evdi: harden software colour path and color_props advertisement - #2
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iDoMeteor merged 2 commits intoAug 15, 2026
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onetr1ck
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Apply only compositor GAMMA_LUT/CTM blobs (no gamma↔CTM synthesis). Which properties the CRTC advertises is selected at module load with color_props=both|gamma|ctm so Mutter can be steered like apple-drm (CTM-only) or gamma-only; reload the module to change it. Skip identity transforms, fuse diagonal CTMs into a 256-entry LUT for a cheap hot path, reuse a per-device GRABPIX scratch row, and full-dirty only when the effective apply payload changes so static Night Light updates still re-grab without spamming USB on no-op churn. Add a read-only color_status parameter for per-card apply path and scale dumps.
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Diagonal CTM fuse overwrote a compositor gamma LUT when both were set; compose CTM-then-gamma into the table instead. Shared GRABPIX scratch could be freed under concurrent grab — use a per-call buffer. DisplayLinkManager enables cursor events, so the SW tint path never ran and the pointer stayed day-white under Night Light. While colour is active, hide the HW cursor event and SW-blend with the same transform, re-advertising on colour change so DLM does not double-draw.
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Pushed another commit: fuse composes with an existing gamma LUT, GRABPIX uses a per-call scratch, and while colour is active we SW-blend the cursor and hide the HW cursor event so DisplayLinkManager does not leave it untinted. For DisplayLink DisplayLink#584, worth linking DisplayLink#44 (gamma ramp, open since 2016) if you have not already — that looks like the long-standing issue this closes. |
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Based on your colour management branch (after the earlier damage/cursor/color_props work).
This keeps applying only real compositor GAMMA_LUT and CTM blobs, with no gamma↔CTM synthesis. color_props=both|gamma|ctm at module load chooses which DRM properties the CRTC advertises so Mutter can be steered like apple-drm (CTM only) or gamma only; reload the module to change it.
Identity transforms are skipped, diagonal CTMs fuse into a 256-entry LUT (composing with an existing gamma when both are set), GRABPIX uses a per-call scratch row, and full-dirty runs only when the effective apply payload changes. While colour is active, the software cursor path is forced so DisplayLinkManager cursor events do not leave an untinted pointer. color_status dumps the per-card apply path.
Tested on a DisplayLink dock with GNOME Night Light (color_props=ctm). Happy for you to take any of this into the upstream PR or leave it. DisplayLink#44 is still the long-standing gamma ramp request if you want a Closes link on DisplayLink#584.