On Thu, May 18, 2017 at 01:55:59PM +0300, Joonas Lahtinen wrote: > On ke, 2017-05-17 at 16:40 +0100, Tvrtko Ursulin wrote: >> From: Tvrtko Ursulin <tvrtko.ursulin(a)intel.com&gt; >> >> 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. Note this text doesn't describe the interface in v3. > Would it make sense to use bitmask for future proofing? Then we could > allow passing multiple options in the future. No. The first use case has to be explicit control of engine. That's orthogonal to asking to select any of a particular class.