https://bugs.kde.org/show_bug.cgi?id=528310
Bug ID: 528310
Summary: [Wayland/DRM] eDP panel marked HDR incapable due to
CTA-861 block nested in DisplayID 2.0 container
Classification: Plasma
Product: kwin
Version First 6.8.2
Reported In:
Platform: Fedora RPMs
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: colour-management
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
Target Milestone: ---
Created attachment 198038
--> https://bugs.kde.org/attachment.cgi?id=198038&action=edit
edid-decode output of unmodified factory EDID showing DisplayID 2.0 CTA block
SUMMARY
On Wayland, KWin marks an HDR-capable internal OLED panel (Samsung ATNA40CU05-0
on an ASUS ROG Zephyrus G14) as "HDR: incapable" via kscreen-doctor.
ROOT CAUSE
The panel's raw EDID does not expose a standalone top-level CTA-861 Extension
Block (Tag 0x02). Instead, it uses a DisplayID 2.0 Extension Block (Tag 0x70)
that contains a nested "CTA-861 DisplayID Data Block".
This nested block defines the HDR Static Metadata (SMPTE ST 2084 / PQ, 616
cd/m² peak, Static Metadata Type 1) and BT.2020 colorimetry.
KWin's EDID parsing logic does not traverse CTA-861 blocks nested inside
DisplayID 2.0 containers on eDP connectors, causing it to conclude the display
has no HDR capability.
STEPS TO REPRODUCE
1. Run a Plasma 6 Wayland session on a laptop equipped with a Samsung
ATNA40CU05-0 OLED panel.
2. Check output state with `kscreen-doctor -o`.
3. Observe HDR capability under eDP-1.
OBSERVED RESULT
kscreen-doctor reports:
HDR: incapable
EXPECTED RESULT
KWin's EDID parser should inspect CTA-861 data blocks inside DisplayID 2.0
containers so the panel is recognized as HDR-capable.
WORKAROUND / VERIFICATION
Synthesizing an EDID override where the CTA-861 data block is relocated to a
standard top-level CTA-861 extension block (Tag 0x02) and loaded via the kernel
parameter `drm.edid_firmware=eDP-1:...` immediately resolves the issue. Upon
rebooting with the top-level block, KWin detects HDR capabilities, sets HDR:
enabled, and pushes non-zero HDR_OUTPUT_METADATA blobs to amdgpu.
SOFTWARE / HARDWARE VERSIONS
OS: Fedora Linux 45
KDE Plasma Version: 6.8.2
KWin Version: 6.8.2
Graphics Platform: Wayland
Kernel: 7.2.15
GPU: AMD Radeon 780M (amdgpu)
Panel: Samsung SDC ATNA40CU05-0
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