How do I convert 4.5.0 driver to 4.6.0?

I have a via driver (Unichrome from last November plus patches) that 
works very well on
 4.5.0. It supports XVIDEO that the standard XFree86 driver does not 
support.

I can build and use this same driver code is a trivia patch under 4.6.0 
but xvinfo reports
that there is an XVIDEO adapters.

Looking at the diffs of the xfree86 via driver between 4.5.0 and 4.6.0 I 
seem to see that
all that changed, apart from new features, is loader stuff:

-        LoaderRefSymLists(vgaHWSymbols,
+    LoaderModRefSymLists(module,
+                 vgaHWSymbols,

Do I need to make these loader changes to get correct operation or does 
your fallback code
work correctly in all cases?

Where should I look to debug why XVIDEO is not showing up under 4.6.0?

Barry