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

[Jarosław Bielski]

Hi Aleksander,

thanks for your quick answer. As you have written the modem has set
capabilities gsm-umts and lte by default. I have changed current
capabilities to gsm-umts only and after that there is available a set of 6
mode combination to set. Unfortunately some combination is not allowed to
set (setting 2g only causes Core.Unsupported error) and if modem is
configured to use 2g|3g only the device still reports that it is using 4g
connection (modem has small LCD showing current modem/connection status). I
am now confused about setting current network mode on the interface.

A person from AT&T support gives me a feedback that the network mode might
be changed using AT!BAND command, I have found that another command
AT!SELRAT might be used to manage that (from MM Sierra legacy plugin).
Unfortunately the 340u modem is not supported by Sierra legacy plugin, so I
had asked you how to patch the plugin (allow to send AT command from
application or overwrite set_allowed_modes method) to make setting mode
working with Netgear modem.

I am not an expert in cellular technologies, so I would be very grateful
for any tips. I have attached output from mmcli tool.

Best regards,
 Jaroslaw Bielski

2016-04-03 12:58 GMT+02:00 Aleksander Morgado <aleksander at aleksander.es>:

> 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
>
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# mmcli -m 0

/org/freedesktop/ModemManager1/Modem/0 (device id '95786471063687f89a4e6d96b6f0d0d97ba62098')
  -------------------------
  Hardware |   manufacturer: 'Sierra Wireless, Incorporated'
           |          model: 'AirCard 340U'
           |       revision: 'NTG9X15C_01.13.12.13 r18963 ntgrbc-fwbuild1 2014/05/26 12:30:18'
           |      supported: 'gsm-umts
           |                  lte
           |                  gsm-umts, lte'
           |        current: 'gsm-umts'
           |   equipment id: 'xxxxxxxxxxx'
  -------------------------
  System   |         device: '/sys/devices/platform/ehci-brcm.0/usb1/1-2'
           |        drivers: 'GobiSerial driver, qmi_wwan'
           |         plugin: 'Sierra'
           |   primary port: 'cdc-wdm0'
           |          ports: 'ttyUSB1 (at), cdc-wdm0 (qmi), wwan0 (net)'
  -------------------------
  Numbers  |           own : 'xxxxxxxxx'
  -------------------------
  Status   |           lock: 'sim-pin2'
           | unlock retries: 'sim-pin (3), sim-pin2 (3), sim-puk (10), sim-puk2 (10)'
           |          state: 'disabled'
           |    power state: 'on'
           |    access tech: 'unknown'
           | signal quality: '0' (cached)
  -------------------------
  Modes    |      supported: 'allowed: 2g; preferred: none
           |                  allowed: 3g; preferred: none
           |                  allowed: 2g, 3g; preferred: none
           |                  allowed: 2g, 3g; preferred: 2g
           |                  allowed: 2g, 3g; preferred: 3g
           |                  allowed: 2g, 3g, 4g; preferred: none'
           |        current: 'allowed: 3g; preferred: none'
  -------------------------
  Bands    |      supported: 'dcs, egsm, pcs, g850, u2100, u1900, u850, eutran-ii, eutran-iv, eutran-v, eutran-xvii'
           |        current: 'u2100'
  -------------------------
  IP       |      supported: 'ipv4, ipv6, ipv4v6'
  -------------------------
  3GPP     |           imei: 'xxxxxxxxx'
           |  enabled locks: 'sim'
           |    operator id: 'unknown'
           |  operator name: 'unknown'
           |   subscription: 'unknown'
           |   registration: 'unknown'
  -------------------------
  SIM      |           path: '/org/freedesktop/ModemManager1/SIM/0'

  -------------------------
  Bearers  |          paths: 'none'


# mmcli --version

mmcli 1.4.12
Copyright (2011) Aleksander Morgado
License GPLv2+: GNU GPL version 2 or later <http://gnu.org/licenses/gpl-2.0.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.