> Point taken.  I'll try and get physical location as a locator
> for USB.  A physical location will then be a sequence of 1-5
> (there is a limit of hub depth to 5) port numbers that tells
> you how to navigate from the root to the device.

I would think that this would be better handled as a hierarchical
chain of hub attachments, just like how pci buses are managed now..

In the config file as:

   usbroot* at pci?
   usbhub* at usbroot?
   usbhub* at usbhub?
   usbdev* at usbhub?

And if you need to nail things down more:

  usbroot0 at pci?
  usbhub0 at usbroot0
  usbmonitor0 at usbhub0 port 0
  usbhub1 at usbhub0 port 1
  usbkeyboard0 at usbhub1 port 0
  usbmouse0 at usbhub1 port 1
  usbhub2 at usbhub1 port 2
  usbaudio0 at usbhub2 port 0
  usbaudio1 at usbhub2 port 1

...