Originally Posted by hawhill
... I think it is only recognizing one USB bus, and I think that would probably be the host-mode bus that's used for e.g. driving the 3G modem (at least on older Kindle models, that was the case). Something must be triggered to present the other USB interface as a Host, too, so the fsl-ehci driver could care for it.
That seems to agree with what I found in an old MobileRead thread, where they mostly decided that the built-in USB gadget drivers were manipulating the INTERNAL USB instead of the external USB port. In which case things become even MORE "non-trivial", requiring solutions similar to what they used to get this stuff working on the Nook Simple Touch.
The "something must be triggered" is probably what the custom Nook Simple Touch program did to configure the external port for OTG. That is why I added that program to the (non-trivial) list of things that may be needed in my earlier post.