It's fairly inconsequential, but `wined3d_texture_validate_sub_resource_idx()` sounds like something that modifies the texture. (Compare e.g. `wined3d_texture_validate_location()`.)
Perhaps, although I'm not sure how to distinguish "make valid" from "verify validity", and in the absence of other code I would typically assume the latter. Perhaps "verify" rather than "validate"?
We'd typically use e.g. `wined3d_texture_is_valid_sub_resource_idx()` or some variant on that. Perhaps `wined3d_texture_sub_resource_idx_valid()` would also work, although it's a bit more ambiguous.
Doesn't `WINED3DUSAGE_MANAGED` imply `WINED3D_RESOURCE_ACCESS_GPU`?
At the moment, but the plan is to separate the texture into CPU and GPU copies, and at the moment at least it's more convenient to mark both copies with the MANAGED flag.
If that implication is going away this probably makes sense, but yes, it would have been cleaner separate from this patch.