when to return -EOPNOTSUPP in _ioctl in a driver

[Luis R. Rodriguez]

On Tue, Oct 2, 2012 at 8:26 AM, devendra.aaru <devendra.aaru at gmail.com> wrote:
> Hi all,
>
> While going through some code, i have found a place in which we do return,
> -EOPNOTSUPP in an ioctl and the code of ioctl does just this one.
>
>
> static int drv_ioctl(.. *fops, ...)
> {
>           return -EOPNOTSUPP;
> }
>
>
> do we actually need to specify a pointer to the ioctl callback, if the
> driver doesn't support ioctl?

What type of driver? For networking if you do not have
ops->ndo_do_ioctl then -EOPNOTSUPP is returned. See dev_ifsioc() and
prior to that dev_ioctl() on net/core/dev.c.

  Luis