How to set errno in Linux device driver?

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I am designing a Linux character device driver. I want to set errno when error occurs in ioctl() system call.

long my_own_ioctl(struct file *file, unsigned int req, unsigned long arg)
{
    long ret = 0;
    BOOL isErr = FALSE;

    // some operation
    // ...

    if (isErr)
    {
        // set errno
        // ...                 <--- What should I do?
        ret = -1;
    }

    return ret;
}

What should I do to achieve that? Thank you at advance!

asked 1 min ago

Andrew Chang

327