Set allowed mode to 2G, 3G, 4G not working

[Aleksander Morgado]

> > > Within the debug output I found the following line
> > > ModemManager[623]: <debug> [1550762368.321591] MBIM-powered Telit modem found...
> > > which points out, that calling
> > > if (mm_port_probe_list_is_xmm (probes))
> > > did not find the XMM support.
> >
> > It didn't find it, because the XACT=? check failed:
> > ModemManager[623]: <debug> [1550762359.960165] (ttyACM0): --> 'AT+XACT=?<CR>'
> > ModemManager[623]: <debug> [1550762360.882668] (ttyACM0): <--
> > '<CR><LF>ERROR<CR><LF>'
> >
> > So I assume the XMM support that we have in the xmm plugin isn't ready
> > to handle this specific device.
> >
> > The inability to switch modes in this device is not a bug, it's just
> > not implemented I'm afraid.
>
> Hi Aleksander,
>
> the Telit-preferred way seems to be to handle this with AT+WS46.
> I haven't checked the code in detail but based on the AT+WS46
> references in the Telit plugin I would have expected for
> ModemManager to already use it.
>

If the modem is managed with MBIM, the generic MBIM implementation is
used for the Telit modem, so no AT+WS46 based mode switching will be
done. For this kind of cases, where we have MBIM for generic control
plus AT for other features, we would need to have a
"MMBroadbandModemMbimTelit" implementation that inherits from
MMBroadbandModemMbim but then shares features with the Telit-specific
AT modem object. So, it's totally possible to do this, but needs to be
done.

-- 
Aleksander
https://aleksander.es