The Symmetricom PCI clock that I've been working on has the ability to
generate a PPS PCI interrupt based on it's on-board oscillator (or the
GPS module, if one is installed).

I added a simple ioctl to enable/disable the PPS interrupt and when enabled
it just calls hardpps().  But, I did not provide the PPSAPI interface.

So, while the kernel can benefit, ntpd does not (afaict).  So, the question
is whether I should add it?  Am I sacrificing accuracy by not making it
available to ntpd?