RE: [PATCH 4/4] isigen: make number of PDP contexts configurable

[Marcel Holtmann <marcel@holtmann.org>]

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Hi Mika,

> > why to do you bother making this a configurable option? What isthe
> > benefit here?
> 
> The maximum context count is a compile time option for the ISI modem. Having this option in oFono makes it possible to optimize the APE side resource usage instead of overallocating drivers and contexts. Not a huge benefit, I guess, but the cost is not huge either.
> 
> Not a big deal, though. I'll try to see if the context limit could be probed somehow.

if it can be probed from the ISI modem that would be perfect.

> > Personally I think that always enabling 4 context if the hardware
> > supports it should be enough. If you do support more then just enable
> > more all the time. There are no real resources used in context of ISI
> > anyway. The AT command based modems have a different problem since for
> > most of them we need an extra TTY/DLC and an extra GAtChat object, but
> > ISI does not have that problem.
> 
> I don't see the difference. The AT modem resources should be allocated dynamically as well, at context activation time. (Maybe that's the case already, I didn't really check.) In any case, I believe oFono has to allow things like external AT command processors and vendor specific modem tools to access the TTY's directly bypassing oFono. This means the mux channels should not be preallocated.

That is sort of a dream world. AT command based modems where you need a
TTY/DLC for every active GPRS context are not cheap. It is not a crazy
waste of resources, but it is some kind of waste.

Regards

Marcel