backend/drm: apply gamma LUT on page-flip

backend/drm/atomic.c

@@ -69,6 +69,41 @@ static void atomic_add(struct atomic *atom, uint32_t id, uint32_t prop, uint64_t
 	}
 }
 
+static bool create_gamma_lut_blob(struct wlr_drm_backend *drm,
+		struct wlr_drm_crtc *crtc, uint32_t *blob_id) {
+	if (crtc->gamma_table_size == 0) {
+		*blob_id = 0;
+		return true;
+	}
+
+	uint32_t size = crtc->gamma_table_size;
+	uint16_t *r = crtc->gamma_table;
+	uint16_t *g = crtc->gamma_table + size;
+	uint16_t *b = crtc->gamma_table + 2 * size;
+
+	struct drm_color_lut *gamma = malloc(size * sizeof(struct drm_color_lut));
+	if (gamma == NULL) {
+		wlr_log(WLR_ERROR, "Failed to allocate gamma table");
+		return false;
+	}
+
+	for (size_t i = 0; i < size; i++) {
+		gamma[i].red = r[i];
+		gamma[i].green = g[i];
+		gamma[i].blue = b[i];
+	}
+
+	if (drmModeCreatePropertyBlob(drm->fd, gamma,
+			size * sizeof(struct drm_color_lut), blob_id) != 0) {
+		wlr_log_errno(WLR_ERROR, "Unable to create property blob");
+		free(gamma);
+		return false;
+	}
+	free(gamma);
+
+	return true;
+}
+
 static void plane_disable(struct atomic *atom, struct wlr_drm_plane *plane) {
 	uint32_t id = plane->id;
 	const union wlr_drm_plane_props *props = &plane->props;
@@ -126,6 +161,24 @@ static bool atomic_crtc_pageflip(struct wlr_drm_backend *drm,
 		}
 	}
 
+	if (crtc->pending & WLR_DRM_CRTC_GAMMA_LUT) {
+		// 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)) {
+				return false;
+			}
+		} else {
+			if (crtc->gamma_lut != 0) {
+				drmModeDestroyPropertyBlob(drm->fd, crtc->gamma_lut);
+			}
+
+			if (!create_gamma_lut_blob(drm, crtc, &crtc->gamma_lut)) {
+				return false;
+			}
+		}
+	}
+
 	uint32_t flags = DRM_MODE_PAGE_FLIP_EVENT;
 	if (modeset) {
 		flags |= DRM_MODE_ATOMIC_ALLOW_MODESET;
@@ -142,6 +195,7 @@ static bool atomic_crtc_pageflip(struct wlr_drm_backend *drm,
 	}
 	atomic_add(&atom, crtc->id, crtc->props.mode_id, crtc->mode_id);
 	atomic_add(&atom, crtc->id, crtc->props.active, 1);
+	atomic_add(&atom, crtc->id, crtc->props.gamma_lut, crtc->gamma_lut);
 	set_plane_props(&atom, drm, crtc->primary, crtc->id, 0, 0);
 	if (crtc->cursor) {
 		if (crtc->cursor->cursor_enabled) {
@@ -195,45 +249,6 @@ static bool atomic_crtc_set_cursor(struct wlr_drm_backend *drm,
 	return true;
 }
 
-static bool atomic_crtc_set_gamma(struct wlr_drm_backend *drm,
-		struct wlr_drm_crtc *crtc, size_t size,
-		uint16_t *r, uint16_t *g, uint16_t *b) {
-	// 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) {
-		return legacy_iface.crtc_set_gamma(drm, crtc, size, r, g, b);
-	}
-
-	struct drm_color_lut *gamma = malloc(size * sizeof(struct drm_color_lut));
-	if (gamma == NULL) {
-		wlr_log(WLR_ERROR, "Failed to allocate gamma table");
-		return false;
-	}
-
-	for (size_t i = 0; i < size; i++) {
-		gamma[i].red = r[i];
-		gamma[i].green = g[i];
-		gamma[i].blue = b[i];
-	}
-
-	if (crtc->gamma_lut != 0) {
-		drmModeDestroyPropertyBlob(drm->fd, crtc->gamma_lut);
-	}
-
-	if (drmModeCreatePropertyBlob(drm->fd, gamma,
-			size * sizeof(struct drm_color_lut), &crtc->gamma_lut)) {
-		free(gamma);
-		wlr_log_errno(WLR_ERROR, "Unable to create property blob");
-		return false;
-	}
-	free(gamma);
-
-	struct atomic atom;
-	atomic_begin(crtc, &atom);
-	atomic_add(&atom, crtc->id, crtc->props.gamma_lut, crtc->gamma_lut);
-	return atomic_end(drm->fd, 0, &atom);
-}
-
 static size_t atomic_crtc_get_gamma_size(struct wlr_drm_backend *drm,
 		struct wlr_drm_crtc *crtc) {
 	if (crtc->props.gamma_lut_size == 0) {
@@ -254,6 +269,5 @@ const struct wlr_drm_interface atomic_iface = {
 	.conn_enable = atomic_conn_enable,
 	.crtc_pageflip = atomic_crtc_pageflip,
 	.crtc_set_cursor = atomic_crtc_set_cursor,
-	.crtc_set_gamma = atomic_crtc_set_gamma,
 	.crtc_get_gamma_size = atomic_crtc_get_gamma_size,
 };

backend/drm/backend.c

@@ -93,6 +93,7 @@ static void session_signal(struct wl_listener *listener, void *data) {
 
 		struct wlr_drm_connector *conn;
 		wl_list_for_each(conn, &drm->outputs, link){
+			conn->crtc->pending |= WLR_DRM_CRTC_GAMMA_LUT;
 			if (conn->output.enabled && conn->output.current_mode != NULL) {
 				drm_connector_set_mode(&conn->output,
 						conn->output.current_mode);
@@ -112,16 +113,6 @@ static void session_signal(struct wl_listener *listener, void *data) {
 			}
 
 			drm->iface->crtc_set_cursor(drm, conn->crtc, bo);
-
-			if (conn->crtc->gamma_table != NULL) {
-				size_t size = conn->crtc->gamma_table_size;
-				uint16_t *r = conn->crtc->gamma_table;
-				uint16_t *g = conn->crtc->gamma_table + size;
-				uint16_t *b = conn->crtc->gamma_table + 2 * size;
-				drm->iface->crtc_set_gamma(drm, conn->crtc, size, r, g, b);
-			} else {
-				set_drm_connector_gamma(&conn->output, 0, NULL, NULL, NULL);
-			}
 		}
 	} else {
 		wlr_log(WLR_INFO, "DRM fd paused");

backend/drm/drm.c

@@ -586,7 +586,6 @@ static size_t drm_connector_get_gamma_size(struct wlr_output *output) {
 bool set_drm_connector_gamma(struct wlr_output *output, size_t size,
 		const uint16_t *r, const uint16_t *g, const uint16_t *b) {
 	struct wlr_drm_connector *conn = get_drm_connector_from_output(output);
-	struct wlr_drm_backend *drm = get_drm_backend_from_backend(output->backend);
 
 	if (!conn->crtc) {
 		return false;
@@ -618,17 +617,13 @@ bool set_drm_connector_gamma(struct wlr_output *output, size_t size,
 		memcpy(_b, b, size * sizeof(uint16_t));
 	}
 
-	bool ok = drm->iface->crtc_set_gamma(drm, conn->crtc, size, _r, _g, _b);
+	conn->crtc->pending |= WLR_DRM_CRTC_GAMMA_LUT;
-	if (ok) {
+	free(conn->crtc->gamma_table);
-		wlr_output_update_needs_frame(output);
+	conn->crtc->gamma_table = gamma_table;
+	conn->crtc->gamma_table_size = size;
 
-		free(conn->crtc->gamma_table);
+	wlr_output_update_needs_frame(output);
-		conn->crtc->gamma_table = gamma_table;
+	return true; // will be applied on next page-flip
-		conn->crtc->gamma_table_size = size;
-	} else {
-		free(gamma_table);
-	}
-	return ok;
 }
 
 static bool drm_connector_export_dmabuf(struct wlr_output *output,

backend/drm/legacy.c

@@ -30,6 +30,12 @@ static bool legacy_crtc_pageflip(struct wlr_drm_backend *drm,
 		}
 	}
 
+	if (crtc->pending & WLR_DRM_CRTC_GAMMA_LUT) {
+		if (!drm_legacy_crtc_set_gamma(drm, crtc)) {
+			return false;
+		}
+	}
+
 	if (cursor != NULL && cursor->cursor_enabled && drmModeMoveCursor(drm->fd,
 			crtc->id, conn->cursor_x, conn->cursor_y) != 0) {
 		wlr_log_errno(WLR_ERROR, "%s: failed to move cursor", conn->output.name);
@@ -83,10 +89,22 @@ bool legacy_crtc_set_cursor(struct wlr_drm_backend *drm,
 	return true;
 }
 
-static bool legacy_crtc_set_gamma(struct wlr_drm_backend *drm,
+bool drm_legacy_crtc_set_gamma(struct wlr_drm_backend *drm,
-		struct wlr_drm_crtc *crtc, size_t size,
+		struct wlr_drm_crtc *crtc) {
-		uint16_t *r, uint16_t *g, uint16_t *b) {
+	uint32_t size = crtc->gamma_table_size;
-	return !drmModeCrtcSetGamma(drm->fd, crtc->id, (uint32_t)size, r, g, b);
+	uint16_t *r = NULL, *g = NULL, *b = NULL;
+	if (size > 0) {
+		r = crtc->gamma_table;
+		g = crtc->gamma_table + crtc->gamma_table_size;
+		b = crtc->gamma_table + 2 * crtc->gamma_table_size;
+	}
+
+	if (drmModeCrtcSetGamma(drm->fd, crtc->id, size, r, g, b) != 0) {
+		wlr_log_errno(WLR_ERROR, "Failed to set gamma LUT on CRTC %"PRIu32,
+			crtc->id);
+		return false;
+	}
+	return true;
 }
 
 static size_t legacy_crtc_get_gamma_size(struct wlr_drm_backend *drm,
@@ -98,6 +116,5 @@ const struct wlr_drm_interface legacy_iface = {
 	.conn_enable = legacy_conn_enable,
 	.crtc_pageflip = legacy_crtc_pageflip,
 	.crtc_set_cursor = legacy_crtc_set_cursor,
-	.crtc_set_gamma = legacy_crtc_set_gamma,
 	.crtc_get_gamma_size = legacy_crtc_get_gamma_size,
 };

include/backend/drm/drm.h

@@ -44,6 +44,7 @@ struct wlr_drm_plane {
 
 enum wlr_drm_crtc_field {
 	WLR_DRM_CRTC_MODE = 1 << 0,
+	WLR_DRM_CRTC_GAMMA_LUT = 1 << 1,
 };
 
 struct wlr_drm_crtc {

include/backend/drm/iface.h

@@ -22,10 +22,6 @@ struct wlr_drm_interface {
 	// Enable the cursor buffer on crtc. Set bo to NULL to disable
 	bool (*crtc_set_cursor)(struct wlr_drm_backend *drm,
 		struct wlr_drm_crtc *crtc, struct gbm_bo *bo);
-	// Set the gamma lut on crtc
-	bool (*crtc_set_gamma)(struct wlr_drm_backend *drm,
-		struct wlr_drm_crtc *crtc, size_t size,
-		uint16_t *r, uint16_t *g, uint16_t *b);
 	// Get the gamma lut size of a crtc
 	size_t (*crtc_get_gamma_size)(struct wlr_drm_backend *drm,
 		struct wlr_drm_crtc *crtc);
@@ -34,4 +30,7 @@ struct wlr_drm_interface {
 extern const struct wlr_drm_interface atomic_iface;
 extern const struct wlr_drm_interface legacy_iface;
 
+bool drm_legacy_crtc_set_gamma(struct wlr_drm_backend *drm,
+	struct wlr_drm_crtc *crtc);
+
 #endif