Is it ok if ModemManager process is killed AFTER network-interface is brought up and IP-Address assigned?

[Ajay Garg <ajaygargnsit gmail com>]

Hi All.

We are using Sierra's USB-to-WWAN driver on Ubuntu-14 for Sierra's MC8090 modem, and we have a requirement wherein we need to have access to the modem-serial-port (from our user-application that is).

Right now, we see that /usr/sbin/ModemManager is always connected to /dev/ttyUSB3 (which means we cannot connect to the port from our application at the same time, or even if we can, received-data will be at best inconsistent).

We are thinking of the following ::

            * Initially, let nmcli and ModemManager do their work, and let them bring the WWAN interface up.

            * Once this happens, we permanently-down the ModemManager from our application-binary, thereby freeing up /dev/ttyUSB3.

            * Thereafter, we are free to connect to /dev/ttyUSB3 from our application, thereby using features like SMS-notification (+CMTI),
              signal-strength (+CSQ), etc.

Does our approach make sense?

We will be grateful to any help.

Thanks and Regards,
Ajay