[Intel-gfx] [PATCH v5 2/9] drm/i915: Define an engine class enum for the uABI

[Chris Wilson]

Quoting Tvrtko Ursulin (2017-11-09 10:04:17)
> 
> On 09/11/2017 09:37, Chris Wilson wrote:
> > Quoting Tvrtko Ursulin (2017-11-09 09:27:33)
> >>
> >> On 09/11/2017 09:13, Lionel Landwerlin wrote:
> >>> On 08/11/17 19:14, Chris Wilson wrote:
> >>>> +/*
> >>>> + * Different engines serve different roles, and there may be more
> >>>> than one
> >>>> + * engine serving each role. enum drm_i915_gem_engine_class provides a
> >>>> + * classification of the role of the engine, which may be used when
> >>>> requesting
> >>>> + * operations to be performed on a certain subset of engines, or for
> >>>> providing
> >>>> + * information about that group.
> >>>> + */
> >>>> +enum drm_i915_gem_engine_class {
> >>>> +    I915_ENGINE_CLASS_OTHER = 0,
> >>>> +    I915_ENGINE_CLASS_RENDER = 1,
> >>>> +    I915_ENGINE_CLASS_COPY = 2,
> >>>> +    I915_ENGINE_CLASS_VIDEO = 3,
> >>>> +    I915_ENGINE_CLASS_VIDEO_ENHANCE = 4,
> >>>> +};
> >>>> +
> >>> I've tried to build a bit UI in GPUTop to show this.
> >>> I'm a bit skeptical about the OTHER type because if this enum is meant
> >>> to be extended, then why do we need an OTHER class? We should create new
> >>> classes instead.
> >>
> >> Good point, I agree that I cannot find a reason why we would have it in
> >> the uAPI. I suspect I was just doing a copy-paste-transform of the
> >> hardware definitions from i915_reg.h.
> > 
> > Do we want to keep 0 as undefined? It can be both a nuisance and a
> > blessing...
> 
> What can you imagine it would be useful for?

I915_EXEC_DEFAULT is of I915_ENGINE_CLASS_OTHER.
-Chris