https://bugs.kde.org/show_bug.cgi?id=524776
Bug ID: 524776
Summary: Title: Plasma Login Manager (plasmalogin) fails to
detect outputs on dual-connector/MST monitor despite
valid EDID and existing kwinoutputconfig.json
Classification: Plasma
Product: plasma-login-manager
Version First 6.7.4
Reported In:
Platform: Other
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: general
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected], [email protected]
Target Milestone: ---
Title: Plasma Login Manager (plasmalogin) fails to detect outputs on
dual-connector/MST monitor despite valid EDID and existing
kwinoutputconfig.json
Environment:
Fedora 44 (kernel 7.1.8 and 7.1.9 both affected — not kernel-specific)
KDE Plasma with Plasma Login Manager (plasmalogin), replacing SDDM as default
GPU: Nvidia RTX 2060 (TU104), proprietary driver 610.57.04, Secure Boot enabled
with correctly signed/enrolled akmod
Intel iGPU (Coffee Lake) also present, no display connected
Monitor: Dell (2560×1600), connected via two DisplayPort connectors (DP-7,
DP-8) — appears to be MST/tiled configuration
Symptom:
On boot, plasma-login-kwin_wayland starts cleanly with no errors, successfully
opens /dev/dri/card2 (confirmed via fuser), but logs "There are no outputs -
creating placeholder screen" for the greeter, wallpaper, keyboard, and
activity-manager components. Result: black screen with only a visible cursor at
the login screen. No further errors are logged.
What's confirmed NOT the cause:
Driver loading/signing: nvidia-smi works correctly in a real user session with
the same driver
Permissions: getfacl confirms plasmalogin user has rw ACL on /dev/dri/card2
Device targeting: with KWIN_DRM_DEVICES=/dev/dri/card2:/dev/dri/card1 set, KWin
correctly opens card2 with no errors
Boot-order race: added a systemd device-unit dependency (Wants=/After= on the
tagged dev-dri-by-path-pci-...card.device unit) forcing plasmalogin.service to
wait for the Nvidia DRM device before starting — device opens immediately and
cleanly, but outputs still aren't detected
EDID: both card2-DP-7/edid and card2-DP-8/edid read 256 bytes successfully
Kernel version: identical failure on both 7.1.8 and 7.1.9
Existing config: /var/lib/plasmalogin/.config/kwinoutputconfig.json contains a
valid, previously-generated dual-output layout for this exact monitor (both
connectors, correct resolution/position)
Workaround: Switching to SDDM as the display manager resolves the issue
completely with identical hardware/driver/monitor configuration — SDDM's
Wayland greeter detects and uses both outputs correctly.
Suspected cause: Output enumeration failure specific to
plasma-login-kwin_wayland (the login-manager variant of KWin) with a
dual-connector/MST-style monitor setup, since the regular user-session KWin has
no problem with the same hardware.
--
You are receiving this mail because:
You are watching all bug changes.
