/* Return the number of bytes of data available in the circular buffer.  */
static int serial_buf_data_avail(struct circ_buf *cb)
/* Return the number of bytes of data available in the circular buffer.  */
static int serial_buf_data_avail(struct circ_buf *cb)
{
	return CIRC_CNT(cb->head, cb->tail, AIRCABLE_BUF_SIZE);
}