backend-drm: Drop support to non universal plane drivers

Remove all the backend code to support drivers without universal planes.

From[1]:

"The code needed to support kernels where DRM does not support uiniversal
planes makes the DRM-backend a little more complicated, because it needs
to create fake planes for primary and cursor. The lifetimes of the fake
planes does not match the lifetime of "proper" planes, which is surprising."

And since the universal planes left the experimetal flag in 2014[2] it is
safe to remove the support now.

[1] https://gitlab.freedesktop.org/wayland/weston/-/issues/427
[2] https://cgit.freedesktop.org/drm/drm-tip/commit/?id=c7dbc6c9ae5c3baa3be755a228a349374d043b5b

Signed-off-by: Igor Matheus Andrade Torrente <igormtorrente@gmail.com>

libweston/backend-drm/drm-internal.h

@@ -269,7 +269,6 @@ struct drm_backend {
 	bool sprites_are_broken;
 	bool cursors_are_broken;
 
-	bool universal_planes;
 	bool atomic_modeset;
 
 	bool use_pixman;

libweston/backend-drm/drm.c

@@ -736,10 +736,6 @@ init_pixman(struct drm_backend *b)
  * Creates one drm_plane structure for a hardware plane, and initialises its
  * properties and formats.
  *
- * In the absence of universal plane support, where KMS does not explicitly
- * expose the primary and cursor planes to userspace, this may also create
- * an 'internal' plane for internal management.
- *
  * This function does not add the plane to the list of usable planes in Weston
  * itself; the caller is responsible for this.
  *
@@ -747,20 +743,14 @@ init_pixman(struct drm_backend *b)
  *
  * @sa drm_output_find_special_plane
  * @param b DRM compositor backend
- * @param kplane DRM plane to create, or NULL if creating internal plane
+ * @param kplane DRM plane to create
- * @param output Output to create internal plane for, or NULL
- * @param type Type to use when creating internal plane, or invalid
- * @param format Format to use for internal planes, or 0
  */
 static struct drm_plane *
-drm_plane_create(struct drm_backend *b, const drmModePlane *kplane,
+drm_plane_create(struct drm_backend *b, const drmModePlane *kplane)
-		 struct drm_output *output, enum wdrm_plane_type type,
-		 uint32_t format)
 {
 	struct drm_plane *plane;
 	drmModeObjectProperties *props;
 	uint64_t *zpos_range_values;
-	struct weston_drm_format *fmt;
 
 	plane = zalloc(sizeof(*plane));
 	if (!plane) {
@@ -771,19 +761,18 @@ drm_plane_create(struct drm_backend *b, const drmModePlane *kplane,
 	plane->backend = b;
 	plane->state_cur = drm_plane_state_alloc(NULL, plane);
 	plane->state_cur->complete = true;
-
-	weston_drm_format_array_init(&plane->formats);
-
-	if (kplane) {
 	plane->possible_crtcs = kplane->possible_crtcs;
 	plane->plane_id = kplane->plane_id;
 
+	weston_drm_format_array_init(&plane->formats);
+
 	props = drmModeObjectGetProperties(b->drm.fd, kplane->plane_id,
 					   DRM_MODE_OBJECT_PLANE);
 	if (!props) {
 		weston_log("couldn't get plane properties\n");
 		goto err;
 	}
+
 	drm_property_info_populate(b, plane_props, plane->props,
 				   WDRM_PLANE__COUNT, props);
 	plane->type =
@@ -810,40 +799,10 @@ drm_plane_create(struct drm_backend *b, const drmModePlane *kplane,
 	}
 
 	drmModeFreeObjectProperties(props);
-	}
-	else {
-		plane->possible_crtcs = (1 << output->crtc->pipe);
-		plane->plane_id = 0;
-		plane->type = type;
-		plane->zpos_max = DRM_PLANE_ZPOS_INVALID_PLANE;
-		plane->zpos_min = DRM_PLANE_ZPOS_INVALID_PLANE;
-
-		/* Without universal planes support we can't tell the formats
-		 * and modifiers that the plane support, as we don't know
-		 * anything about the planes. So modifiers are not supported. */
-		fmt = weston_drm_format_array_add_format(&plane->formats, format);
-		if (!fmt)
-			goto err;
-		if (!weston_drm_format_add_modifier(fmt, DRM_FORMAT_MOD_INVALID))
-			goto err;
-	}
 
 	if (plane->type == WDRM_PLANE_TYPE__COUNT)
 		goto err_props;
 
-	/* With universal planes, everything is a DRM plane; without
-	 * universal planes, the only DRM planes are overlay planes.
-	 * Everything else is a fake plane. */
-	if (b->universal_planes) {
-		assert(kplane);
-	} else {
-		if (kplane)
-			assert(plane->type == WDRM_PLANE_TYPE_OVERLAY);
-		else
-			assert(plane->type != WDRM_PLANE_TYPE_OVERLAY &&
-			       output);
-	}
-
 	weston_plane_init(&plane->base, b->compositor, 0, 0);
 	wl_list_insert(&b->plane_list, &plane->link);
 
@@ -861,20 +820,6 @@ err:
 /**
  * Find, or create, a special-purpose plane
  *
- * Primary and cursor planes are a special case, in that before universal
- * planes, they are driven by non-plane API calls. Without universal plane
- * support, the only way to configure a primary plane is via drmModeSetCrtc,
- * and the only way to configure a cursor plane is drmModeSetCursor2.
- *
- * Although they may actually be regular planes in the hardware, without
- * universal plane support, these planes are not actually exposed to
- * userspace in the regular plane list.
- *
- * However, for ease of internal tracking, we want to manage all planes
- * through the same drm_plane structures. Therefore, when we are running
- * without universal plane support, we create fake drm_plane structures
- * to track these planes.
- *
  * @param b DRM backend
  * @param output Output to use for plane
  * @param type Type of plane
@@ -885,27 +830,6 @@ drm_output_find_special_plane(struct drm_backend *b, struct drm_output *output,
 {
 	struct drm_plane *plane;
 
-	if (!b->universal_planes) {
-		uint32_t format;
-
-		switch (type) {
-		case WDRM_PLANE_TYPE_CURSOR:
-			format = DRM_FORMAT_ARGB8888;
-			break;
-		case WDRM_PLANE_TYPE_PRIMARY:
-			/* We don't know what formats the primary plane supports
-			 * before universal planes, so we just assume that the
-			 * GBM format works. */
-			format = output->gbm_format;
-			break;
-		default:
-			assert(!"invalid type in drm_output_find_special_plane");
-			break;
-		}
-
-		return drm_plane_create(b, NULL, output, type, format);
-	}
-
 	wl_list_for_each(plane, &b->plane_list, link) {
 		struct drm_output *tmp;
 		bool found_elsewhere = false;
@@ -986,8 +910,7 @@ create_sprites(struct drm_backend *b)
 		if (!kplane)
 			continue;
 
-		drm_plane = drm_plane_create(b, kplane, NULL,
+		drm_plane = drm_plane_create(b, kplane);
-		                             WDRM_PLANE_TYPE__COUNT, 0);
 		drmModeFreePlane(kplane);
 		if (!drm_plane)
 			continue;
@@ -1706,9 +1629,7 @@ drm_output_init_planes(struct drm_output *output)
 }
 
 /** The opposite of drm_output_init_planes(). First of all it removes the planes
- * from the plane stacking list. Then, in case we don't have support for
+ * from the plane stacking list. After all it sets the planes of the output as NULL.
- * universal planes it destroys the planes. After all it sets the planes of the
- * output as NULL.
  */
 static void
 drm_output_deinit_planes(struct drm_output *output)
@@ -1728,27 +1649,16 @@ drm_output_deinit_planes(struct drm_output *output)
 			drmModeSetCursor(b->drm.fd, output->crtc->crtc_id, 0, 0, 0);
 		}
 
-		if (!b->universal_planes) {
+		/* With universal planes, the planes are allocated at startup,
-			/* Without universal planes, our special planes are
+		 * freed at shutdown, and live on the plane list in between.
-			 * pseudo-planes allocated at output creation, freed at
+		 * We want the planes to  continue to exist and be freed up
-			 * output destruction, and not usable by other outputs.
+		 * for other outputs.
-			 */
-			if (output->cursor_plane)
-				drm_plane_destroy(output->cursor_plane);
-			if (output->scanout_plane)
-				drm_plane_destroy(output->scanout_plane);
-		} else {
-			/* With universal planes, the 'special' planes are
-			 * allocated at startup, freed at shutdown, and live on
-			 * the plane list in between. We want the planes to
-			 * continue to exist and be freed up for other outputs.
 		 */
 		if (output->cursor_plane)
 			drm_plane_reset_state(output->cursor_plane);
 		if (output->scanout_plane)
 			drm_plane_reset_state(output->scanout_plane);
 	}
-	}
 
 	output->cursor_plane = NULL;
 	output->scanout_plane = NULL;

libweston/backend-drm/kms.c

@@ -1447,12 +1447,13 @@ init_kms_caps(struct drm_backend *b)
 	else
 		b->cursor_height = 64;
 
-	if (!getenv("WESTON_DISABLE_UNIVERSAL_PLANES")) {
 	ret = drmSetClientCap(b->drm.fd, DRM_CLIENT_CAP_UNIVERSAL_PLANES, 1);
-		b->universal_planes = (ret == 0);
+	if (ret) {
+		weston_log("Error: drm card doesn't support universal planes!\n");
+		return -1;
 	}
 
-	if (b->universal_planes && !getenv("WESTON_DISABLE_ATOMIC")) {
+	if (!getenv("WESTON_DISABLE_ATOMIC")) {
 		ret = drmGetCap(b->drm.fd, DRM_CAP_CRTC_IN_VBLANK_EVENT, &cap);
 		if (ret != 0)
 			cap = 0;