[Intel-gfx] [RFC v3] drm/i915: Select engines via class and instance in execbuffer2

[Joonas Lahtinen]

On ke, 2017-05-17 at 16:40 +0100, Tvrtko Ursulin wrote:
> From: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> 
> Building on top of the previous patch which exported the concept
> of engine classes and instances, we can also use this instead of
> the current awkward engine selection uAPI.
> 
> This is primarily interesting for the VCS engine selection which
> is a) currently done via disjoint set of flags, and b) the
> current I915_EXEC_BSD flags has different semantics depending on
> the underlying hardware which is bad.
> 
> Proposed idea here is to reserve 16-bits of flags, to pass in
> the engine class and instance (8 bits each), and a new flag
> named I915_EXEC_CLASS_INSTACE to tell the kernel this new engine
> selection API is in use.

Would it make sense to use bitmask for future proofing? Then we could
allow passing multiple options in the future.

Other than that, looks good. Chris already commented some on the code
itself.

Regards, Joonas
-- 
Joonas Lahtinen
Open Source Technology Center
Intel Corporation