On Thu, 22 Dec 2005 00:18:33 +0100
Simon Richter <[email protected]> wrote:
> A good ntpd will adjust the speed rather than write to the clock; the
> ntpd shipped by most distributions can already handle multiple time sources.
Yes, but there's the kernel who writes to the clock,
for example http://lxr.linux.no/source/arch/arm/kernel/time.c?a=arm#L103 .
> > later. The /dev/rtc interface only supports one clock.
> > It can either be extended to have /dev/rtcX or we
> > can extend the sysfs one to allow clock updating.
>
> /dev is the way to go IMO. As far as I've understood sysfs, it carries
> meta information about devices and drivers only, the actual
> communication then happens through device nodes still.
Ok. We can use dynamic device numbers and go for the /dev
interface.
>
> > NTP mode could then be adjusted to update one or more
> > of the rtcs. Maybe each RTC could have an attribute
> > (let's say /sys/class/rtc/rtcX/ntp) which tells the
> > kernel whether to update it or not.
>
> That's entirely a userspace thing. What the userspace needs to know from
> the kernel is whether the clock is writable and whether its speed can be
> adjusted.
agreed. there are are also some variables of interest in
http://lxr.linux.no/source/include/linux/timex.h?a=arm#L188
some of them may be usefully exported in sysfs.
--
Best regards,
Alessandro Zummo,
Tower Technologies - Turin, Italy
http://www.towertech.it
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