xHCI provides a somewhat convoluted mechanism for specifying details
of a transaction translator.  Hubs must be marked as such in the
device slot context.  The only opportunity to do so is as part of a
Configure Endpoint command, which can be executed only when opening
the hub's interrupt endpoint.

We add a mechanism for host controllers to intercept the opening of
hub devices, providing xHCI with an opportunity to update the internal
device slot structure for the corresponding USB device to indicate
that the device is a hub.  We then include the hub-specific details in
the input context whenever any Configure Endpoint command is issued.

When a device is opened, we record the device slot and port for its
transaction translator (if any), and supply these as part of the
Address Device command.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

Support low-speed and full-speed devices attached to a USB2 hub.  Such
devices use a transaction translator (TT) within the USB2 hub, which
asynchronously initiates transactions on the lower-speed bus and
returns the result via a split completion on the high-speed bus.

We make the simplifying assumption that there will never be more than
sixteen active interrupt endpoints behind a single transaction
translator; this assumption allows us to schedule all periodic start
splits in microframe 0 and all periodic split completions in
microframes 2 and 3.  (We do not handle isochronous endpoints.)

Signed-off-by: Michael Brown <mcb30@ipxe.org>

Signed-off-by: Michael Brown <mcb30@ipxe.org>

Signed-off-by: Michael Brown <mcb30@ipxe.org>