The MediaDevice::driver(), deviceNode() and model() functions return a const std::string, copying the string stored internally in the class. Return references instead to avoid copies. Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com> Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>