In D8582#162577, @davidedmundson wrote:

Do you think we'll need a compositor fallback?

*If* we do have a compositor fallback, then I don't see the point of a DRM specific codepath, it's not going to have any slower having a transform in painting, and will just result in one code path not getting tested.

To mostly answer my own question:

In hwcomposer, it seems we have a transform attribute on the layer.

For nested wayland we can set a transform on our wl_surface.

For FBDev or nested in X, I don't think we can. But probably don't care?

Yep. And that's why I don't want to add a compositor fallback. Doing the fallback looked quite complex when I looked at it due to multi screen.