https://bugs.kde.org/show_bug.cgi?id=516066
Bug ID: 516066
Summary: Brightness slider disappears after a few minutes of
uptime
Classification: Plasma
Product: plasmashell
Version First 6.5.5
Reported In:
Platform: CachyOS
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: Power management & brightness
Assignee: [email protected]
Reporter: [email protected]
Target Milestone: 1.0
Created attachment 189634
--> https://bugs.kde.org/attachment.cgi?id=189634&action=edit
Demonstration of the problem
SUMMARY
The brightness control slider for an external monitor (Philips 27M2N5500)
connected via DisplayPort (USB-C) is available immediately after boot but
consistently disappears from the system settings/tray after 2–5 minutes of
uptime.
STEPS TO REPRODUCE
1. Boot into CachyOS.
2. Confirm the brightness slider for the Philips 27M2N5500 is visible in the
UI.
3. Use the system normally for a few minutes.
4. Check the brightness control again.
OBSERVED RESULT
The slider for the external monitor disappears. The monitor is no longer
recognized as a dimmable device in the desktop environment.
EXPECTED RESULT
The brightness slider should remain available and functional throughout the
entire session.
SOFTWARE/OS VERSIONS
Operating System: CachyOS Linux
KDE Plasma Version: 6.5.5
KDE Frameworks Version: 6.23.0
Qt Version: 6.10.2
Kernel Version: 6.19.0-2-cachyos (64-bit)
Graphics Platform: Wayland
Processors: 12 × 11th Gen Intel® Core™ i5-11400H @ 2.70GHz
Memory: 16 ГиБ of RAM (15.3 ГиБ usable)
Graphics Processor 1: NVIDIA GeForce RTX 3060 Laptop GPU
Graphics Processor 2: Intel® UHD Graphics
Manufacturer: HP
Product Name: Victus by HP Laptop
ADDITIONAL INFORMATION
This behavior is unique to CachyOS. On Fedora, the slider remains stable and
functional.
Output of ddcutil detect after the slider disappears:
ddcutil detect
Invalid display
I2C bus: /dev/i2c-10
DRM_connector: card2-eDP-1
EDID synopsis:
Mfg id: BOE - BOE
Model:
Product code: 2733 (0x0aad)
Serial number: [REDACTED]
Binary serial number: [REDACTED]
Manufacture year: [REDACTED]
This is a laptop display. Laptop displays do not support DDC/CI.
Display 1
I2C bus: /dev/i2c-13
DRM_connector: card1-DP-2
EDID synopsis:
Mfg id: PHL - Philips Consumer Electronics Company
Model: 27M2N5500
Product code: 49976 (0xc338)
Serial number: [REDACTED]
Binary serial number: [REDACTED]
Manufacture year: [REDACTED]
VCP version: 2.2
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