Re: [PATCH 3/5] gemalto: gprs: support automatic context activation

[Denis Kenzior <denkenz@gmail.com>]

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Hi Sergey,

>> Are you sure you don't want to wait until swwan_cb to return success to the
>> core?  AT^SWWAN can still fail...?
> 
> AT^SWWAN command is yet another way to activate a PDP context. AT commands
> spec for this modem is a bit vague about SWWAN details, but according to
> other materials from Gemalto as well as my experiments, this command
> activates internal DHCP server, so DHCP client can be started for modem
> USB ethernet interfaces. Based on my observations, SWWAN command does
> not return until DHCP flow is completed.

Ugh.  I'd 'window.throw(modem)'...

> 
> So the idea is to send SWWAN command to modem and make it possible to
> start DHCP flow right away. I assume that I need both things: mark
> interface for DHCP and signal success to the core. Callback swwan_cb is

So the problem with this is that you've now blocked the app/modem port until 
that DHCP negotiation happens.  Maybe it does, maybe it doesn't.  It is less 
than ideal to depend on some external component; there are frequently situations 
where people would be running without ConnMan for example.

> supposed to handle the case when SWWAN command fails: mark context as
> deactivated and let oFono proceed with further connection attempts.
> 

Another thing to consider is to just run dhcp yourself.  ell has had a DHCPv4 
client for a while now.  So you could just run l_dhcp_client to obtain the 
address and signal it to the core, leaving the app port in a known state...

Or better yet, don't use SWWAN if you can help it...

<snip>

> Sure, I can add a comment. What whould be better: to add a comment in
> driver or to write a more detailed commit message ?

Given how unusual this behavior is, I'd add a comment directly in the code.

Regards,
-Denis