USB2 - umass problem

Hans Petter Selasky hselasky at
Wed Feb 4 02:24:56 PST 2009

On Wednesday 04 February 2009, Vladimir Grebenschikov wrote:
> On Wed, 2009-02-04 at 10:44 +0100, Hans Petter Selasky wrote:
> > > By some reason devfs semantic was changed:
> > > Instead of /dev/cuaU0.[0-2] and /dev/ttyU0.[0-2], I've get
> > > /dev/cuaU[0-2] /dev/ttyU[0-2] and! /dev/cuau1 /dev/ttyu1
> > > What is reason for such change (additional port with lowercase 'u' and
> > > U[0-2] instead of more logical U0.[0-2]) ?
> >
> > It is because we are attaching drivers per interface instead of per
> > device. A new modem unit is allocated every time we find a modem, simply
> > put. If the modem has multiple instances in an interface,
> > /dev/cuaU0.[0...] will be created. Else /dev/cuaU... .
> What about /dev/cuau1 /dev/ttyu1 ?

TTYs follow the same naming convention like the cuaUxx .

If the modem has got one modem in each interface and three interfaces:

/dev/cuaU0 /dev/ttyU0
/dev/cuaU1 /dev/ttyU1
/dev/cuaU2 /dev/ttyU2

If the modem has got three modems in one interface:

/dev/cuaU0.0 /dev/ttyU0.0
/dev/cuaU0.1 /dev/ttyU0.1
/dev/cuaU0.2 /dev/ttyU0.2

How this is configured is decided by the USB device manufacturer.


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