[ntp:hackers] u-blox reference clock driver

[Trevor N.]

>Yo Achim!
>
>On Tue, 28 Aug 2018 19:28:32 +0200
>Achim Gratz via devel <devel at ntpsec.org> wrote:
>
>> Gary E. Miller via devel writes:
>> > We probably need to work with linuxpps, but we may have an easier
>> > time working with the folks that maintain the Raspberry Pi fork.
>> > The last time I asked for a dtb change it took one day to get in
>> > git head.  
>> 
>> The only thing that linuxpps would be the correct target for is
>> getting the PPS echo facility to do something useful with GPIO (and
>> maybe serial, but that's a whole 'nother driver to consider).
>
>Yes.  But until we have a kernel driver, the rest is pointless.
>
>> > Lukas told me, privately, he had already submitted it the the
>> > LKM folks and been overwhelmed by the changes they requested.  So
>> > the patch will clearly need work.  
>> 
>> That does not surprise me, given it's all a pretty ugly hack that
>> really only works for the one single thing he's needed it for.  I'm
>> not blaming him, just a reminder that getting things upstream takes a
>> lot more apple polishing.
>
>Agreed.  Lukas made a good start, but more to do.
>
>RGDS
>GARY

I added PPS output to the linuxpps parallel port module a while back.
I intend to use it to trigger the timemark input on the Trimble
Palisade/Acutime with more accuracy than can be done in user space
with the current driver. I ran out of free time, though, so I have
been unable to proceed.  I also added a polled mode to work around
interrupt latency, along with a low-latency echo output. It can be
found at
https://github.com/retroman/pps_parport_polled