What is timepps.h used for?

[Hal Murray]

> ... and if you are not using gpsd ?

If you have PPS hardware, there are 3 approaches.

You can use GPSD.  It will use the kernel PPS capture if the kernel supports 
it.  If not, it will try user mode timing.  I think that is only available on 
Linux.

You can use the PPS driver.  That requires timepps.h to build and a few 
kernel modules (or the equivalent option built into the kernel): pps_core and 
pps_ldisc

You can let the kernel do all the work.  That's flag3 on the PPS driver.  It 
works significantly better, but requires building your own kernel.  It needs 
the CONFIG_NTP_PPS option.  That needs not NoHZ and most distros ship kernels 
with NoHZ.

-- 
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