[PATCH] drm: Return -ENOTSUPP in drm_setclientcap() when driver do not support KMS

[Chris Wilson]

Quoting Souza, Jose (2018-09-14 17:30:59)
> On Fri, 2018-09-14 at 09:15 +0100, Chris Wilson wrote:
> > Quoting José Roberto de Souza (2018-09-13 23:13:41)
> > > @@ -306,6 +306,9 @@ drm_setclientcap(struct drm_device *dev, void
> > > *data, struct drm_file *file_priv)
> > >  {
> > >         struct drm_set_client_cap *req = data;
> > >  
> > > +       if (!drm_core_check_feature(dev, DRIVER_MODESET))
> > > +               return -ENOTSUPP;
> > 
> > The wider question though is client cap restricted to modesetting
> > capabilities? Or should each case include a check like
> > DRM_CLIENT_CAP_ATOMIC.
> 
> Well all of those:
> 
> DRM_CLIENT_CAP_STEREO_3D
> DRM_CLIENT_CAP_UNIVERSAL_PLANES
> DRM_CLIENT_CAP_ATOMIC
> DRM_CLIENT_CAP_ASPECT_RATIO
> DRM_CLIENT_CAP_WRITEBACK_CONNECTORS
> 
> are just usefull with KMS.

It more about the semantics. If it's the first guard in the function, it
gives the impression that the setclientcap ioctl is KMS only. If they
are repeated for each case, then it's clear that the ioctl is more
general and it just those caps that are KMS only.

Imo, the drm_client is wider than the kms interface, but I may be wrong.
-Chris