Dell rebrands modems from different vendors, including Novatel, Sierra and Ericsson. Until now we defaulted to the Novatel plugin when a Dell device was found, but then we're breaking newer MBIM Sierra Dell-branded modems, as we don't have MBIM support in the Novatel plugin.

So, we should try to improve the probing in the Novatel, Sierra and MBM plugins, so that they probe also Dell devices, and we'll then try to match via AT-probing which plugin should be handling the Dell device.

Quoting Dan:

"The case we care about for Novatel is AT-only devices.  For those, here
is a list of commands we can use to identify them and some sample
replies.  Built from the XU870 (Dell Wireless 5510), EX725, S720, E362.

We should only do this probing if the following are true:

1) The device only has AT ports; eg it does *not* have any QMI, MBIM, or
"net" ports

2) The device does *not* report LTE capabilities via ATI or GCAP

Early Novatel QMI-capable devices (like the E362) support these commands
(at$nw*) but of course we don't want to treat them as AT-only Novatel.

=======

ati1
Manufacturer: Novatel Wireless Incorporated
Manufacturer: NOVATEL WIRELESS INCORPORATED

AT+GMI
Novatel Wireless Incorporated
NOVATEL WIRELESS INCORPORATED

at$nwdegc   (GSM/UMTS only)
(non-error response sufficient)

=======

If for some reason those don't work, here are some more esoteric ones
that we could potentially use:

AT$NWHFP?   (gsm only)
AT$NWCSQ    (gsm only)
AT$NWWDIS?  (gsm only)
AT$NWERR?   (gsm only)
AT$NWCFT?   (gsm only)
AT$NWRAT?   (gsm only)
AT$NWLTIME  (cdma only)
at$nwrssi   (cdma only)"

More context in the ML:
http://lists.freedesktop.org/archives/modemmanager-devel/2014-November/001636.html