From f10dd1da1c7b58bd1dde79e18c70109e3f90c3d4 Mon Sep 17 00:00:00 2001
From: Simon Ser <contact@emersion.fr>
Date: Sat, 24 May 2025 13:40:05 +0200
Subject: [PATCH] backend/drm: add support for color transforms

---
 backend/drm/atomic.c | 19 +++++++++++++------
 backend/drm/drm.c    | 12 ++++++++++--
 backend/drm/legacy.c | 15 ++++++++++++---
 3 files changed, 35 insertions(+), 11 deletions(-)

diff --git a/backend/drm/atomic.c b/backend/drm/atomic.c
index 037c3c23a..cfef2ff36 100644
--- a/backend/drm/atomic.c
+++ b/backend/drm/atomic.c
@@ -10,6 +10,7 @@
 #include "backend/drm/fb.h"
 #include "backend/drm/iface.h"
 #include "backend/drm/util.h"
+#include "render/color.h"
 
 static char *atomic_commit_flags_str(uint32_t flags) {
 	const char *const l[] = {
@@ -251,19 +252,25 @@ bool drm_atomic_connector_prepare(struct wlr_drm_connector_state *state, bool mo
 	}
 
 	uint32_t gamma_lut = crtc->gamma_lut;
-	if (state->base->committed & WLR_OUTPUT_STATE_GAMMA_LUT) {
+	if (state->base->committed & WLR_OUTPUT_STATE_COLOR_TRANSFORM) {
+		size_t dim = 0;
+		uint16_t *lut = NULL;
+		if (state->base->color_transform != NULL) {
+			struct wlr_color_transform_lut_3x1d *tr =
+				color_transform_lut_3x1d_from_base(state->base->color_transform);
+			dim = tr->dim;
+			lut = tr->lut_3x1d;
+		}
+
 		// Fallback to legacy gamma interface when gamma properties are not
 		// available (can happen on older Intel GPUs that support gamma but not
 		// degamma).
 		if (crtc->props.gamma_lut == 0) {
-			if (!drm_legacy_crtc_set_gamma(drm, crtc,
-					state->base->gamma_lut_size,
-					state->base->gamma_lut)) {
+			if (!drm_legacy_crtc_set_gamma(drm, crtc, dim, lut)) {
 				return false;
 			}
 		} else {
-			if (!create_gamma_lut_blob(drm, state->base->gamma_lut_size,
-					state->base->gamma_lut, &gamma_lut)) {
+			if (!create_gamma_lut_blob(drm, dim, lut, &gamma_lut)) {
 				return false;
 			}
 		}
diff --git a/backend/drm/drm.c b/backend/drm/drm.c
index e9e4c6db2..653497813 100644
--- a/backend/drm/drm.c
+++ b/backend/drm/drm.c
@@ -24,6 +24,7 @@
 #include "backend/drm/fb.h"
 #include "backend/drm/iface.h"
 #include "backend/drm/util.h"
+#include "render/color.h"
 #include "types/wlr_output.h"
 #include "util/env.h"
 #include "config.h"
@@ -37,11 +38,11 @@ static const uint32_t COMMIT_OUTPUT_STATE =
 	WLR_OUTPUT_STATE_BUFFER |
 	WLR_OUTPUT_STATE_MODE |
 	WLR_OUTPUT_STATE_ENABLED |
-	WLR_OUTPUT_STATE_GAMMA_LUT |
 	WLR_OUTPUT_STATE_ADAPTIVE_SYNC_ENABLED |
 	WLR_OUTPUT_STATE_LAYERS |
 	WLR_OUTPUT_STATE_WAIT_TIMELINE |
-	WLR_OUTPUT_STATE_SIGNAL_TIMELINE;
+	WLR_OUTPUT_STATE_SIGNAL_TIMELINE |
+	WLR_OUTPUT_STATE_COLOR_TRANSFORM;
 
 static const uint32_t SUPPORTED_OUTPUT_STATE =
 	WLR_OUTPUT_STATE_BACKEND_OPTIONAL | COMMIT_OUTPUT_STATE;
@@ -856,6 +857,13 @@ static bool drm_connector_prepare(struct wlr_drm_connector_state *conn_state, bo
 		}
 	}
 
+	if ((state->committed & WLR_OUTPUT_STATE_COLOR_TRANSFORM) && state->color_transform != NULL &&
+			state->color_transform->type != COLOR_TRANSFORM_LUT_3X1D) {
+		wlr_drm_conn_log(conn, WLR_DEBUG,
+			"Only 3x1D LUT color transforms are supported");
+		return false;
+	}
+
 	if (test_only && conn->backend->mgpu_renderer.wlr_rend) {
 		// If we're running as a secondary GPU, we can't perform an atomic
 		// commit without blitting a buffer.
diff --git a/backend/drm/legacy.c b/backend/drm/legacy.c
index d77c9d342..223852ec1 100644
--- a/backend/drm/legacy.c
+++ b/backend/drm/legacy.c
@@ -7,6 +7,7 @@
 #include "backend/drm/fb.h"
 #include "backend/drm/iface.h"
 #include "backend/drm/util.h"
+#include "render/color.h"
 #include "types/wlr_output.h"
 
 static bool legacy_fb_props_match(struct wlr_drm_fb *fb1,
@@ -124,9 +125,17 @@ static bool legacy_crtc_commit(const struct wlr_drm_connector_state *state,
 		}
 	}
 
-	if (state->base->committed & WLR_OUTPUT_STATE_GAMMA_LUT) {
-		if (!drm_legacy_crtc_set_gamma(drm, crtc,
-				state->base->gamma_lut_size, state->base->gamma_lut)) {
+	if (state->base->committed & WLR_OUTPUT_STATE_COLOR_TRANSFORM) {
+		size_t dim = 0;
+		uint16_t *lut = NULL;
+		if (state->base->color_transform != NULL) {
+			struct wlr_color_transform_lut_3x1d *tr =
+				color_transform_lut_3x1d_from_base(state->base->color_transform);
+			dim = tr->dim;
+			lut = tr->lut_3x1d;
+		}
+
+		if (!drm_legacy_crtc_set_gamma(drm, crtc, dim, lut)) {
 			return false;
 		}
 	}