Re: [info] modem data disconnection

[Denis Kenzior <denkenz@gmail.com>]

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Hi Mylene,

On 07/21/2015 06:31 AM, Mylene JOSSERAND wrote:
> Hi everyone,
>
>
> I have some questions about ofono and the data disconnection.
>
> With debug information, after that my modem is online (connected to network via ppp0 interface), when I go back to offline (by setting online property to false), I can see that the modem network connection is down with :
> ofonod[1039]: Modem: < ~\377}#\300!}%}#} }$\205r~
>
> and PPP interface is removed :
> ofonod[1039]: udevng.c:remove_device() /sys/devices/virtual/net/ppp0
>
> I searched how ofono stops the modem connection, with escape sequence for example, but ofono does not seem to use it during offline sequence.
>

In this case the ofono_gprs_context atom is being created in post_online 
state.  Since you go offline, the modem goes back to post_sim state and 
any atoms created in post_online() are destroyed.  E.g. the atom's 
remove() method is called.  This removes all PPP processing from the 
chat and forces it back into AT command mode.

There was a similar thread recently about SIM Removal on HE910 
exhibiting similar behavior.  In that case the modem went back to 
pre_sim state, so all post_sim and post_online atoms were destroyed.

> How does ofono handles it ?

Solution is to put gprs_context creation into pre_sim on modems that 
reply to CFUN=4 or equivalent before sending the final PPP frame.

> How ofono (or gatppp, maybe ?) puts the modem network connection down (if it does) ?
>

oFono detects PPP end-of-session frames as well as the NO CARRIER result 
code.  See gatchat/gathdlc.c new_bytes() and 
g_at_hdlc_set_no_carrier_detect()

Regards,
-Denis