static int process_output(unsigned char c, struct tty_struct *tty)
{
	struct n_tty_data *ldata = tty->disc_data;
	int	space, retval;

	mutex_lock(&ldata->output_lock);

	space = tty_write_room(tty);
	retval = do_output_char(c, tty, space);

	mutex_unlock(&ldata->output_lock);
	if (retval < 0)
		return -1;
	else
		return 0;
}
static int process_output(unsigned char c, struct tty_struct *tty)
{
	struct n_tty_data *ldata = tty->disc_data;
	int	space, retval;

	mutex_lock(&ldata->output_lock);

	space = tty_write_room(tty);
	retval = do_output_char(c, tty, space);

	mutex_unlock(&ldata->output_lock);
	if (retval < 0)
		return -1;
	else
		return 0;
}