/* Request the Tx or Rx buffers on the USB side be flushed. 
Tx flush: When all the currently buffered data has been sent, send an escape sequence back up the data stream to us Rx flush: add a flag in the data stream now so we know when it's made it's way up to us.  */
static int qt2_box_flush(struct usb_serial *serial, unsigned char uart_number, unsigned short rcv_or_xmit)
/* Request the Tx or Rx buffers on the USB side be flushed. 
Tx flush: When all the currently buffered data has been sent, send an escape sequence back up the data stream to us Rx flush: add a flag in the data stream now so we know when it's made it's way up to us.  */
static int qt2_box_flush(struct usb_serial *serial, unsigned char uart_number, unsigned short rcv_or_xmit)
{
	int result;
	result = usb_control_msg(serial->dev, usb_rcvctrlpipe(serial->dev, 0),
		QT2_FLUSH_DEVICE, 0x40, rcv_or_xmit, uart_number, NULL, 0,
		300);
	return result;
}