I am still confused as to why people recompile their kernel to put in
the kernel PPS. Just use the regular ntp devices like shm and a program
like gpsd to run pps from userland. I have no idea what advantages the
kernel PPS provides, certainly considering the pain of recompiling the
kernel. In fact I would argue that userland is the place where you
should be doing the PPS shaping-- throwing out popcorn spikes, making
sure that the PPS is producing sensible output (eg each pulse coming one
second after the previous on, not 3ms, or something like that, which can
happen).
Ie, you do not need kernel pps to make use of pps.
I think you are correct in your final statement, but my understanding
(albeit limited) is that kernel PPS provides better performance, and is
used for a very limited set of operations (possibly just timestamping the
PPS signal). All the filtering /is/ done in user-land. It isn't a pain
to do, once you have found the appropriate two or three command-lines for
your system.
Cheers,
David
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