Yo Hal! Sorry for the dealy, my inbox got full.
On Mon, 17 Jan 2022 22:41:36 -0800
Hal Murray via devel <devel@ntpsec.org> wrote:
> I think I've figured out what was going on. There are 2 stages of
> fixup. One is for the 2 digit year. The other is for the WNRO. The
> trick is that the year fixup has to let through known-bad years so
> the WNRO has the correct data to work with.
Interesting.
> If the GPS unit puts out xx20 for the year, and the pivot date is
> 2021, that shouldn't be bumped up to 2120.
Yup.
> We need 2 pivot dates, one for the 2 digit year fixup, another for
> the WNRO fixup.
More than 2, as WKRO happens every 1024 weeks.
> We need to add a pivot date to the release recipe -- something to
> replace the build-date that we removed to make builds predictable.
Maybe use the latest release data? Then we still get predictable builds.
> I think I have refclcok_nema working without using any of the
> calendar stuff. It needs more testing.
Never enough testing.
> I'm a bit surprised that Eric's early code removal effords didn't
> spot the calendar code.
Few GPS had rolled over then, so not a well understood issue.
> One problem with my current code is that Posix doesn't provide a UTC
> version of mktime. Linux and BSDs have timegm. I propose we treat
> this the same way we handle the BSD string routines -- provide an
> implementation if the environment doesn't.
According to the Linux mktime() man page:
CONFORMING TO
POSIX.1-2001. C89 and C99 specify asctime(), ctime(), gmtime(), local‐
time(), and mktime().
> There is code to use the current date for the NMEA sentences that
> provide time without any date. That's GPGGA and GPGLL. Is there a
> good reason to support that?
Yes. A lot of receivers on output GPGGA, or GPGLL, and nothing else.
> Is there any GPS unit that doesn't
> support a sentence with the date or any reason not to use it?
"support" is not the issue, "default" is. ntpd does repgrogram the
receiver to what it needs.
> It's not a big deal, just some minor clutter with a few lines of
> slightly trickly code. It needs to handle the case where the GPS
> time and system time cross day boundaries. That is unlikely to get
> tested.
Just once a day...
RGDS
GARY
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