GPRS support for Ofono

[Rémi Denis-Courmont]

----- Message d'origine -----
> Again, I don't see a point of exposing this to the user.  Worst case we can
> always add intelligence / heuristics to oFono to attempt re-attaching
> periodically.  We have to solve this for all modems, since there are no such
> 'auto-attach' semantics in 27.007.

If it comes to the question of usefulness, I find the current attach/detach to be even more useless than always-attach/demand-attach.

AT modems will attach automatically when a context is activated, so do ISI modems (when adequately configured), and foobar modems could always emulate it (from inside their context API).

I agree that auto-attach is not of much use to end-users, for the exact same reason that attach is not very useful. But it is apparently of use to network operators at least.

> One strategy you can use today is to just activate auto-attach when the driver
> is asked to attach and force a detach when the driver is asked to detach. 
> This is essentially the behavior of most AT command modems.

Sure. ISI modems can do that too. And I argue it makes manual attach/detach even more useless than auto-attach.

I'd note that flight mode requires deregistering from the network as a whole, not just detaching from GPRS anyway.

So I can implement the current attach/detach logic, but it seems not very pertinent to me as an API.

> I have two suggestions here:
> 1. Lets make it work first, we can then make it work better.
> 2. Can you describe these optimizations and suggest how the API/behavior can
> be changed to take advantage of them?

We just need to know if the core or the upper-layer application intends to activate a context. It is a boolean flag hint to Attach basically.