backend-drm: Add zpos DRM-property

Functional no change, as nobody makes use of it. Only apply the zpos
value if the zpos property is mutable (that is, zpos_max and zpos_min
are not the same).

Signed-off-by: Marius Vlad <marius.vlad@collabora.com>

libweston/backend-drm/drm-internal.h

@@ -72,6 +72,10 @@
 #define GBM_BO_USE_LINEAR (1 << 4)
 #endif
 
+#ifndef DRM_PLANE_ZPOS_INVALID_PLANE
+#define DRM_PLANE_ZPOS_INVALID_PLANE	0xffffffffffffffffULL
+#endif
+
 /**
  * A small wrapper to print information into the 'drm-backend' debug scope.
  *
@@ -169,6 +173,7 @@ enum wdrm_plane_property {
 	WDRM_PLANE_IN_FORMATS,
 	WDRM_PLANE_IN_FENCE_FD,
 	WDRM_PLANE_FB_DAMAGE_CLIPS,
+	WDRM_PLANE_ZPOS,
 	WDRM_PLANE__COUNT
 };
 
@@ -385,6 +390,8 @@ struct drm_plane_state {
 	int32_t dest_x, dest_y;
 	uint32_t dest_w, dest_h;
 
+	uint64_t zpos;
+
 	bool complete;
 
 	/* We don't own the fd, so we shouldn't close it */
@@ -426,6 +433,9 @@ struct drm_plane {
 	/* The last state submitted to the kernel for this plane. */
 	struct drm_plane_state *state_cur;
 
+	uint64_t zpos_min;
+	uint64_t zpos_max;
+
 	struct wl_list link;
 
 	struct {

libweston/backend-drm/drm.c

@@ -680,6 +680,7 @@ drm_plane_create(struct drm_backend *b, const drmModePlane *kplane,
 {
 	struct drm_plane *plane;
 	drmModeObjectProperties *props;
+	uint64_t *zpos_range_values;
 	uint32_t num_formats = (kplane) ? kplane->count_formats : 1;
 
 	plane = zalloc(sizeof(*plane) +
@@ -711,6 +712,18 @@ drm_plane_create(struct drm_backend *b, const drmModePlane *kplane,
 					       props,
 					       WDRM_PLANE_TYPE__COUNT);
 
+		zpos_range_values =
+			drm_property_get_range_values(&plane->props[WDRM_PLANE_ZPOS], 
+						      props);
+
+		if (zpos_range_values) {
+			plane->zpos_min = zpos_range_values[0];
+			plane->zpos_max = zpos_range_values[1];
+		} else {
+			plane->zpos_min = DRM_PLANE_ZPOS_INVALID_PLANE;
+			plane->zpos_max = DRM_PLANE_ZPOS_INVALID_PLANE;
+		}
+
 		if (drm_plane_populate_formats(plane, kplane, props) < 0) {
 			drmModeFreeObjectProperties(props);
 			goto err;
@@ -724,6 +737,8 @@ drm_plane_create(struct drm_backend *b, const drmModePlane *kplane,
 		plane->count_formats = 1;
 		plane->formats[0].format = format;
 		plane->type = type;
+		plane->zpos_max = DRM_PLANE_ZPOS_INVALID_PLANE;
+		plane->zpos_min = DRM_PLANE_ZPOS_INVALID_PLANE;
 	}
 
 	if (plane->type == WDRM_PLANE_TYPE__COUNT)

libweston/backend-drm/kms.c

@@ -77,6 +77,7 @@ const struct drm_property_info plane_props[] = {
 	[WDRM_PLANE_IN_FORMATS] = { .name = "IN_FORMATS" },
 	[WDRM_PLANE_IN_FENCE_FD] = { .name = "IN_FENCE_FD" },
 	[WDRM_PLANE_FB_DAMAGE_CLIPS] = { .name = "FB_DAMAGE_CLIPS" },
+	[WDRM_PLANE_ZPOS] = { .name = "zpos" },
 };
 
 struct drm_property_enum_info dpms_state_enums[] = {
@@ -1050,6 +1051,13 @@ drm_output_apply_state_atomic(struct drm_output_state *state,
 					      plane_state->in_fence_fd);
 		}
 
+		/* do note, that 'invented' zpos values are set as immutable */
+		if (plane_state->zpos != DRM_PLANE_ZPOS_INVALID_PLANE &&
+		    plane_state->plane->zpos_min != plane_state->plane->zpos_max)
+			ret |= plane_add_prop(req, plane,
+					      WDRM_PLANE_ZPOS,
+					      plane_state->zpos);
+
 		if (ret != 0) {
 			weston_log("couldn't set plane state\n");
 			return ret;

libweston/backend-drm/state-helpers.c

@@ -48,6 +48,7 @@ drm_plane_state_alloc(struct drm_output_state *state_output,
 	state->output_state = state_output;
 	state->plane = plane;
 	state->in_fence_fd = -1;
+	state->zpos = DRM_PLANE_ZPOS_INVALID_PLANE;
 	pixman_region32_init(&state->damage);
 
 	/* Here we only add the plane state to the desired link, and not
@@ -80,6 +81,7 @@ drm_plane_state_free(struct drm_plane_state *state, bool force)
 	wl_list_init(&state->link);
 	state->output_state = NULL;
 	state->in_fence_fd = -1;
+	state->zpos = DRM_PLANE_ZPOS_INVALID_PLANE;
 	pixman_region32_fini(&state->damage);
 
 	if (force || state != state->plane->state_cur) {