render/drm_syncobj: add wlr_drm_syncobj_timeline_import()

include/wlr/render/drm_syncobj.h

@@ -37,6 +37,11 @@ struct wlr_drm_syncobj_timeline {
  * Create a new synchronization timeline.
  */
 struct wlr_drm_syncobj_timeline *wlr_drm_syncobj_timeline_create(int drm_fd);
+/**
+ * Import a timeline from a drm_syncobj FD.
+ */
+struct wlr_drm_syncobj_timeline *wlr_drm_syncobj_timeline_import(int drm_fd,
+	int drm_syncobj_fd);
 /**
  * Reference a synchronization timeline.
  */

render/drm_syncobj.c

@@ -21,6 +21,24 @@ struct wlr_drm_syncobj_timeline *wlr_drm_syncobj_timeline_create(int drm_fd) {
 	return timeline;
 }
 
+struct wlr_drm_syncobj_timeline *wlr_drm_syncobj_timeline_import(int drm_fd,
+		int drm_syncobj_fd) {
+	struct wlr_drm_syncobj_timeline *timeline = calloc(1, sizeof(*timeline));
+	if (timeline == NULL) {
+		return NULL;
+	}
+	timeline->drm_fd = drm_fd;
+	timeline->n_refs = 1;
+
+	if (drmSyncobjFDToHandle(drm_fd, drm_syncobj_fd, &timeline->handle) != 0) {
+		wlr_log_errno(WLR_ERROR, "drmSyncobjFDToHandle failed");
+		free(timeline);
+		return NULL;
+	}
+
+	return timeline;
+}
+
 struct wlr_drm_syncobj_timeline *wlr_drm_syncobj_timeline_ref(struct wlr_drm_syncobj_timeline *timeline) {
 	timeline->n_refs++;
 	return timeline;