[Soekris] Net5501: USB devices & attach/detach events

[Guy F. Boyd]

 One oddity I've noticed regards the on-board USB 1.0 host interface on the
net5501 (FreeBSD RELENG_6). My tests here seem to suggest that what is described
below could be attributable to generic or obscure differences in the USB 1.0
standard and the USB 2.0 standard but I've read the standards until my eyes are
bleeding and I can find no specific references. I suppose the problem could also
be USB power level related. Someone with better bare-metal USB chops would
probably know for sure.

Seems that when a (externally powered) USB hub is attached to the on-board USB
1.0 host interface, various USB devices that are subsequently attached to the
hub do not register attach (or subsequent detach) events (via /dev/devctl).
Only devices that are attached to a hub *before* the hub is connected to the
host port will register attach events.

A small pile of hubs and new USB 2.0 multiport PCI USB host interface cards
under test in the PCI slot seem to support the previous assertion that this may
be a USB 1.0/2.0 standards difference, as devices attached/detached to a hub
connected to a PCI USB 2.0 host card do the Right Thing.

 I dont see anything obvious following /usr/src/sys/kern/subr_bus.c up via
devctl_notify() and devctl_queue_data()  to suggest that anything is broken or
missing.

I just wanted to place this into the archives and out on the Ether in case
anyone else runs into this and discovers something new about it.

Guy Boyd
Atlanta GA USA