I wrote this a while back, finally debugged it.  This covers
some functionality that 2.5 newly demands of all HCDs:  control
requests can be queued.  (Example:  a user mode driver can talk
on one interface, and a kernel mode one can talk on another,
no need to handshake about who can make control requests.)

The good news is that all the HCDs seem (light testing) to do
the right things ... until some of the requests (intentionally)
trigger routine faults (like protocol stalls) which the HCDs
need to recover from.  At that point, uhci-hcd started acting
confused (it's got newish queueing code); details will come
separately.  The other two HCDs acted fine.  I had expected more
trouble there, maybe it'll show up later on.