Sierra Wireless EM7455, MBIM connect

[Fabian Schörghofer]

> So you'd better make sure at least one process is keeping the
> /dev/cdc-wdm0 open while you are in an MBIM session (i.e. between MBIM
> OPEN and MBIM CLOSE).  That's the way you inform the driver that you are
> in a session.  I recommend using the proxy for that, but it doesn't seem
> to be straight forward with the mbim-network script.  Another
> alternative, which I use with e.g. umbim, is simply cat'ing to the
> device in another terminal:  "cat >/dev/cdc-wdm0".
>
> (note that you should not *read* from the device, because only one
> process can read - and you want that process to be mbimcli)

This does not sound very reliable because ultimately I want to use the
device on a device where only umbim is available. But I think I am
little spoiled here, my current modem the E3372 is very easy to use
with just sending AT to connect, then DHCP'ing to get the IP. (And the
Huawei Ethernet driver tells you when you disconnect because you'll
lose the IP from the interface) But I don't need to tell you that. :)

Are there less problems with QMI? I have only tried connecting, but
uqmi did not produce any result from a short test, but the qmi mailing
list would be better for this I guess.
With less problems I mean that I don't need to keep track of sessions
and such stuff. The current situation with mbim reads like that I can
enter a deadlock easily where I would have to powercycle the device.