[MM - plugin] Network mode change support on Netgear AirCard 340u.

[Aleksander Morgado]

Hey,

>
> I am trying to add support for changing network mode (2g, 3g, 4g) on
> Netgear AirCard 340u (1199:9051) cellular modem, currently without a
> success.
>
> Please find the following versions of libraries and ModemManager, that I
> am using:
>  - libqmi-1.12.8
>  - libmbim-1.12.2
>  - ModemManager 1.4.12 (*)
>
> (*) - I have applied patches adding sierra legacy plugin from ubuntu
> package available at:
>
> https://launchpad.net/ubuntu/+archive/primary/+files/modemmanager_1.4.12-1ubuntu1.debian.tar.xz
>
> The modem is handled by Sierra plugin (QMI modem + AT serial port) which
> does not allow to manage network modes (only one combination 2g,3g,4g is
> available). I have already checked that network mode management on the
> dongle is possible using SELRAT AT command (the same method as legacy
> Sierra plugin).
>

The QMI based implementations need 2 different steps to change network
modes currently: first capabilities, then modes. If you only have the
2G+3G+4G combination, that means you're in the "gsm-umts+lte"
capability combination. Try to change the capabilities to "gsm-umts"
onlt, and once that is done, the device may power cycle and let you
change to other modes like "2G+3G with 3G preferred".

The additional power cycle isn't always needed, but we do enforce it
when changing capabilities, because the change may require
adding/removing DBus interfaces (not in this case, though).

I believe this blogpost is still relevant:
https://sigquit.wordpress.com/2013/06/03/changing-modes-and-capabilities-in-modemmanager/

-- 
Aleksander
https://aleksander.es