[ntp:questions] Re: Please demistify the SHM driver

Jonathan Buzzard jonathan at buzzard.org.uk
Tue Sep 16 21:40:08 UTC 2003

In article <3F673353.A3E8E61F at udel.edu>,
	"David L. Mills" <mills at udel.edu> writes:
> Jerome,
> There is ample information in the NTP documentation on how to write a
> reference clock driver and ample examples of practical implementations
> in the driver collection. There is no need to layer another interface on
> the SHM driver and much easier to maintain and debug if you do not. See
> also the pages on debugging reference clocks.

The problem with the documentation is that it suffers from the old
written by those that wrote it disease. No criticism is intended
or implied here, but it does mean that it is not as easy as it
could be for a complete newcomer.

> From this and other recent discussions in this group, it seems this
> documentation is either overlooked or ignored as being TMI. It could
> well be that an existing driver has all the features you need or could
> be easily modified for that purpose, in which case the explosion in
> drivers could be better contained. This has been done for the TrueTime
> and Spectracom drivers and should also be the case for all NMEA drivers.
> If a little twitch is necessary for an otherwise generic driver,
> consider using bits in the mode member of the interface structure.

The again there are some dirt cheap GPS devices on the market now
that probably don't even talk anything close to NMEA.


Jonathan A. Buzzard                 Email: jonathan (at) buzzard.me.uk
Northumberland, United Kingdom.       Tel: +44 1661-832195

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