[PATCH v3] drm: Differentiate the lack of an interface from invalid parameter

[Chris Wilson]

Quoting Chris Wilson (2018-09-13 20:20:50)
> If the ioctl is not supported on a particular piece of HW/driver
> combination, report ENOTSUP (aka EOPNOTSUPP) so that it can be easily
> distinguished from both the lack of the ioctl and from a regular invalid
> parameter.
> 
> v2: Across all the kms ioctls we had a mixture of reporting EINVAL,
> ENODEV and a few ENOTSUPP (most where EINVAL) for a failed
> drm_core_check_feature(). Update everybody to report ENOTSUPP.
> 
> v3: ENOTSUPP is an internal errno! It's value (524) does not correspond
> to a POSIX errno, the one we want is ENOTSUP. However,
> uapi/asm-generic/errno.h doesn't include ENOTSUP but man errno says
> 
>         "ENOTSUP and EOPNOTSUPP have the same value on Linux,
>         but according to POSIX.1 these error values should be
>         distinct."
> 
> so use EOPNOTSUPP as its equivalent.
> 
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Daniel Vetter <daniel at ffwll.ch>
> Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
> Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch> #v2

And pushed to drm-misc-next, so hopefully the ENOTSUP/EOPNOTSUPP is all
fine. Thanks for the review,
-Chris