backend-drm: keep track of the reason why promoting view to a plane failed

Add enum try_view_on_plane_failure_reasons to help us to keep track of
the reason why promoting view to a plane failed. We also add a variable
to struct weston_paint_node so that we can update this information in
each output repaint.

This will be used in the next commits, in which we add proper surface
dma-buf feedback support.

Signed-off-by: Leandro Ribeiro <leandro.ribeiro@collabora.com>
Reviewed-by: Daniel Stone <daniels@collabora.com>

libweston/backend-drm/drm-internal.h

@@ -227,6 +227,17 @@ enum wdrm_crtc_property {
 	WDRM_CRTC__COUNT
 };
 
+/**
+ * Reasons why placing a view on a plane failed. Needed by the dma-buf feedback.
+ */
+enum try_view_on_plane_failure_reasons {
+	FAILURE_REASONS_NONE = 0,
+	FAILURE_REASONS_FORCE_RENDERER = (1 << 0),
+	FAILURE_REASONS_FB_FORMAT_INCOMPATIBLE = (1 << 1),
+	FAILURE_REASONS_DMABUF_MODIFIER_INVALID = (1 << 2),
+	FAILURE_REASONS_ADD_FB_FAILED = (1 << 3),
+};
+
 struct drm_backend {
 	struct weston_backend base;
 	struct weston_compositor *compositor;
@@ -694,13 +705,15 @@ drm_output_set_cursor_view(struct drm_output *output, struct weston_view *ev);
 
 #ifdef BUILD_DRM_GBM
 extern struct drm_fb *
-drm_fb_get_from_view(struct drm_output_state *state, struct weston_view *ev);
+drm_fb_get_from_view(struct drm_output_state *state, struct weston_view *ev,
+		     uint32_t *try_view_on_plane_failure_reasons);
 extern bool
 drm_can_scanout_dmabuf(struct weston_compositor *ec,
 		       struct linux_dmabuf_buffer *dmabuf);
 #else
 static inline struct drm_fb *
-drm_fb_get_from_view(struct drm_output_state *state, struct weston_view *ev)
+drm_fb_get_from_view(struct drm_output_state *state, struct weston_view *ev,
+		     uint32_t *try_view_on_plane_failure_reasons)
 {
 	return NULL;
 }

libweston/backend-drm/fb.c

@@ -220,7 +220,8 @@ drm_fb_destroy_dmabuf(struct drm_fb *fb)
 
 static struct drm_fb *
 drm_fb_get_from_dmabuf(struct linux_dmabuf_buffer *dmabuf,
-		       struct drm_backend *backend, bool is_opaque)
+		       struct drm_backend *backend, bool is_opaque,
+		       uint32_t *try_view_on_plane_failure_reasons)
 {
 #ifndef HAVE_GBM_FD_IMPORT
 	/* Importing a buffer to KMS requires explicit modifiers, so
@@ -245,8 +246,12 @@ drm_fb_get_from_dmabuf(struct linux_dmabuf_buffer *dmabuf,
 	 * KMS driver can't know. So giving the buffer to KMS is not safe, as
 	 * not knowing its layout can result in garbage being displayed. In
 	 * short, importing a buffer to KMS requires explicit modifiers. */
-	if (dmabuf->attributes.modifier[0] == DRM_FORMAT_MOD_INVALID)
+	if (dmabuf->attributes.modifier[0] == DRM_FORMAT_MOD_INVALID) {
+		if (try_view_on_plane_failure_reasons)
+			*try_view_on_plane_failure_reasons |=
+				FAILURE_REASONS_DMABUF_MODIFIER_INVALID;
 		return NULL;
+	}
 
 	/* XXX: TODO:
 	 *
@@ -313,8 +318,12 @@ drm_fb_get_from_dmabuf(struct linux_dmabuf_buffer *dmabuf,
 		fb->handles[i] = handle.u32;
 	}
 
-	if (drm_fb_addfb(backend, fb) != 0)
+	if (drm_fb_addfb(backend, fb) != 0) {
+		if (try_view_on_plane_failure_reasons)
+			*try_view_on_plane_failure_reasons |=
+				FAILURE_REASONS_ADD_FB_FAILED;
 		goto err_free;
+	}
 
 	return fb;
 
@@ -455,7 +464,7 @@ drm_can_scanout_dmabuf(struct weston_compositor *ec,
 	struct drm_backend *b = to_drm_backend(ec);
 	bool ret = false;
 
-	fb = drm_fb_get_from_dmabuf(dmabuf, b, true);
+	fb = drm_fb_get_from_dmabuf(dmabuf, b, true, NULL);
 	if (fb)
 		ret = true;
 
@@ -466,7 +475,8 @@ drm_can_scanout_dmabuf(struct weston_compositor *ec,
 }
 
 struct drm_fb *
-drm_fb_get_from_view(struct drm_output_state *state, struct weston_view *ev)
+drm_fb_get_from_view(struct drm_output_state *state, struct weston_view *ev,
+		     uint32_t *try_view_on_plane_failure_reasons)
 {
 	struct drm_output *output = state->output;
 	struct drm_backend *b = to_drm_backend(output->base.compositor);
@@ -497,7 +507,8 @@ drm_fb_get_from_view(struct drm_output_state *state, struct weston_view *ev)
 
 	dmabuf = linux_dmabuf_buffer_get(buffer->resource);
 	if (dmabuf) {
-		fb = drm_fb_get_from_dmabuf(dmabuf, b, is_opaque);
+		fb = drm_fb_get_from_dmabuf(dmabuf, b, is_opaque,
+					    try_view_on_plane_failure_reasons);
 		if (!fb)
 			return NULL;
 	} else {

libweston/backend-drm/state-propose.c

@@ -654,7 +654,8 @@ drm_output_prepare_plane_view(struct drm_output_state *state,
 			      struct weston_view *ev,
 			      enum drm_output_propose_state_mode mode,
 			      struct drm_plane_state *scanout_state,
-			      uint64_t current_lowest_zpos)
+			      uint64_t current_lowest_zpos,
+			      uint32_t *try_view_on_plane_failure_reasons)
 {
 	struct drm_output *output = state->output;
 	struct drm_backend *b = to_drm_backend(output->base.compositor);
@@ -676,7 +677,7 @@ drm_output_prepare_plane_view(struct drm_output_state *state,
 
 	buffer = ev->surface->buffer_ref.buffer;
 	shmbuf = wl_shm_buffer_get(buffer->resource);
-	fb = drm_fb_get_from_view(state, ev);
+	fb = drm_fb_get_from_view(state, ev, try_view_on_plane_failure_reasons);
 
 	/* assemble a list with possible candidates */
 	wl_list_for_each(plane, &b->plane_list, link) {
@@ -730,6 +731,8 @@ drm_output_prepare_plane_view(struct drm_output_state *state,
 		}
 
 		if (!drm_output_plane_view_has_valid_format(plane, state, ev, fb)) {
+			*try_view_on_plane_failure_reasons |=
+				FAILURE_REASONS_FB_FORMAT_INCOMPATIBLE;
 			drm_debug(b, "\t\t\t\t[plane] not adding plane %d to "
 				     "candidate list: invalid pixel format\n",
 				     plane->plane_id);
@@ -960,7 +963,18 @@ drm_output_propose_state(struct weston_output *output_base,
 				      current_lowest_zpos);
 			ps = drm_output_prepare_plane_view(state, ev, mode,
 							   scanout_state,
-							   current_lowest_zpos);
+							   current_lowest_zpos,
+							   &pnode->try_view_on_plane_failure_reasons);
+			/* If we were able to place the view in a plane, set
+			 * failure reasons to none. */
+			if (ps)
+				pnode->try_view_on_plane_failure_reasons =
+					FAILURE_REASONS_NONE;
+		} else {
+			/* We are forced to place the view in the renderer, set
+			 * the failure reason accordingly. */
+			pnode->try_view_on_plane_failure_reasons =
+				FAILURE_REASONS_FORCE_RENDERER;
 		}
 
 		if (ps) {

libweston/libweston-internal.h

@@ -416,6 +416,8 @@ struct weston_paint_node {
 
 	struct weston_surface_color_transform surf_xform;
 	bool surf_xform_valid;
+
+	uint32_t try_view_on_plane_failure_reasons;
 };
 
 struct weston_paint_node *