mbim-proxy vs mbimcli --no-open/--no-close

[Greg Suarez]

On Fri, Jul 11, 2014 at 6:51 AM, Aleksander Morgado <
aleksander at aleksander.es> wrote:

> On Fri, Jul 11, 2014 at 1:42 PM, Bjørn Mork <bjorn at mork.no> wrote:
> >> One thing we didn't think about is how the mbim-proxy should handle
> >> --no-open or --no-close actions performed by the mbimcli command line
> >> interface.
> >>
> >>  * When the --no-close option is used by mbimcli, it won't send a last
> >> MBIM Close request to the modem before exiting.
> >>
> >>  * When the --no-open is used by mbimcli, it won't send an initial
> >> MBIM Open request to the modem when starting (e.g. if --no-close was
> >> used in the previous action).
> >>
> >> Now, when using the proxy, it will send an explicit MBIM Close request
> >> to the device when all clients have been disconnected from the proxy,
> >> which prevents the usage of --no-close. How can we best handle this
> >> situation?
> >>
> >> One option would be to let the proxy keep an 'open count' value,
> >> depending on the open/close requests coming from the clients, and only
> >> if the open count drops to zero it will send the MBIM close. One
> >> problem with this approach is that if e.g. we get ModemManager
> >> segfault unexpectedly it won't send the MBIM close, so an
> >> open-reference will be lost. Not sure if this is a big issue, though.
> >>
> >> What do people think?
> >
> > I don't think there is any way you can make CLOSE work with the proxy,
> > so you might as well just do an OPEN when the proxy starts and a CLOSE
> > when it exits.
> >
> > The only reason a client has to close a session is to ensure that the
> > modem is reset to some default initial state.  This is impossible to
> > gurarantee with the proxy, because other clients may depend on the
> > current state.  IMHO it is better to make the behaviour predictable by
> > never honouring a CLOSE request than to implement some scheme to allow
> > the last client to issue a real CLOSE.
> >
> > And it is easier as well :-) No reference counter and no problems with
> > crashing clients.
>
> That is indeed a good approach... and much easier. Greg, what do you think?
>

That sounds good, but we would have to modify the proxy so that it doesn't
exit
if there are no clients connected.

Greg
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