Originally reported at:
Please refer to the original bug report if more details are needed.
The QMI support in ModemManager is lacking support for USSD. Currently, unsupported is reported by default for every QMI modem:
iface_modem_3gpp_ussd_init (MMIfaceModem3gppUssd *iface)
/* Assume we don't have USSD support */
iface->check_support = NULL;
iface->check_support_finish = NULL;
The USSD commands are defined in the 'voice' service in QMI. If no such service is available in the modem, we could fallback to the generic AT-based implementation if possible (e.g. as with GPS).