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Re: [gpsd-dev] ntp reference clocks


From: juergen perlinger
Subject: Re: [gpsd-dev] ntp reference clocks
Date: Tue, 24 Mar 2015 19:24:24 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.5.0

Hello All,

On 03/23/2015 09:09 PM, Gary E. Miller wrote:
Yo Sanjeev!

On Tue, 24 Mar 2015 02:15:00 +0800
Sanjeev Gupta <address@hidden> wrote:

On Tue, Mar 24, 2015 at 1:25 AM, Gary E. Miller <address@hidden>
wrote:

Sadly no.  It takes as many config lines in ntp.conf as doing it as
a SHM, and provides no extra benefits.

Oh.

I was hoping that it would avoid having to calculate fudge factors,
SHM issues, etc.
Nope.  You need the exact same fudge factor either way.  It does spare
you SHM issues, but instead add /dev/ baming issues.

Due to the old style fake IPv4 naming of ref clocks, you need a link
from you GPS to /dev/gpsX.  Then the refclock last octet is the X.

Also no way to get a naked /dev/ppsX from gpsd, which is the feature I'm
working on now.
If that seems useful, I could use 'readlink()' to get the underlying 'true' device name for the communication between NTPD and GPSD. But that would not remove the need for a symlink, though it might make things easier for GPSD. Gary, what's your opinion here?

What NTPD is really missing is a standard way for IO configuration, including the device names. Not to mention baud rates and alike... But adjusting all drivers to such a new schema would be quite some work, I think.

I am all in favor of the new gpsd JSON driver, it just has a ways to
go to be better than the existing SHM driver.

At some point it would be cool if the ntpd JSON driver could poll gpsd
for time sources and auto-config, but not yet.

I downloaded 4.3.10 and am building it on a Raspberry Pi, connected
to the GR601W.  Will take a few more hours to complete :-)
Cool.  You'll note I have been adding RasPi comments to the INSTALL file.

That prolly needs to be forked, maybe: INSTALL.raspi.
Attention -- I have not yet integrated the updated driver into ntp-dev or -stable! I wanted to be sure that there are no obvious bugs in the code...

Gary, did you find anything that needs repair soon? If not, I would create a bug/featrure report and have my changes merged.

Cheers,
    Pearly



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