Re: USSD interface for ModemManager

[Dan Williams <dcbw redhat com>]

On Wed, 2010-03-10 at 08:42 -0800, Marcel Holtmann wrote:
> Hi Dan,
> 
> > > > we would like to extend the ModemManager API so that it can handle
> > > > USSD commands. The USSD API of oFono [0] looks quite nice IMHO and I'd
> > > > like to propose a similar API:
> > > 
> > > <snip>
> > > 
> > > > It is basically a copy of their API (they nailed it down) except for
> > > > GetProperties and PropertiesChanged signal which are ConnMan-specific.
> > > > I haven't had a use-case yet for the "Respond" command (my USSD
> > > > petitions are simple), but it needs to be there indeed for future
> > > > uses. Thoughts?
> > > 
> > > any reason why you are not using oFono. It is a full telephony stack and
> > > does a lot more things in the background that are mandatory. And you
> > > would not have to implement the whole USSD support all by yourself.
> > 
> > Look, I don't go around telling people why they should be using
> > NetworkManager instead of Connman or whatever.  That would just make me
> > a dick.  Which is what you're being here.
> 
> I am not talking about ConnMan here at all. So no idea why you are
> bringing this up.

Bad analogy perhaps.  I don't jump onto oFono lists and say "hey,
ModemManager supports CDMA, more devices, and has a simpler yet still
flexible API!  You should use go look at it instead!".  Which is the
objection I had.  This is a list for development about NetworkManager
and ModemManager and how to make them better.  I have no problem with
competition since that makes each project better.

Besides, Pablo works on Wader, which is a connection manager itself.  He
doesn't work on ModemManager, we just happen to share an API.  So I'm
not sure what the relevance of directing him over to oFono is anyway.

> > If you have something constructive to add to the conversation, please
> > do.  Otherwise don't post, or lets start a big ofono vs. ModemManager
> > thread somewhere else.
> 
> I have mentioned this before, at some point you need to start thinking
> from a telephony stack point of view. Especially once you start doing
> things like SMS and USSD. You have to treat your modem (even if it is a
> data card) like a phone.

Ok, what exactly do you define as a "telephony stack"?

> Maybe I phrased my question not clearly enough, but the essential part
> is that you need a telephony stack. Which one, I don't care personally
> that much. Or maybe you actually have plans to turn ModemManager in a
> full telephony stack. Then forget that I ever mentioned oFono. But then
> again, I was not asking for USSD support in the first place.
> 
> Just for fun you might wanna compare the AT init sequence of oFono with
> the one from ModemManager to see what is required. There are a lot of
> details in the SIM that will be needed even if you don't support voice
> calls.

I think we'd already covered PLMN details in a separate thread, but I
assume the other details you mean are phonebook and SMS bits?  Is the
reason oFono is using sim toolkit stuff for that functionality because
it's more conformant than normal AT commands?  Or something else?

Dan