user_engines
e = user_engines(ctx, pc->num_user_engines, pc->user_engines);
if (pc->user_engines) {
kfree(pc->user_engines[i].siblings);
kfree(pc->user_engines);
pc->user_engines = NULL;
pc->user_engines = set.engines;
pe = &pc->user_engines[idx];
struct i915_gem_proto_engine *user_engines;