Wolfgang Mauerer wrote:
> Hi,
> 
> we'd like to implement a gettimeofday() mechanism that works
> in realtime context, both from user- and kernelland. Most importantly,
> the correctins made to the wall time by the NTP protcol on Linux
> must be transferred into the Xenomai domain.

Yes, the real issue is NTP, because other than that, you can simply
implement gettimeofday in terms of clock_gettime(CLOCK_REALTIME).

This issue has been discussed several times, but never a lot. We have a
simple solution: starting with 2.4 (if I remember correctly) xenomai
provides clock_settime, so you can simply rely on clock_gettime, and
call clock_settime from time to time to resync the Xenomai clock with
Linux NTP-enhanced clock. This is not pretty, you get a drift increasing
over time, then suddenly been reset. But I guess this has been enough
for current users, until now. You control the maximum drift by how often
you call clock_settime.

Would not it be enough for your use of xenomai?

-- 
                                          Gilles


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