backend/drm: add support for CTM

backend/drm/atomic.c

@@ -154,6 +154,31 @@ static bool create_gamma_lut_blob(struct wlr_drm_backend *drm,
 	return true;
 }
 
+static bool create_ctm_blob(struct wlr_drm_backend *drm,
+		const float *matrix, uint32_t *blob_id) {
+	if (matrix == NULL) {
+		*blob_id = 0;
+		return true;
+	}
+
+	// Convert to S31.32 sign-magnitude fixed floating-point encoding
+	struct drm_color_ctm ctm = {0};
+	for (size_t i = 0; i < 9; i++) {
+		uint64_t v = fabs(matrix[i]) * ((uint64_t)1 << 32);
+		if (matrix[i] < 0) {
+			v |= (uint64_t)1 << 63;
+		}
+		ctm.matrix[i] = v;
+	}
+
+	if (drmModeCreatePropertyBlob(drm->fd, &ctm, sizeof(ctm), blob_id) != 0) {
+		wlr_log_errno(WLR_ERROR, "Unable to create CTM property blob");
+		return false;
+	}
+
+	return true;
+}
+
 bool create_fb_damage_clips_blob(struct wlr_drm_backend *drm,
 		int width, int height, const pixman_region32_t *damage, uint32_t *blob_id) {
 	pixman_region32_t clipped;
@@ -332,26 +357,39 @@ bool drm_atomic_connector_prepare(struct wlr_drm_connector_state *state, bool mo
 	}
 
 	uint32_t gamma_lut = crtc->gamma_lut;
+	uint32_t ctm = crtc->ctm;
 	if (state->base->committed & WLR_OUTPUT_STATE_COLOR_TRANSFORM) {
-		size_t dim = 0;
+		size_t lut_dim = 0;
 		uint16_t *lut = NULL;
+		const float *matrix = NULL;
 		if (state->crtc_color_transform != NULL) {
-			dim = state->crtc_color_transform->lut_3x1d->dim;
+			lut_dim = state->crtc_color_transform->lut_3x1d->dim;
 			lut = state->crtc_color_transform->lut_3x1d->lut_3x1d;
+			if (state->crtc_color_transform->has_matrix) {
+				matrix = state->crtc_color_transform->matrix;
+			}
 		}
 
 		// 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, dim, lut)) {
+			if (!drm_legacy_crtc_set_gamma(drm, crtc, lut_dim, lut)) {
 				return false;
 			}
 		} else {
-			if (!create_gamma_lut_blob(drm, dim, lut, &gamma_lut)) {
+			if (!create_gamma_lut_blob(drm, lut_dim, lut, &gamma_lut)) {
 				return false;
 			}
 		}
+
+		if (matrix != NULL && crtc->props.ctm == 0) {
+			wlr_log(WLR_DEBUG, "CRTC %"PRIu32" doesn't support CTM", crtc->id);
+			return false;
+		}
+		if (!create_ctm_blob(drm, matrix, &ctm)) {
+			return false;
+		}
 	}
 
 	uint32_t fb_damage_clips = 0;
@@ -394,6 +432,7 @@ bool drm_atomic_connector_prepare(struct wlr_drm_connector_state *state, bool mo
 
 	state->mode_id = mode_id;
 	state->gamma_lut = gamma_lut;
+	state->ctm = ctm;
 	state->fb_damage_clips = fb_damage_clips;
 	state->primary_in_fence_fd = in_fence_fd;
 	state->vrr_enabled = vrr_enabled;
@@ -413,6 +452,7 @@ void drm_atomic_connector_apply_commit(struct wlr_drm_connector_state *state) {
 	crtc->own_mode_id = true;
 	commit_blob(drm, &crtc->mode_id, state->mode_id);
 	commit_blob(drm, &crtc->gamma_lut, state->gamma_lut);
+	commit_blob(drm, &crtc->ctm, state->ctm);
 	commit_blob(drm, &conn->hdr_output_metadata, state->hdr_output_metadata);
 
 	conn->output.adaptive_sync_status = state->vrr_enabled ?
@@ -439,6 +479,7 @@ void drm_atomic_connector_rollback_commit(struct wlr_drm_connector_state *state)
 
 	rollback_blob(drm, &crtc->mode_id, state->mode_id);
 	rollback_blob(drm, &crtc->gamma_lut, state->gamma_lut);
+	rollback_blob(drm, &crtc->ctm, state->ctm);
 	rollback_blob(drm, &conn->hdr_output_metadata, state->hdr_output_metadata);
 
 	destroy_blob(drm, state->fb_damage_clips);
@@ -543,6 +584,9 @@ static void atomic_connector_add(struct atomic *atom,
 		if (crtc->props.gamma_lut != 0) {
 			atomic_add(atom, crtc->id, crtc->props.gamma_lut, state->gamma_lut);
 		}
+		if (crtc->props.ctm != 0) {
+			atomic_add(atom, crtc->id, crtc->props.ctm, state->ctm);
+		}
 		if (crtc->props.vrr_enabled != 0) {
 			atomic_add(atom, crtc->id, crtc->props.vrr_enabled, state->vrr_enabled);
 		}

backend/drm/color.c

@@ -3,6 +3,12 @@
 #include "backend/drm/color.h"
 #include "backend/drm/drm.h"
 #include "render/color.h"
+#include "util/matrix.h"
+
+enum wlr_drm_crtc_color_transform_stage {
+	WLR_DRM_CRTC_COLOR_TRANSFORM_MATRIX,
+	WLR_DRM_CRTC_COLOR_TRANSFORM_LUT_3X1D,
+};
 
 static struct wlr_color_transform_lut_3x1d *create_identity_3x1dlut(size_t dim) {
 	if (dim == 0) {
@@ -21,8 +27,21 @@ static struct wlr_color_transform_lut_3x1d *create_identity_3x1dlut(size_t dim)
 	return color_transform_lut_3x1d_from_base(out);
 }
 
+static bool set_stage(enum wlr_drm_crtc_color_transform_stage *current,
+		enum wlr_drm_crtc_color_transform_stage next) {
+	// Enforce that we fill the pipeline in order: first CTM then GAMMA_LUT
+	if (*current > next) {
+		return false;
+	}
+	*current = next;
+	return true;
+}
+
 static bool drm_crtc_color_transform_init_lut_3x1d(struct wlr_drm_crtc_color_transform *out,
-		size_t dim) {
+		enum wlr_drm_crtc_color_transform_stage *stage, size_t dim) {
+	if (!set_stage(stage, WLR_DRM_CRTC_COLOR_TRANSFORM_LUT_3X1D)) {
+		return false;
+	}
 	if (out->lut_3x1d != NULL) {
 		return true;
 	}
@@ -31,13 +50,14 @@ static bool drm_crtc_color_transform_init_lut_3x1d(struct wlr_drm_crtc_color_tra
 }
 
 static bool drm_crtc_color_transform_convert(struct wlr_drm_crtc_color_transform *out,
-		struct wlr_color_transform *in, size_t lut_3x1d_dim) {
+		struct wlr_color_transform *in, enum wlr_drm_crtc_color_transform_stage *stage,
+		size_t lut_3x1d_dim) {
 	switch (in->type) {
 	case COLOR_TRANSFORM_INVERSE_EOTF:;
 		struct wlr_color_transform_inverse_eotf *inv_eotf =
 			wlr_color_transform_inverse_eotf_from_base(in);
 
-		if (!drm_crtc_color_transform_init_lut_3x1d(out, lut_3x1d_dim)) {
+		if (!drm_crtc_color_transform_init_lut_3x1d(out, stage, lut_3x1d_dim)) {
 			return false;
 		}
 
@@ -58,7 +78,7 @@ static bool drm_crtc_color_transform_convert(struct wlr_drm_crtc_color_transform
 			return false;
 		}
 
-		if (!drm_crtc_color_transform_init_lut_3x1d(out, lut_3x1d_dim)) {
+		if (!drm_crtc_color_transform_init_lut_3x1d(out, stage, lut_3x1d_dim)) {
 			return false;
 		}
 
@@ -68,15 +88,21 @@ static bool drm_crtc_color_transform_convert(struct wlr_drm_crtc_color_transform
 		}
 
 		return true;
-	case COLOR_TRANSFORM_MATRIX:
-		return false; // TODO: add support for CTM
+	case COLOR_TRANSFORM_MATRIX:;
+		struct wlr_color_transform_matrix *matrix = wl_container_of(in, matrix, base);
+		if (!set_stage(stage, WLR_DRM_CRTC_COLOR_TRANSFORM_MATRIX)) {
+			return false;
+		}
+		wlr_matrix_multiply(out->matrix, matrix->matrix, out->matrix);
+		out->has_matrix = true;
+		return true;
 	case COLOR_TRANSFORM_LCMS2:
 		return false; // unsupported
 	case COLOR_TRANSFORM_PIPELINE:;
 		struct wlr_color_transform_pipeline *pipeline = wl_container_of(in, pipeline, base);
 
 		for (size_t i = 0; i < pipeline->len; i++) {
-			if (!drm_crtc_color_transform_convert(out, pipeline->transforms[i], lut_3x1d_dim)) {
+			if (!drm_crtc_color_transform_convert(out, pipeline->transforms[i], stage, lut_3x1d_dim)) {
 				return false;
 			}
 		}
@@ -109,9 +135,11 @@ static struct wlr_drm_crtc_color_transform *drm_crtc_color_transform_create(
 
 	tr->base = base;
 	wlr_addon_init(&tr->addon, &base->addons, crtc, &addon_impl);
+	wlr_matrix_identity(tr->matrix);
 
 	size_t lut_3x1d_dim = drm_crtc_get_gamma_lut_size(backend, crtc);
-	tr->failed = !drm_crtc_color_transform_convert(tr, base, lut_3x1d_dim);
+	enum wlr_drm_crtc_color_transform_stage stage = WLR_DRM_CRTC_COLOR_TRANSFORM_MATRIX;
+	tr->failed = !drm_crtc_color_transform_convert(tr, base, &stage, lut_3x1d_dim);
 
 	return tr;
 }

backend/drm/drm.c

@@ -391,6 +391,9 @@ void finish_drm_resources(struct wlr_drm_backend *drm) {
 		if (crtc->gamma_lut) {
 			drmModeDestroyPropertyBlob(drm->fd, crtc->gamma_lut);
 		}
+		if (crtc->ctm) {
+			drmModeDestroyPropertyBlob(drm->fd, crtc->ctm);
+		}
 	}
 
 	free(drm->crtcs);

backend/drm/libliftoff.c

@@ -328,6 +328,9 @@ static bool add_connector(drmModeAtomicReq *req,
 		if (crtc->props.gamma_lut != 0) {
 			ok = ok && add_prop(req, crtc->id, crtc->props.gamma_lut, state->gamma_lut);
 		}
+		if (crtc->props.ctm != 0) {
+			ok = ok && add_prop(req, crtc->id, crtc->props.ctm, state->ctm);
+		}
 		if (crtc->props.vrr_enabled != 0) {
 			ok = ok && add_prop(req, crtc->id, crtc->props.vrr_enabled, state->vrr_enabled);
 		}

backend/drm/properties.c

@@ -40,6 +40,7 @@ static const struct prop_info connector_info[] = {
 static const struct prop_info crtc_info[] = {
 #define INDEX(name) (offsetof(struct wlr_drm_crtc_props, name) / sizeof(uint32_t))
 	{ "ACTIVE", INDEX(active) },
+	{ "CTM", INDEX(ctm) },
 	{ "GAMMA_LUT", INDEX(gamma_lut) },
 	{ "GAMMA_LUT_SIZE", INDEX(gamma_lut_size) },
 	{ "MODE_ID", INDEX(mode_id) },

include/backend/drm/color.h

@@ -12,6 +12,8 @@ struct wlr_drm_crtc_color_transform {
 	struct wlr_addon addon; // wlr_color_transform.addons
 	bool failed;
 	struct wlr_color_transform_lut_3x1d *lut_3x1d;
+	float matrix[9];
+	bool has_matrix;
 };
 
 struct wlr_drm_crtc_color_transform *drm_crtc_color_transform_import(

include/backend/drm/drm.h

@@ -76,6 +76,7 @@ struct wlr_drm_crtc {
 	bool own_mode_id;
 	uint32_t mode_id;
 	uint32_t gamma_lut;
+	uint32_t ctm;
 
 	// Legacy only
 	int legacy_gamma_size;
@@ -159,6 +160,7 @@ struct wlr_drm_connector_state {
 	// used by atomic
 	uint32_t mode_id;
 	uint32_t gamma_lut;
+	uint32_t ctm;
 	uint32_t fb_damage_clips;
 	int primary_in_fence_fd, out_fence_fd;
 	bool vrr_enabled;

include/backend/drm/properties.h

@@ -35,6 +35,7 @@ struct wlr_drm_crtc_props {
 	uint32_t vrr_enabled;
 	uint32_t gamma_lut;
 	uint32_t gamma_lut_size;
+	uint32_t ctm;
 
 	// atomic-modesetting only