[OpenWrt-Devel] [PATCH uqmi] nas: add --get-plmn

Martin Schiller ms at dev.tdt.de
Thu Aug 29 03:29:57 EDT 2019

On 2019-08-26 21:12, Sami Olmari wrote:
> I think the ideology behind proto handler there is to "do whatever
> told" despite of what the state is currently,
> maybe there is a reason for such behaviour (searches some stuff from
> network etc).

There exist 2 problems in the qmi proto handler:

1. Setting the plmn to 'auto' will implicitly lead to a (delayed)
network re-registration, which could further lead to some timing
related issues in the qmi proto handler.
Let me explain this in more detail:
After successfully calling the uqmi --set-plmn (auto) command it takes
up to 5 (or maybe even more) seconds until the modem detaches from 
and start searching for new registration.

In the meantime the proto handler goes through the next steps ("Waiting 
network registration", "Start network $interface" etc.).

I hope you can see were this leads to.

This is really a problem in Roaming scenarios, where to provider maybe 
switched after the re-registration.

2. The plmn setting is permanently saved in the wwan modem:
This leads to the problem, that if you switch back from manual plmn 
to auto mode you have to set it explicitly to 'auto'.

- Martin

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