Re: UBLOX and NTPD

[Gary E. Miller]

Yo Joseph!

On Thu, 21 Mar 2024 09:21:41 -0500
Joseph Beissel <joebeis64@gmail.com> wrote:

> > Yes, good, not great.  UBX is a richer protocol than NMEA 0183.  
> 
> If you have a legacy product that has been designed to use NMEA,
> there is really no reason to throw it all away to move to UBX.  I
> agree it is a much richer protocol.

You misunderstand.  The receiver is question is a u-blox receiver,
but is running it in NMEA mode.  Sometimes.  Sometimes in u-blox mode.

> > I am also curious,  but without the newer logging, nothing more I
> > can say.  It was situations similar to this one that lead to the
> > newer logging.  
> 
> Well I found out what is causing my problem.  The code makes
> ASSumptions about running in a test harness.  It ASSumes that when
> you have a sourcetype that is a "source_pty", you are running in a
> test harness.

It does behave differently.  It has to, because pty's do not support the
same ioctl() as tty's. Things like TIOMCIWAIT thst time uses are not
present. But it does not assume it is a in a test harness.

> In that case the ntpshm_link_activate() method bails
> and does not set up the thread that ultimately updates the shared
> memory segments.  That is too bad.

No intentional, because time from pty is not up to NTP needs.  See
above.

> You weren't clear on what openpty does and kept asking why I use a
> symbolic link.

And I still don't know why...

> We call openpty to create a pseudoterminal.  Using
> openpty grabs one of the available pseudoterminals (/dev/tty/#)..
> This could change based on what is running on the box and how they
> are being used.  Using openpty allows flexibility.  However to hide
> the fact that the  pseudoterminal can and most likely will change, we
> hide that behind a symbolic link that our software uses.

gpsd does not let things "hide" behind a symbolic link.

> This
> isolates the user from knowing anything about the pseudoterminal.

The way you isolate the user is with a startup script.

RGDS
GARY
---------------------------------------------------------------------------
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
        gem@rellim.com  Tel:+1 541 382 8588

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    "If you can't measure it, you can't improve it." - Lord Kelvin

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