Re: [RFC PATCH 1/1] ublox: create only 1 gprs context

[Denis Kenzior <denkenz@gmail.com>]

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Hi Jonas,

On 03/14/2019 05:37 PM, Jonas Bonn wrote:
> ---
> 

Funny, I was looking at this code today and thought it was wrong.  Was 
going to point this out to you, but you beat me to it ;)

> Here's something that I'm having trouble understanding.  The ublox
> plugin creates 8 gprs_context atoms.  As far as I can tell, this means
> that ofono will allow it to activate 8 contexts simultaneously... right?
>

Correct.  Each context driver added to gprs allows a concurrent context 
to be activated.  E.g. if you have 2 drivers, you can activate 2 
contexts simultaneously.  Obviously you need a high speed / ppp 
interface for each active context.

> Why is the ublox plugin the only one that does this?  Do other modems
> not support multiple active contexts?  Or is this plugin wrong?

 From what I recall, ublox does claim to support multiple PDP contexts 
active at the same time.  However, I don't know how this works in 
practice as you need a unique network interface for each one.  As it 
stands today, given the udevng detection logic, this plugin is wrong.

> 
> If I were to follow the model of other plugins, the below patch would
> seem appropriate...
> 
> A bit of insight here would be appreciated.

There are drivers for USB based modems that do this properly.  See 
xmm7xxx for example.  Multiple PDP context support was added to that 
recently.

Modems that used multiplexing had support for multiple PDP contexts for 
quite some time.  E.g. plugins/ifx, etc.

Anyway, patch looks fine to me.  Let me know if you want me to apply it 
or you want to take a stab at fixing the detection logic.

Regards,
-Denis