int ret = 0;
    int remains;
    struct uart16550_line_info *data = NULL;

    switch (cmd) {
    case UART16550_IOCTL_SET_LINE:
        remains = copy_from_user(data, (struct uart16550_line_info __user *)arg,
                sizeof(struct uart16550_line_info *));
        if (remains) {
            ret = -EFAULT;
        }
        break;
    default:
        ret = -EINVAL;
    }
    return ret;