[ntp:questions] PPS kit for 2.6 linux kernels?

Ulrich Windl Ulrich.Windl at RZ.Uni-Regensburg.DE
Mon Apr 16 13:08:44 UTC 2007

hal-usenet at ip-64-139-1-69.sjc.megapath.net (Hal Murray) writes:

> >Last time when I looked at it, it had no support for kernel PPS
> >("hardpps()"). That's what I also had a long time before. I haven't checked
> >recently.
> I've never understood this area.  Why do I want a hardpps in the kernel?

Do you want a user-space algrithm play with kernel time variables, and if so,

> What I want in the kernel is support to capture the information
> accurately.  That means something like reading the time when the
> PPS signal into the serial driver generates an interrupt.

Thats PPS API without kernel bind support.

> I don't see any rush to process that data.  The ATOM/PPS driver,
> for example, processes a batch of 64 samples at a time.  So as long
> as the driver can read the data out of the kernel before it gets
> overwritten, that's good enough.

You know that hardpps can work completely without a running NTP daemon? (Well,
mostly ;-)

> Maybe in the old days ntpd couldn't get enough CPU cycles on busy
> machines.  Is that a serious problem today?

If nobody needs hardpps in the kernel, why do all the people complain about
the "alpha" PPSkit? You have PPS API there, but nothing else.


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