/* This routine returns the numbers of characteres the tty driver will accept for queuing to be written. o return MTU  */
static int cpc_tty_write_room(struct tty_struct *tty)
/* This routine returns the numbers of characteres the tty driver will accept for queuing to be written. o return MTU  */
static int cpc_tty_write_room(struct tty_struct *tty)
{
	st_cpc_tty_area    *cpc_tty; 
	if (!tty || !tty->driver_data ) { 
		CPC_TTY_DBG("hdlcX-tty: no TTY to write room\n");
		return -ENODEV;
	}
	cpc_tty = (st_cpc_tty_area *) tty->driver_data; 
	if ((cpc_tty->tty != tty) ||  (cpc_tty->state != CPC_TTY_ST_OPEN)) { 
		CPC_TTY_DBG("%s: TTY is not opened\n",cpc_tty->name);
		return -ENODEV; 
	}
   	CPC_TTY_DBG("%s: write room\n",cpc_tty->name);
	return CPC_TTY_MAX_MTU;
}