[ntp:questions] Hints to write a clock driver

Dave Hart davehart at gmail.com
Sun May 31 19:17:33 UTC 2009

On Sun, May 31, 2009 at 5:18 PM, Juergen Beisert <jbeisert at netscape.net> wrote:
> Another question: How does the time flow works? I read
> the "refclock_hopfpci.c" clock driver, as it also does not use a serial
> device. It does something in "hopfpci_poll" (struct refclock.clock_poll).
> But the comment of this function (and in all the other implementations I
> found) is: "called by the transmit procedure". ????? Will this function be
> called periodically (by ntp)? Or does the clock driver trigger something to
> let it be called?

It is called once per polling interval, which for a refclock is
typically either 64s (default) or 16s (minpoll 4 on the server
127.127.t.u line).  If you want to be called once per second, there's
a relatively new timer callback you can set in struct refclock, at
least with current -dev (4.2.5).

Dave Hart

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