USB serial device naming

[Hans Petter Selasky]

Hi,

Maybe you can make PR on the issue and assign it to USB. Currently there is no 
way of knowing which /dev/cuaUXXX belongs to which USB device. Probably we can 
add the USB bus and address number as a part of the device coordinates. So 
that /dev/ugen1.1 only creates /dev/cuaU1.1.xxx entries. And then we can also 
remove the current unit number allocation structure I guess, if we use:

/dev/cuaU1.1.<iface_number>.<optional_sub_modem_unit>

The only problem is: Will we break any existing applications?

The second problem was that the USB attach event was generated before the 
modem was probed and the umodem and other modem drivers do not provide any 
information about their USB address in the pnpinfo. This can be fixed.

Old pnpinfo:

dev.ums.0.%pnpinfo: vendor=0x0 product=0x0 devclass=0x00 devsubclass=0x00 
sernum="" release=0x0200 intclass=0x03 intsubclass=0x01

Suggested new pnpinfo (which is available from devd.conf I guess)

dev.ums.0.%pnpinfo: vendor=0x0 product=0x0 devclass=0x00 devsubclass=0x00 
sernum="" release=0x0200 intclass=0x03 intsubclass=0x01 bus=1 addr=2 
ifaceidx=0

What do you think?

--HPS