Re: [Linuxptp-users] clock_nanosleep on /dev/ptpX (2022)

[Richard C. <ric...@gm...>]

On Sat, Oct 01, 2022 at 10:10:37AM -0700, todd freed wrote:
> I gather from the ENOTSUPP return that it's also not implemented
> today. I'm running linux 5.19.7. Just wanted confirmation on that
> point?

Correct.  Will not ever happen.  Big can of worms.

> I could run phc2sys on these hosts and then sleep against
> CLOCK_MONOTONIC. But I had wanted to avoid that, simply because some
> of the devices (desktop pcs) are being used for things other than this
> specific application, and I'd not like to takeover the systemwide
> clock.

If you really can't/won't use phc2sys, then you can also do

   clock_gettime(CLOCK_MONOTONIC, t1);
   clock_gettime(phc, t2);
   clock_gettime(CLOCK_MONOTONIC, t3);

and calculate

   offset = ((t3 - t1) / 2) - t2

every once in a while, then use linear interpolation to convert
deadlines from the PHC time scale into monotonic deadlines.

HTH,
Richard