Re: [PATCH v4 3/5] cfg80211: Accept multiple RSSI thresholds for CQM

[Andrew Zaborowski <andrew.zaborowski@intel.com>]

On 8 February 2017 at 13:32, Johannes Berg <johannes@sipsolutions.net> wrote:
>> > I think it would make sense to unconditionally apply the hysteresis
>> > to low/high, i.e. always set
>> >  low = low - hyst
>> >  high = high + hyst
>> >
>> > so that you get "sticky" ranges once you're in them?
>>
>> Yes, maybe that's better, I guess I want to avoid just adding a lag /
>> delay in reporting changes that are not due to measurement error or
>> temporary.  Could also do something in between, e.g. use "low - hyst"
>> if signal is close to low, otherwise just "low".
>
> That's sort of what you had, but except for the precise definition of
> "close", no?
>
> Actually, no, because you used "last - hyst" rather than "low - hyst"
> it's different. I think we can live with checking if it's close, say
> setting to "low - hyst" when it's within low + hyst - that avoids the
> problem I outlined above and gets a bit more responsiveness, I guess.

I sent a version with this logic but came up with values that would
still cause the continous events as in your example, specifically with
a hyst of 3 and the reported RSSI values jumping between -51 and -47.
This could be avoided by changing operators between "less than" and
"less or equal" but I eventually sent a version with the "sticky"
ranges you suggested, I think that is just as good.

Best regards