If a driver sets driver_data but not driver_free_cb, driver_data will get freed along with the command. If a driver sets driver_free_cb, driver_data will not get automatically freed but the callback will get called before the rest of the data structure is freed. Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com> Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/15329>