backend-drm: Add dmabuf scan-out check for DRM-backend

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

libweston/backend-drm/drm-internal.h

@@ -682,12 +682,21 @@ drm_fb_get_from_bo(struct gbm_bo *bo, struct drm_backend *backend,
 #ifdef BUILD_DRM_GBM
 extern struct drm_fb *
 drm_fb_get_from_view(struct drm_output_state *state, struct weston_view *ev);
+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)
 {
 	return NULL;
 }
+static inline bool
+drm_can_scanout_dmabuf(struct weston_compositor *ec,
+		       struct linux_dmabuf_buffer *dmabuf)
+{
+	return false;
+}
 #endif
 
 struct drm_pending_state *

libweston/backend-drm/drm.c

@@ -2893,6 +2893,7 @@ drm_backend_create(struct weston_compositor *compositor,
 	b->base.repaint_cancel = drm_repaint_cancel;
 	b->base.create_output = drm_output_create;
 	b->base.device_changed = drm_device_changed;
+	b->base.can_scanout_dmabuf = drm_can_scanout_dmabuf;
 
 	weston_setup_vt_switch_bindings(compositor);
 

libweston/backend-drm/fb.c

@@ -509,6 +509,24 @@ drm_fb_unref(struct drm_fb *fb)
 }
 
 #ifdef BUILD_DRM_GBM
+bool
+drm_can_scanout_dmabuf(struct weston_compositor *ec,
+		       struct linux_dmabuf_buffer *dmabuf)
+{
+	struct drm_fb *fb;
+	struct drm_backend *b = to_drm_backend(ec);
+	bool ret = false;
+
+	fb = drm_fb_get_from_dmabuf(dmabuf, b, true);
+	if (fb)
+		ret = true;
+
+	drm_fb_unref(fb);
+	drm_debug(b, "[dmabuf] dmabuf %p, import test %s\n", dmabuf,
+		      ret ? "succeeded" : "failed");
+	return ret;
+}
+
 struct drm_fb *
 drm_fb_get_from_view(struct drm_output_state *state, struct weston_view *ev)
 {