On Mon, 21 Jan 2013, Arnd Bergmann wrote:

Alan, one comment about your version: You keep maintaining the
'#if IS_ENABLED' list in the main driver, which I think can actually
get removed now.

I considered doing that.  The benefit of keeping it is that it warns 
about configs where the main driver is built but can never be used.

Still, you're right that its purpose is becoming less important.  I had 
planned to remove it when all the glue driver had been converted, but 
in fact it could be removed at any time.

 Since the base driver can be built independent of
the presence of platform glue drivers, there is no need to forbid
it any more, and the #if block will cause merge conflicts for each
patch that converts or adds another platform.

If the patches are done independently.  There are likely to be some
context conflicts anyway.

 I think we can actually
get the same results by turning the Kconfig logic around and making
the platform glue drivers 'select USB_EHCI_HCD' than depending on
it.

That's a good idea.  The Kconfig changes would have to be done 
carefully to make sure that the dependency on USB_ARCH_HAS_EHCI still 
applies to all the platform drivers.

Manjunath, would you like to send a patch to do this?

Alan Stern