VCC_BUFF_LEN
(tty_buffer_request_room(tty->port, VCC_BUFF_LEN) < VCC_BUFF_LEN))
tosend = min(VCC_BUFF_LEN, port->chars_in_buffer);
(VCC_BUFF_LEN - port->chars_in_buffer));
num = VCC_BUFF_LEN - port->chars_in_buffer;