CID Clarification

[Robert Jones]

Hey Dan/Aleksander,

Thanks for the thorough information, you both are much appreciated!

Robert

On Wed, Sep 6, 2017 at 10:09 AM, Dan Williams <dcbw at redhat.com> wrote:
> On Wed, 2017-09-06 at 09:50 -0700, Robert Jones wrote:
>> Hello,
>>
>> I've done some skimming of the list archives and was hoping to get
>> some clarification on the use of client ID (CID). My general
>> understanding is that a CID refers to an instance of qmicli and it's
>> particularly important to use the "--client-cid=[CID]" and
>> "--client-no-release-cid" arguments when dealing with NAS and WDS
>> commands so the same application instance that is maintaining the
>> network connection descriptors is called.
>
> Sort of...  the "client" we're talking about is a client of a QMI
> service running in the firmware of the modem.  When you want to talk to
> NAS or WDS or DMS you ask for and get the client ID. That's your
> handle/pointer/token to a session, and if you want to continue using
> that session, you must continue passing back that client ID.
>
> Once that client ID is released, that session is closed and all its
> state gets wiped in the modem.  That's why when you're doing something
> creating a packet data session with WDS, you want to hold onto that
> client ID and pass it back the next time.  You want that session to be
> long-lived.
>
> But for one-off things like "what's the signal strength?" or "what's
> the registered network" you don't really care because they aren't long-
> lived requests.  You could certainly keep the CID around for these, but
> it's not necessary.  Internally, ModemManager does keep it around,
> because it's a long-lived process itself.  But for one-off tools like
> qmicli you do need to be aware of when not to release the CID.
>
> Dan
>
>> I'm sure I don't understand the concept entirely, could someone
>> perhaps provide more general information? Additionally, I'm
>> interested
>> in identifying the use cases where it is required to use the above
>> arguments.
>>
>> Thanks,
>> Robert Jones
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