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SubjectRe: 11 minute RTC update (was Re: Remove RTC UIP)
On Tue, 28 Mar 2006 19:21:37 -0600
Matt Mackall <> wrote:

> > > With existing NTP setups, and the kernel no longer writing to the RTC,
> > > you might have the RTC drift far enough that NTP failed to sync on the
> > > next boot. (Correct me if I'm wrong, of course.)
> >
> > That's probably true, I'm not expert on the matter. The new subsystem only
> > covers platforms that were not covered before (i.e. without external patches),
> > so that this should not impact users because the NTP update mode
> > was not working on them.
> >
> > The problem might arise when other RTC drivers (i.e. x86) will be converted
> > and deployed.
> >
> > We need a migration plan. Any suggestion?
> I guess the question then becomes: is existing userspace (ntpd)
> already doing its own updates. If so, we can schedule the feature for
> removal in the near future. If not, it may take quite a bit longer.

I think it isn't. Ideally ntpd should open /dev/rtcX and write the time,
but I'm not sure if it belongs to it or if a simple hwclock --systohc /dev/rtcX
should be used.

Obviously hwclock needs to be updated to support multiple RTCs.


Best regards,

Alessandro Zummo,
Tower Technologies - Turin, Italy

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