Antw: [EXT] org.freedesktop.timedate1.NTPSynchronized not signaled: rationale?

["Ulrich Windl" <Ulrich.Windl@xxxxxxxxxxxxxxxxxxxx>]

>>> Etienne Doms <etienne.doms@xxxxxxxxx> schrieb am 17.08.2022 um 12:58 in
Nachricht
<CACGcE5K6zKJjPeJDbEyMW8VM8i_9J1JtJc-8PbtwTib0HjAHTw@xxxxxxxxxxxxxx>:
> Hi,
> 
> I'm developing an application for an embedded system that needs to
> wait for proper NTP synchronization. systemd-timesyncd is running and

What's wrong with time-sync.target? Or maybe even time-set.target?

> I can read NTPSynchronized from /org/freedesktop/timedate1 using
> D-Bus. I read in the manual that this property is not signaled, and
> that I need to do some weird magic with timerfd's
> TFD_TIMER_CANCEL_ON_SET flag.
> 
> It works, but having the ECANCELLED on the read() means that something
> somewhere did clock_settime(CLOCK_REALTIME, <...>), not especially
> that I got a proper NTP synchronization. Then, I still need to query
> NTPSynchronized after, and retry the timerfd thing if it didn't switch
> to "true", which is still some kind of polling (but very unlikely,
> sure).
> 
> As a result, I'm a bit curious, what was the rationale of not simply
> signaling NTPSynchronized?
> 
> Thanks,
> Etienne