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

[todd f. <tod...@gm...>]

Okay, Richard, thanks for the confirmation and the suggestion.

Could you say just a bit more about why it shouldn't be implemented?
I'm a professional software engineer, and I had thought I might take a
look at implementing it myself. But if you wouldn't recommend such a
thing, I will avoid spending any time on it.

-Todd

On Sat, Oct 1, 2022 at 7:13 PM Richard Cochran <ric...@gm...> wrote:
>
> 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