fibocom: Minimum PDP context ID

[Aleksander Morgado]

Hey,

> On 3/8/22 15:21, Aleksander Morgado wrote:
> > If I'm not mistaken, in Intel chipset based modems, CID=0 is used to
> > handle the initial default EPS bearer; i.e. the bearer that gets
> > automatically setup when the modem gets registered in the network. If
> > +GTRNDIS isn't able to handle attempting a connection over that
> > bearer, we should definitely try to use CID>=1 instead. This is
> > probably something to handle in the Fibocom plugin itself.
>
> I believe you're right that I'm looking at the default EPS bearer. What
> would be the simplest way to only use CID>=1 for Fibocom modems? The
> fibocom plugin uses the default connect_3gpp method for context
> selection, configuration etc. Is there a simple way to restrict the CID?
>

The way to restrict the CID range to >= 1 would be to subclass the
check_format() method in the MMIfaceModem3gppProfileManager, so that
it returns a "min_profile_id" equal to 1. For that, you could just
call the "parent" check_format() method, in order to use the generic
+CGDCONT=? operation, but then overwrite the "min_profile_id" you get
there (assuming you get 0) and return 1 instead in that field.

> Speaking of the default EPS bearer, should ModemManager be aware of that
> bearer somehow, i.e. list it as an active bearer object etc?
>

Yes, we could do that, definitely. There is no chance of getting the
profile id wrong in Intel-based modems I think, if they support CID 0,
that should be the one used for the initial EPS bearer.

-- 
Aleksander
https://aleksander.es