 2651] libddcutil recheck thread 0x5613d3d9c790 started Mar 03 14:43:46 tracey-solus-aura org_kde_powerdevil[2651]: [ 6768] (dw_recheck_displays_func) Recheck interval: Sleeping for 200 milliseconds Mar 03 14:43:46 tracey-solus-aura org_kde_powerdevil[2651]: [ 2651] libddcutil watch thread 0x5613d3d9c280 started Mar 03 14:43:46 tracey-solus-aura org_kde_powerdevil[2651]: [ 2651] Display redetection finished. Mar 03 14:43:46 tracey-solus-aura org_kde_powerdevil[2651]: [ 2651] Unquiescing libddcutil API... Mar 03 15:30:28 tracey-solus-aura org_kde_powerdevil[2651]: org.kde.powerdevil.chargethresholdhelper.getthreshold failed "Charge thresholds are not supporte> Mar 03 15:48:00 tracey-solus-aura org_kde_powerdevil[2651]: org.kde.powerdevil.chargethresholdhelper.getthreshold failed "Charge thresholds are not supporte> Mar 03 15:49:36 tracey-solus-aura org_kde_powerdevil[2651]: org.kde.powerdevil.chargethresholdhelper.getthreshold failed "Charge thresholds are not supporte> Mar 03 15:49:49 tracey-solus-aura org_kde_powerdevil[2651]: org.kde.powerdevil.chargethresholdhelper.getthreshold failed "Charge thresholds are not supporte> Mar 03 19:59:33 tracey-solus-aura org_kde_powerdevil[2651]: Lid action was suppressed because an external monitor is present lines 1-63/63 (END)
(In reply to Sanfod Rockowitz from comment #4) > At first glance this doesn't seem like a ddcutil issue to me, but if there > is I'd like to know the ddcutil version (CachyOS users are bleeding edge) > and also relevant lines from "journalctl -t org_kde_powerdevil". The full > segment would begin with "Starting libddcutil". I am on ddcutil 2.2.5-2-1 from the CachyOS repo. Output from journalctl: mrt 04 17:17:44 phoenix org_kde_powerdevil[2169]: Starting libddcutil. library built Not set at Not set. stdout_stderr_redirected=true mrt 04 17:17:44 phoenix org_kde_powerdevil[2169]: Initializing libddcutil. ddcutil version: 2.2.5, shared library: /usr/lib/libddcutil.so.5.4.1 mrt 04 17:17:44 phoenix org_kde_powerdevil[2169]: library built Not set at Not set. stdout_stderr_redirected=true mrt 04 17:17:44 phoenix org_kde_powerdevil[2169]: [ 2169] Options passed from client: mrt 04 17:17:44 phoenix org_kde_powerdevil[2169]: [ 2169] Applying combined libddcutil options: mrt 04 17:17:45 phoenix org_kde_powerdevil[2169]: [ 2169] busno=7, Feature 0xdd should not exist but ddc_get_nontable_vcp_value() succeeds, returning mh=0x00 ml=0x01 sh=0x00 sl=0x01 mrt 04 17:17:46 phoenix org_kde_powerdevil[2169]: Library initialization complete. mrt 04 17:17:46 phoenix org_kde_powerdevil[2169]: Watching for DPMS state changes unimplemented mrt 04 17:17:46 phoenix org_kde_powerdevil[2169]: [ 2169] Watching for DPMS state changes unimplemented mrt 04 17:17:46 phoenix org_kde_powerdevil[2169]: [ 2169] Watching for display connection changes, resolved watch mode = Watch_Mode_Udev, poll loop interval = 500 millisec mrt 04 17:17:46 phoenix org_kde_powerdevil[2169]: [ 2169] extra_stabilization_millisec: 0, stabilization_poll_millisec: 100 mrt 04 17:17:46 phoenix org_kde_powerdevil[2169]: [ 2169] libddcutil recheck thread 0x55eb6e039910 started mrt 04 17:17:46 phoenix org_kde_powerdevil[2169]: [ 2169] libddcutil watch thread 0x55eb6e016e00 started mrt 04 17:17:46 phoenix org_kde_powerdevil[2169]: [ 2343] (dw_recheck_displays_func) Recheck interval: Sleeping for 200 milliseconds mrt 04 17:17:46 phoenix org_kde_powerdevil[2169]: org.kde.powerdevil.chargethresholdhelper.getthreshold failed "Charge thresholds are not supported by the kernel for this hardware" mrt 04 17:17:46 phoenix org_kde_powerdevil[2169]: org.kde.powerdevil.backlighthelper.brightness failed mrt 04 17:17:46 phoenix org_kde_powerdevil[2169]: Handle button events action could not check for screen configuration mrt 04 17:17:46 phoenix org_kde_powerdevil[2169]: org.kde.powerdevil.chargethresholdhelper.getthreshold failed "Charge thresholds are not supported by the kernel for this hardware" mrt 04 17:17:47 phoenix org_kde_powerdevil[2169]: Failed to register with host portal QDBusError("org.freedesktop.portal.Error.Failed", "Could not register app ID: App info not found for 'org.kde.org_kde_powerdevil'") mrt 04 17:17:47 phoenix org_kde_powerdevil[2169]: Failed to register with host portal QDBusError("org.freedesktop.portal.Error.Failed", "Could not register app ID: Connection already associated with an application ID")
The journalctl output of traceyc with ddcutil 2.2.3 and that of sayonarasidestep with ddcutil 2.2.5 give no indication that libddcutil is the locus of this bug. I do, however, note the following: Observations re traceyc output with ddcutil 2.2.3: : - libddcutil is started at 14;32;25 and then immediately after at 14:33:21, with no indication that powerdevil restarted. Seems odd to me. - The failure to read feature xDF VCP version is also odd. I'll spare everyone the complicated details. To say more I'd have to work with traceyc However, what's important here is that failure to obtain the VCP version is benign. It only affects how ddcutil interprets feature values (e.g. feature x10 is called "Brightness" vs "Luminesence" ) Observations re sayonarasidestep output with ddcutil 2.2.5: - Unlike the traceyc output, here's no UDEV event logged. The UDEV event detection code in 2.2.3 and that in 2.2.5 are identical. Do these logs really represent identical events? -
A possibly relevant merge request was started @ https://invent.kde.org/plasma/kwin/-/merge_requests/8944
Git commit a975425e2e1913d35a77164f4600c12fb55bf76c by Xaver Hugl. Committed on 06/03/2026 at 13:57. Pushed by zamundaaa into branch 'master'. backends/drm: fix check for ddc/ci software dimming We applied dimming on top of the brightness factor, but the brightness factor wasn't actually always applied. M +5 -4 src/backends/drm/drm_output.cpp https://invent.kde.org/plasma/kwin/-/commit/a975425e2e1913d35a77164f4600c12fb55bf76c
Git commit 66352b4211d441484820d08f952809c25de75353 by Vlad Zahorodnii, on behalf of Xaver Hugl. Committed on 06/03/2026 at 18:14. Pushed by vladz into branch 'Plasma/6.6'. backends/drm: fix check for ddc/ci software dimming We applied dimming on top of the brightness factor, but the brightness factor wasn't actually always applied. (cherry picked from commit a975425e2e1913d35a77164f4600c12fb55bf76c) Co-authored-by: Xaver Hugl <xaver.hugl@kde.org> M +5 -4 src/backends/drm/drm_output.cpp https://invent.kde.org/plasma/kwin/-/commit/66352b4211d441484820d08f952809c25de75353