/* Control Endpoint Process when underflow condition has occurred.  */
static void udd_ctrl_underflow(void *pointer)
/* Control Endpoint Process when underflow condition has occurred.  */
static void udd_ctrl_underflow(void *pointer)
{
	struct usb_endpoint_callback_parameter *ep_callback_para = (struct usb_endpoint_callback_parameter*)pointer;
	if (UDD_EPCTRL_DATA_OUT == udd_ep_control_state) {
		udd_ctrl_send_zlp_in();
	} else if (UDD_EPCTRL_HANDSHAKE_WAIT_OUT_ZLP == udd_ep_control_state) {
		usb_device_endpoint_set_halt(&usb_device, ep_callback_para->endpoint_address);
	}
}