RFC: New device filter policies

[Aleksander Morgado]

Hey!

Following the discussion regarding Debian wanting to patch
ModemManager to avoid unnecessary probing of non-modem TTYs, I ended
up preparing a branch that implements a set of "filter policies"
composed of different "filter rules".

See documentation for the filter rules here:
https://www.freedesktop.org/software/ModemManager/api/1.8.0/ref-overview-modem-filter.html

And documentation for the filter policies here:
https://www.freedesktop.org/software/ModemManager/api/1.8.0/ch03s02.html

By default ModemManager would use the "DEFAULT" filter policy, which
is equivalent to the logic we've been using in previous releases. But
these patches also allow stricter policies (e.g. the "STRICT" one)
that would not allow probing of non-modem TTYs (but may also not allow
probing of modem TTYs not covered by the default heuristics!).

This is now implemented in the "device-filter-policies" branch in my
github repo:
https://github.com/aleksander0m/ModemManager/commits/device-filter-policies

One quick test that you all may do would be to build ModemManager from
this branch and run it in STRICT mode, and see if your modems are
still completely probed and that non-modem TTYs aren't probed:
# /usr/sbin/ModemManager --filter-policy=STRICT --debug

Comments?

P.S.: didn't fully test this myself with all my modems, and in
particular, I have no idea how it will behave with bluetooth DUN
devices.

-- 
Aleksander
https://aleksander.es