Hi Mylene,

 >
> I looked to other modem plugins. I think I understand what the slave is thanks to that. It is the other interfaces to send AT commands, only, whereas the "main" GAtChat serves to create the PPP connection, is not it ? If I am wrong, do not hesitate to make me understand how it works.
>

Pretty much.  When we pass the chat to the gprs_context driver we set 
the slave chat.  This is needed in order to monitor certain events which 
come in via AT commands when the PPP link is active.  In effect we 
require 2 AT command ports.

On some hardware there was only a single functional PPP port, so the 
driver might need to be modified to handle that case, but it sounds like 
you don't have this issue.

> I set the slave (via "g_at_chat_set_slave") to my "Application" device and I succeeded to get 2 contexts. I activate them and it creates the PPP and QMI connections ! I still have a problem : I did not get an IP address on one of the APN connection but this is another problem (connman ?) and I will search alone for that before asking for help :)
>

Cool, feel free to send a patch for this.

IP settings are notified to oFono by the gprs_context driver.  If there 
are IP settings given, then most likely they should be obtained via 
DHCP.  Running test/list-contexts should tell you all the information 
once both contexts are active.

Regards,
-Denis