Delayed response to MBIM OPEN message

Ben Chan benchan at
Thu Feb 20 22:10:28 PST 2014

> I'm not sure what the problem is, as I believe we're already doing
>  what the recommendation says. The recommendation says that the
> function should expect the host to poll the device with MBIM_OPEN, and
> that is what we do: mbim_device_open() will launch a MBIM_OPEN every
> 1s until it gets a correct reply. Or, have you seen that subsequent
> MBIM_OPEN messages end up terminating the initialization process? One
> thing to do would be to increase the time between MBIM_OPEN replies;
> i.e. giving more timeout to each MBIM_OPEN message to get the reply,
> but not sure why that would help. If we increase too much the
> MBIM_OPEN message retry, e.g. to 10s or so, we would be expecting for
> the first MBIM_OPEN message to get completed, but at that time we
> don't know whether the modem accepted that message or not (and
> therefore the whole port probing would get delayed even more).
> One thing to do would be to check, with all the MBIM devices that we
> have around, whether the modem always accepts the first MBIM_OPEN that
> it gets (e.g. looking at which responses it sends back).
> Which is the device showing the weird behaviour, if there is any? Is
> this the ZTE one?

Aleksander, I'm gathering information from a few MBIM modems and will get
back to you on this.
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