Messages in this thread | | | Date | Thu, 17 Aug 2006 13:01:10 +0200 (CEST) | From | Roman Zippel <> | Subject | Re: [NTP 8/9] convert to the NTP4 reference model |
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Hi,
On Thu, 10 Aug 2006, linux@horizon.com wrote:
> The original NTP kernel interface was defined in units of microseconds. > That's what Linux implements. As computers have gotten faster and can > now split microseconds easily, a new kernel interface using nanosecond > units was defined ("the nanokernel", confusing as that name is to OS > hackers), and there's an STA_NANO bit in the adjtimex() status field to > tell the application which units it's using.
BTW this patch didn't add the STA_NANO bits yet, as that requires changes to <sys/timex.h> and a recompiled ntpd, so the values are still in usec. It's not difficult to change/add, but one has to be a little careful about compatibility.
> The current ntpd supports both, but Linux loses some possible timing > resolution because of quantization effects, and the ntpd hackers would > really like to be able to drop the backwards compatibility code. > > Ulrich Windl has been maintaining a patch set to do the conversion for > years, but it's hard to keep in sync.
I think you refer to the PPSKit? Well, the first step to integrate it properly is done. Ulrich took the reference code rather unmodified, which has a rather strong emphasis on weird portability (one only has to look at l_fp.h to know what I mean), which is not really acceptable in the kernel. Its ioctl API probably should be converted to sysfs, so there is still some way to go.
bye, Roman - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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