[Intel-gfx] [PATCH] drm/i915: Engine discovery query

[Chris Wilson]

Quoting Tvrtko Ursulin (2018-10-01 17:41:00)
> 
> On 01/10/2018 17:24, Chris Wilson wrote:
> > Quoting Tvrtko Ursulin (2018-10-01 17:15:24)
> >> +       len = sizeof(struct drm_i915_query_engine_info) +
> >> +             I915_NUM_ENGINES * sizeof(struct drm_i915_engine_info);
> > 
> > Since I915_NUM_ENGINES is not ABI, and this will be using a 2-step
> > query (1st to find length, 2nd to grab details), it should work with
> > info->num_rings. If not, we have problems later ;)
> 
> I don't follow, what do you plan to enumerate that would cause a problem?

All I'm suggesting is to avoid any notion that this length is fixed
indefinitely :)
-Chris