CID Clarification

[Dan Williams]

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
> _______________________________________________
> libqmi-devel mailing list
> libqmi-devel at lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/libqmi-devel