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

[Denis Kenzior <denkenz@gmail.com>]

[-- Attachment #1: Type: text/plain, Size: 1913 bytes --]

On 11/11/2010 02:16 AM, Mika.Liljeberg(a)nokia.com wrote:
> Hi Marcel,
> 
>> 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.
> 

The gprs context structure is about the size of 5 pointers, so there's
not much to be saved here.  If you're worried about space usage of the
isi specific data, you can always allocate it during the activation stage.

>> 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.

Hah, I know some people who vehemently disagree ;)  Of course I'm not
one of them...  Strictly speaking what you say is possible even with
today's architecture, however almost no AT modem we have supports more
than about 3-4 contexts.  So doing this to save 300-400 bytes / context
is simply not worth it at this point.

Regards,
-Denis