* The Data Class interface of a networking device shall have a minimum
* of two interface settings. The first setting (the default interface
* setting) includes no endpoints and therefore no networking traffic is
* exchanged whenever the default interface setting is selected. One or
* more additional interface settings are used for normal operation, and
* therefore each includes a pair of endpoints (one IN, and one OUT) to
* exchange network traffic. Select an alternate interface setting to
* initialize the network aspects of the device and to enable the
* exchange of network traffic.
* Some devices, most notably cable modems, include interface settings
* that have no IN or OUT endpoint, therefore loop through the list of all
* available interface settings looking for one with both IN and OUT
I've added the loop that follows this comment to umodem.c and found
that Nokia E50 returns exactly one additional interface,
e.g. usbd_get_no_alts() returns 1. And this interface description has
id->bNumEndpoints equal to zero, so there is no IN/OUT endpoint. At all.