KMS enums and bitfields UAPI

[Adam Jackson]

On Fri, 2020-04-03 at 15:24 +0300, Pekka Paalanen wrote:
> On Fri, 03 Apr 2020 10:15:21 +0000 Simon Ser <contact at emersion.fr> wrote:
> 
> > Additionally, I've heard Pekka saying that it would be nice to have constants
> > for property names in the UAPI headers. Indeed, this would prevent
> > hard-to-debug typo issues. I have a very good example of such a typo issue that
> > took literally hours to debug, with X11 atoms which also use free-form strings
> > like KMS properties [3].
> > 
> > If we have constants for property names in UAPI headers, it wouldn't be a big
> > hurdle to also have constants for enum values alongside.
> 
> To clarify, the property names would be of the form
> 
> #define DRM_KMS_PROPERTY_KERBLAH "KerBlah"
> 
> while enum values would be integers, i.e. the raw values.
> 
> Daniel Stone did have a good counter-argument to defining property
> names: userspace would be full of
> 
> #ifndef DRM_KMS_PROPERTY_KERBLAH
> #define DRM_KMS_PROPERTY_KERBLAH "KerBleh"
> #endif
> 
> anyway as long as they cannot rely on the headers to be recent enough.
> (The typo is intentional.)

Why not put this in some external registry and regularly sync it into
drm-next? This seems like an xorgproto kind of problem to me.

- ajax