The latency in the timer interrupt with Linux shouldn't be any more a
problem than with other systems. In any case, the PLL is not driven
directly by that signal. The important thing is that the timex.h structure
be compatible with the strucure used by the daemon; in particular, the
PPS variables. I suspect the kernel PPS mods are implmented, but with
no routine to call hardpps() at DCD transition. In which case just use
the structure defined in the kernel.tar distribution and get on with life.
The code will be a stub until somebody notches the serial driver to
snatch an interrupt when the DCD line wiggles. This is in fact exactly
the case now with Digital Unix 4.0 for the Alpha.
Dave