SMS retrieval on Telit LE910 V2 EU with MBIM

[Aleksander Morgado]

Hey,

>  I'm looking now into SMS support on LE910 modem running in MBIM mode.
> This is on MM 1.7.991 and libmbim 1.16. It seems sending messages
> works out of the box but retrieval has some issues.
>  I found that the MM doesn't receive MBIM notifications when new SMS
> come, i.e. no MBIM_SMS_READ_INFO is sent by the modem. It seems though
> it is correct according to MBIM specification for the modem to only
> send the notification when class 0 messages come (i.e. not for normal
> SMS - if I understood this correctly).
> 

The way I read the MBIM docs, is that there are two ways to report new received SMS messages:
  * For class 0 (flash) messages, MBIM_CID_SMS_READ are sent. The SMS comes in the MBIM indication itself.
  * For non-class 0 (standard) messages, MBIM_CID_SMS_MESSAGE_STORE_STATUS notifications are sent, the SMS is stored and must be read with an additional MBIM request specifying storage index.

I've pushed a minor update in MM to fix the names of the functions in the logic in charge of this, because we were actually assuming the opposite:
https://cgit.freedesktop.org/ModemManager/ModemManager/commit/?id=6c37488d4ebbbb2afdefce193e6fb4070cde8ab3

>  In that case is there a way to make ModemManager poll the list of
> SMSes stored on the device to update it's internal list? (Or is it
> possible to make MM aware of new SMSes otherwise?).
> 

As said, MM should receive new SMS via those 2 methods described above.

>  The other issue I found on that particular modem is that it seems
> only SMSes stored on SIM card are visible via MBIM. I.e. AT+CPMS="SM"
> has to be set first and only then the messages are seen by
> ModemManager. But since it seems this setting is stored on modem's
> flash it's enough to set it once with AT commands and then
> ModemManager is able to get the list of SMS stored on SIM during the
> start-up.
> 

This is one of the limitations of the MBIM protocol. There is no definition of multiple SMS storages in the MBIM protocol, it only talks about the "indices" where the SMS messages are stored. So, in ModemManager we assume the only available storage is the "mixed" MT storage (SM+ME). We could provide an additional "AT fallback" mechanism to query and manage SMS storages via AT before listing the messages with MBIM, but not sure how clean that logic could be with the different MBIM firmware implementations around...

-- 
Aleksander
https://aleksander.es