Add atomic gamma lut size fetching

Legacy gamma lut size now uses the new legacy_crtc member of
wlr_drm_crtc. This was Previously doen using old_crtc in
wlr_drm_connector, but since this refers to the crtc that was connected to
the ouput, this could give the wrong result.

backend/drm/atomic.c

@@ -226,10 +226,24 @@ static bool atomic_crtc_set_gamma(struct wlr_drm_backend *drm,
 	return atomic_end(drm->fd, &atom);
 }
 
+static uint32_t atomic_crtc_get_gamma_size(struct wlr_drm_backend *drm,
+		struct wlr_drm_crtc *crtc) {
+	uint64_t gamma_lut_size;
+
+	if (!wlr_drm_get_prop(drm->fd, crtc->id, crtc->props.gamma_lut_size,
+			   &gamma_lut_size)) {
+		wlr_log(L_ERROR, "Unable to get gamma lut size");
+		return 0;
+	}
+
+	return (uint32_t) gamma_lut_size;
+}
+
 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_move_cursor = atomic_crtc_move_cursor,
 	.crtc_set_gamma = atomic_crtc_set_gamma,
+	.crtc_get_gamma_size = atomic_crtc_get_gamma_size,
 };

backend/drm/drm.c

@@ -140,6 +140,7 @@ bool wlr_drm_resources_init(struct wlr_drm_backend *drm) {
 	for (size_t i = 0; i < drm->num_crtcs; ++i) {
 		struct wlr_drm_crtc *crtc = &drm->crtcs[i];
 		crtc->id = res->crtcs[i];
+		crtc->legacy_crtc = drmModeGetCrtc(drm->fd, crtc->id);
 		wlr_drm_get_crtc_props(drm->fd, crtc->id, &crtc->props);
 	}
 
@@ -166,6 +167,7 @@ void wlr_drm_resources_free(struct wlr_drm_backend *drm) {
 	for (size_t i = 0; i < drm->num_crtcs; ++i) {
 		struct wlr_drm_crtc *crtc = &drm->crtcs[i];
 		drmModeAtomicFree(crtc->atomic);
+		drmModeFreeCrtc(crtc->legacy_crtc);
 		if (crtc->mode_id) {
 			drmModeDestroyPropertyBlob(drm->fd, crtc->mode_id);
 		}
@@ -235,8 +237,8 @@ static void wlr_drm_connector_set_gamma(struct wlr_output *output,
 
 static uint32_t wlr_drm_connector_get_gamma_size(struct wlr_output *output) {
 	struct wlr_drm_connector *conn = (struct wlr_drm_connector *)output;
-	drmModeCrtc *crtc = conn->old_crtc;
+	struct wlr_drm_backend *drm = (struct wlr_drm_backend *)output->backend;
-	return crtc ? crtc->gamma_size : 0;
+	return drm->iface->crtc_get_gamma_size(drm, conn->crtc);
 }
 
 void wlr_drm_connector_start_renderer(struct wlr_drm_connector *conn) {

backend/drm/legacy.c

@@ -65,6 +65,10 @@ bool legacy_crtc_set_gamma(struct wlr_drm_backend *drm,
 	return !drmModeCrtcSetGamma(drm->fd, crtc->id, size, r, g, b);
 }
 
+uint32_t legacy_crtc_get_gamma_size(struct wlr_drm_backend *drm,
+		struct wlr_drm_crtc *crtc) {
+	return crtc->legacy_crtc->gamma_size;
+}
 
 const struct wlr_drm_interface legacy_iface = {
 	.conn_enable = legacy_conn_enable,
@@ -72,4 +76,5 @@ const struct wlr_drm_interface legacy_iface = {
 	.crtc_set_cursor = legacy_crtc_set_cursor,
 	.crtc_move_cursor = legacy_crtc_move_cursor,
 	.crtc_set_gamma = legacy_crtc_set_gamma,
+	.crtc_get_gamma_size = legacy_crtc_get_gamma_size,
 };

backend/drm/properties.c

@@ -29,6 +29,7 @@ static const struct prop_info crtc_info[] = {
 #define INDEX(name) (offsetof(union wlr_drm_crtc_props, name) / sizeof(uint32_t))
 	{ "ACTIVE",         INDEX(active) },
 	{ "GAMMA_LUT",      INDEX(gamma_lut) },
+	{ "GAMMA_LUT_SIZE", INDEX(gamma_lut_size) },
 	{ "MODE_ID",        INDEX(mode_id) },
 	{ "rotation",       INDEX(rotation) },
 	{ "scaling mode",   INDEX(scaling_mode) },

include/backend/drm/drm.h

@@ -45,6 +45,9 @@ struct wlr_drm_crtc {
 	uint32_t gamma_lut;
 	drmModeAtomicReq *atomic;
 
+	// Legacy only
+	drmModeCrtc *legacy_crtc;
+
 	union {
 		struct {
 			struct wlr_drm_plane *overlay;

include/backend/drm/iface.h

@@ -31,6 +31,9 @@ struct wlr_drm_interface {
 	bool (*crtc_set_gamma)(struct wlr_drm_backend *drm,
 			struct wlr_drm_crtc *crtc, uint16_t *r, uint16_t *g, uint16_t *b,
 			uint32_t size);
+	// Get the gamma lut size of a crtc
+	uint32_t (*crtc_get_gamma_size)(struct wlr_drm_backend *drm,
+			struct wlr_drm_crtc *crtc);
 };
 
 extern const struct wlr_drm_interface atomic_iface;

include/backend/drm/properties.h

@@ -33,8 +33,9 @@ union wlr_drm_crtc_props {
 		uint32_t active;
 		uint32_t mode_id;
 		uint32_t gamma_lut;
+		uint32_t gamma_lut_size;
 	};
-	uint32_t props[5];
+	uint32_t props[6];
 };
 
 union wlr_drm_plane_props {