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Date:      Mon, 28 Jul 1997 21:55:21 +0200 (SAT)
From:      John Hay <jhay@mikom.csir.co.za>
To:        bde@zeta.org.au
Cc:        freebsd-bugs@hub.freebsd.org
Subject:   Re: kern/4112: Re: PPSCLOCK kernel diffs
Message-ID:  <199707281955.VAA14196@zibbi.mikom.csir.co.za>
In-Reply-To: <199707280830.BAA17961@hub.freebsd.org> from Bruce Evans at "Jul 28, 97 01:30:01 am"

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>  
>  >	2nd, the lack of a event serial number
>  >	makes it impossible to detect extra or missing pulses.

I'm to blame for this. At the time I submitted the code I did not
know about the ppsclockev structure. If I had known I would have
used that.

>  
>  >	The current layout has a new include file, sys/ppsclock.h.
>  >	It might be a better idea to move the contents of this file
>  >	into sys/ttycom.h and rename the two new ioctls so they
>  >	fit in with the other TIO* ioctls.
>  
>  Do you want the whole LBL copyright on the merged version?

We should not take the decision to move it to ttycom.h lightly. The
xntpd code check for ppsclock.h, so if we change that we will have
to teach xntpd about it. Not that it is impossible, it's not too
difficult to get changes back to the xntpd people, but if we can
avoid incompatabilities, we should think about it carefully.

>  John Hay tried calling hardpps() from siointr1().  I don't like this,
>  because hardpps() is probably too slow on slow machines.
>  

I have code where I change the original hardpps() function to softpps()
and then create a new hardpps() that only store the timestamp and usec
values and set a flag. Then I call hardpps() from hardclock() if the
flag is set. I have tried to put it inside the 1 second if, but it did
not work too well. Outside of it it seemed to work much the same as calling
hardpps() directly from sio. Will that help Bruce?

A last thing. I feel the same way as Craig. On the machines that I use
PPS_SYNC, I just want the best time I can get. I don't use there serial
ports for anything else. Actually those machines is doing almost only
time.

John
-- 
John Hay -- John.Hay@mikom.csir.co.za



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