https://bugs.kde.org/show_bug.cgi?id=518271
Bug ID: 518271
Summary: After external HDMI monitor is turned off, its input
auto-select causes the screen to come back on
Classification: I don't know
Product: kde
Version First unspecified
Reported In:
Platform: CachyOS
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: general
Assignee: [email protected]
Reporter: [email protected]
Target Milestone: ---
SUMMARY
HDMI-connected external monitor automatically comes back on a few seconds after
being disabled.
STEPS TO REPRODUCE
1. Connect an external monitor via HDMI (the monitor must have an auto-input
select feature that cannot be disabled)
2. Turn the screen off (through idle settings or a command such as
kscreen-doctor --dpms off
3. Wait 5 to 10 seconds
OBSERVED RESULT
A few seconds after the monitor is turned off, some models (including mine)
will cycle through all available inputs. When the HDMI connection is tried
again, this is treated as some kind of monitor hotplug event by KDE, causing
the laptop screen to come on briefly and then causing the external monitor to
come back on permanently. (Because of the smaller screen briefly turning on,
some applications such as Steam also end up with zoom/placement issues.)
EXPECTED RESULT
Both screens remain off (until enabled again through some intentional method).
SOFTWARE/OS VERSIONS
Operating System: CachyOS Linux
KDE Plasma Version: 6.6.3
KDE Frameworks Version: 6.24.0
Qt Version: 6.11.0
Kernel Version: 6.19.10-1-cachyos (64-bit)
Graphics Platform: Wayland
Processors: 16 × AMD Ryzen 7 7735U with Radeon Graphics
Memory: 32 GiB of RAM (30.7 GiB usable)
Graphics Processor: AMD Radeon Graphics
ADDITIONAL INFORMATION
This was working perfectly with the same hardware & DE setup (on CachyOS with
KDE Plasma) for months, up until a software update 1 or 2 months ago that
included a number of different application updates.
This is a known issue that has been reported elsewhere over the past few years,
including this other bug report that seems to have been fixed in Plasma 6.6.2:
https://bugs.kde.org/show_bug.cgi?id=516454
https://forum.level1techs.com/t/wayland-monitor-wont-stay-off/204261
I have tried a few possible solutions I've found online, but none have worked.
The issue does not occur when connected via USB-C, but for unrelated reasons I
need to be connected via HDMI.
The issue seems to have some relationship to the Linux kernel version, because
it briefly went away again when switching from the most recent CachyOS kernel
6.19 to the LTS 6.18.X ... however, since a further software update, the issue
now persists no matter which kernel version I am on.
Strangely, I tried the Niri DE with the same kernel & hardware, and the problem
does *not* occur (i.e. the monitor is table to turn off after an idle period
without turning back on again). This would seem to indicate that kscreen or
something else KDE-related could handle the event properly, no matter what
kernel is active.
My monitor (Lenovo Q27h-10) has not received any firmware updates in many
years, and there is no way to disable the auto-input select feature.
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