https://bugs.kde.org/show_bug.cgi?id=492641
Bug ID: 492641
Summary: Monitor not detected by sddm if connected after boot
but before login
Classification: Plasma
Product: kwin
Version: 6.1.4
Platform: openSUSE
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: general
Assignee: [email protected]
Reporter: [email protected]
Target Milestone: ---
SUMMARY
In my simple, single 1080p monitor setup, connected via HDMI, if the monitor is
first connected after sddm has already started (presumably) and the login
screen has been reached, the monitor is not detected and the PC continues to
output no signal.
STEPS TO REPRODUCE
1. Disconnect monitor cable from output port on PC
2. Power on PC, wait until fan activity has died down or other indicator that
boot process is complete and sddm should have been started
3. Reconnect monitor to PC
4. Observe no change
OBSERVED RESULT
Behaviour in different scenarios:
1. If the monitor is connected and on at boot, the sddm login screen displays
fine and everything is ok.
2. If the monitor is connected and *off* at boot, but the monitor is then
turned on, the monitor is detected and the login screen appears.
3. If the monitor is disconnected/switched off *while logged into a desktop
Plasma session*, then reconnected/switched back on, the monitor is detected and
everything reappears just fine.
4. If the monitor is *not connected at boot*, then connected before/at login,
nothing is detected and nothing appears on screen; the monitor indicates that
it is receiving no signal.
The results of trying different things after reaching case 4:
4a. If it is simply assumed that, even though it is not being displayed, the
sddm login screen is indeed the current one, and an attempt is made to log in
by typing the user password and pressing enter, the monitor is brought to life;
however, it is the sddm login screen that appears, with an empty password
field, not the Plasma desktop, as if sddm was simply restarted.
4b. Switching to an alternative tty using Ctrl+Alt+F4 etc. works fine, and from
there sddm can simply be restarted using e.g. `sudo systemctl restart
sddm.service`, at which point the login screen appears.
4c. Changing the input on the monitor to VGA and back to HDMI changes nothing.
EXPECTED RESULT
Attaching a new monitor should be successfully detected and displayed in the
same way pre-login (by sddm) as is done mid-boot (not sure what by) and
post-login (by Plasma shell presumably).
SOFTWARE/OS VERSIONS
Linux/KDE Plasma: OpenSUSE Tumbleweed 20240829
Kernel: 6.10.5
KDE Plasma Version: 6.1.4
KDE Frameworks Version: 6.5.0
Qt Version: 6.7.2
ADDITIONAL INFORMATION
- Inspecting `/etc/sddm.conf` and `/etc/sddm.conf.d/kde_settings.conf` seems to
indicate that sddm is running on the default X11 not Wayland (by absence of
anything described at https://bbs.archlinux.org/viewtopic.php?id=289612) but
Plasma is running under Wayland on my system.
- Display output is via HDMI from the GPU, which is an AMD Ryzen RX 6600.
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