Re: [gpsd-dev] PPS and privilege-dropping

[Gary E. Miller]

Yo Eric!

On Thu, 17 Oct 2013 22:26:10 -0400
"Eric S. Raymond" <address@hidden> wrote:

> > Well, there you do.  Nothing to do with ntpshm.c.  I guess I should
> > look at that as it is likely broken like the rest of current PPS.
> 
> The rest of current PPS is *not* broken.  I can build it and see it
> running live on the GR601-W and on both USB and parallel ports on the
> TCX0.  You're gaving some kind of strange port problem with headers,

Well, for me, it is broken.  It does not build for me and there are
newly introduced bugs.  Gentoo is probably more plain Unix than the
Ubuntu that you run.  Worse yet there were obvious syntax errors in
code you added that you did not compile.   No C compiler will compile
code with missing semicolons at the end of statements. I hope as part of
this precess we get your understanding to where you can see the
problems. It was not broken a bit ago.

> but there is no call to talk as though the code is a pile of wreckage.

Actually, you are the one that called it a swamp (at the top of
the file), which I do not agree with.  I have never used the word
wreckage, but now that you mention it, the last few days patches fit
that description.  Changing code you can not test because you do not
have KPPS on your host is a bad idea.

Please tell me you have KPPS in your system before touching KPPS code
again.

> > Can you point me to a filename/?
> 
> ship_pps_drift_message() in gpsd.c.

Ugh.  That is seriously broken in more than one way.  It explains
some errors I have been seeing but had not tracked down.  Let's get PPS
so it builds again and then I will fix that too.  How about you move
that to ntpshm.c so it is obvious that it is a non-thread safe function
in a thread. Then I'll make sure it is one reporting the right data and
two doing it in a thread safe manner.

> > > Can I talk you into drafting a HOWTO on time-nuttery with GPSD to
> > > be included in the documentation?  Just dump your brain; I'll
> > > polish the formatting and language and then you can check my
> > > edits.
> > 
> > See the current sections "USE WITH NTP" and "USE WITH CHRONY" in the
> > current gpsd man page.
> 
> I already had the thought that most those sections of the manual page
> should move to this document; they've always been a bit out of place
> where they are.

Agreed.

> >                 A proper HOWTO might include how to setup ntpd or
> > chronyd, but that is slightly out of scope for gpsd.
> 
> Out of scope for the gpsd man page, but in scope for this document.

OK.

> > > A brief tutorial on how to choose NTPd offset parameters would be
> > > good to have in the HOWTO, too.  Basically I want this to be a
> > > primer for the relatively ignorant - like, er, me.
> > 
> > One could argue that is out of our scope as it is in the ntp.conf
> > file.  Basically you get several good chimers and adjust fudges
> > until they all agree.  From what I can tel no one really does it
> > right.
> 
> Nobody does it right because the few of you who know the black magic
> have never documented it.  So let's *fix* that, dammit.

The problem is that it is all any time-nut needs and it has never been 
clear what it is that a non-timenut does not get.  That is why I always
welcome people new to something to say what the doc lacks.

BTW, there was an article on this years ago in Linux Journal that was
well written.  We should get a copy of that to look at.
  
RGDS
GARY
---------------------------------------------------------------------------
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97701
        address@hidden  Tel:+1(541)382-8588

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