render/drm_syncobj: add wlr_drm_syncobj_timeline_export()

include/wlr/render/drm_syncobj.h

@@ -62,6 +62,10 @@ struct wlr_drm_syncobj_timeline *wlr_drm_syncobj_timeline_ref(struct wlr_drm_syn
  * Unreference a synchronization timeline.
  */
 void wlr_drm_syncobj_timeline_unref(struct wlr_drm_syncobj_timeline *timeline);
+/**
+ * Export a drm_syncobj FD from a timeline.
+ */
+int wlr_drm_syncobj_timeline_export(struct wlr_drm_syncobj_timeline *timeline);
 /**
  * Transfer a point from a timeline to another.
  *

render/drm_syncobj.c

@@ -67,6 +67,15 @@ void wlr_drm_syncobj_timeline_unref(struct wlr_drm_syncobj_timeline *timeline) {
 	free(timeline);
 }
 
+int wlr_drm_syncobj_timeline_export(struct wlr_drm_syncobj_timeline *timeline) {
+	int drm_syncobj_fd = -1;
+	if (drmSyncobjHandleToFD(timeline->drm_fd, timeline->handle, &drm_syncobj_fd) != 0) {
+		wlr_log_errno(WLR_ERROR, "drmSyncobjHandleToFD failed");
+		return -1;
+	}
+	return drm_syncobj_fd;
+}
+
 bool wlr_drm_syncobj_timeline_transfer(struct wlr_drm_syncobj_timeline *dst,
 		uint64_t dst_point, struct wlr_drm_syncobj_timeline *src, uint64_t src_point) {
 	assert(dst->drm_fd == src->drm_fd);