static int sixpack_ioctl(struct tty_struct *tty, unsigned int cmd,
		unsigned long arg)
{
	struct sixpack *sp = sp_get(tty);
	struct net_device *dev;
	unsigned int tmp, err;

	if (!sp)
		return -ENXIO;
	dev = sp->dev;

	switch(cmd) {
	case SIOCGIFNAME:
		err = copy_to_user((void __user *) arg, dev->name,
		                   strlen(dev->name) + 1) ? -EFAULT : 0;
		break;

	case SIOCGIFENCAP:
		err = put_user(0, (int __user *) arg);
		break;

	case SIOCSIFENCAP:
		if (get_user(tmp, (int __user *) arg)) {
			err = -EFAULT;
			break;
		}

		sp->mode = tmp;
		dev->addr_len        = AX25_ADDR_LEN;
		dev->hard_header_len = AX25_KISS_HEADER_LEN +
		                       AX25_MAX_HEADER_LEN + 3;
		dev->type            = ARPHRD_AX25;

		err = 0;
		break;

	case SIOCSIFHWADDR: {
			char addr[AX25_ADDR_LEN];

			if (copy_from_user(&addr,
					   (void __user *)arg, AX25_ADDR_LEN)) {
				err = -EFAULT;
				break;
			}

			netif_tx_lock_bh(dev);
			__dev_addr_set(dev, &addr, AX25_ADDR_LEN);
			netif_tx_unlock_bh(dev);
			err = 0;
			break;
		}
	default:
		err = tty_mode_ioctl(tty, cmd, arg);
	}

	sp_put(sp);

	return err;
}