[RFC] Signal interface: threshold based setup

[Aleksander Morgado]

Hey all,

The extended signal information interface only allowed to configure a
fixed polling rate as the method to update the values reported by the
interface properties. E.g. the user could say, please update the
interface properties every 30s. But polling is far from optimal, it
drains battery, and in lots of scenarios the signal quality updates
could even be rare.

Modems also allow configuring threshold based signal quality update
reporting, so that the modem emits indications every time the signal
changes according to what we have configured. Some modems allow to say
"please notify every time the signal changes more than 10dBm w.r.t.
the last value", some others allow to say "please notify every time
the signal crosses a given set of fixed levels, e.g. -60dBm, -70dBm,
-80dBm, -90dBm".

This new API proposal tries to use the first method, with the users
providing one single value (the difference of the value between
reports) as threshold; and for MBIM devices this is fine. For QMI I
would say we can convert the user provided value into a list of fixed
levels, and use those to configure the NAS Signal Strength or NAS
Signal Info indications (with the known limitations in the amount of
levels we can propose...).

The suggested API update also introduces support for reporting channel
bit error rate measurements, in percentage, as well as configuring
thresholds for that value.

See https://gitlab.freedesktop.org/mobile-broadband/ModemManager/-/merge_requests/649

Comments?

-- 
Aleksander
https://aleksander.es