Initial signal quality query on MBIM modems

[Dan Williams]

On Fri, 2018-01-05 at 06:57 +0000, Ben Chan wrote:
> Hi Aleksander and Dan
> 
> ModemManager currently relies on unsolicited MBIM_CID_SIGNAL_STATE
> notification to obtain signal quality updates, and it doesn't query
> the
> initial signal quality. I've observed that some MBIM modems issue a
> MBIM_CID_SIGNAL_STATE
> notification only when there is a notable change in RSSI. The signal
> quality may remain at 0 for quite some time. It's more noticeable
> when
> simply restarting ModemManager after the modem has been initialized
> and
> enabled once.
> 
> We could simply enable periodic signal quality polling on an MBIM
> modem,
> but that's less ideal as it may unnecessarily wake the modem up from
> USB
> selective suspend (unless we use a much longer polling period).
> 
> I'm thinking about letting ModemManager issue an initial
> MBIM_CID_SIGNAL_STATE query when it enables MBIM_CID_SIGNAL_STATE
> notification.  Does that sound reasonable to you. If so, I'll submit
> a
> patch.

Sounds OK to me.

Dan