Re: [Linuxptp-users] Software clock

[Yan Yankovskyi via Linuxptp-users]

I need to use PTP synchronization for synchronizing video stream (something
like this). To do it I have to adjust the clock, but using the system clock
looks like bad architecture decision. So I decided to ask is it possible to
have some separate clock, that will be dedicated only for this purpose.
By the way, 802.1AS-2011 standard describes application interfaces (chapter
9), especially ClockTarget. Is it implemented in ptp4l, or it should be
implemented using some custom software?

On Thu, Mar 22, 2018 at 6:12 PM, Richard Cochran 
wrote:

>
> On Thu, Mar 22, 2018 at 09:15:31AM +0200, Yan Yankovskyi via
> Linuxptp-users wrote:
> > In case of use software timestamping we are adjusting system clock. Is it
> > possible to create another clock, and use it in ptp4l? I see that in
> > clock_create function in case if phc_index < 0 we use CLOCK_REALTIME as
> > value for clkid, so I suppose it isn't possible.
>
> Right.  The kernel delivers SW time stamps on CLOCK_REALTIME, and so
> the use of CLOCK_REALTIME with SW time stamping is hard coded.
>
> > But it implies that using
> > software timestamping we are limited to only one instance of ptp4l at the
> > same time, while using hardware timestamping we can launch as many ptp4l
> > instances simultaneously, as many physical devices we have, right?
>
> Well, using option free_running=1 you can have as many instances as
> you like, but I'm not sure why would anyone want to do this.  You can
> even launch multiple ptp4l programs on the same interface in different
> PTP domains, assuming at most one instance has free_running=0.
>
> What problem are you trying to solve?
>
> Thanks,
> Richard
>
>


-- 
Best regards,

Yan Yankovskyi | Junior Software Engineer, Ukraine
GlobalLogic
M  +380.95.049.64.73 <+380950496473>   Skype huandesale

www.globallogic.com

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Re: [Linuxptp-users] Software clock

[Richard Cochran]

On Thu, Mar 22, 2018 at 09:15:31AM +0200, Yan Yankovskyi via Linuxptp-users 
wrote:
> In case of use software timestamping we are adjusting system clock. Is it
> possible to create another clock, and use it in ptp4l? I see that in
> clock_create function in case if phc_index < 0 we use CLOCK_REALTIME as
> value for clkid, so I suppose it isn't possible.

Right.  The kernel delivers SW time stamps on CLOCK_REALTIME, and so
the use of CLOCK_REALTIME with SW time stamping is hard coded.

> But it implies that using
> software timestamping we are limited to only one instance of ptp4l at the
> same time, while using hardware timestamping we can launch as many ptp4l
> instances simultaneously, as many physical devices we have, right?

Well, using option free_running=1 you can have as many instances as
you like, but I'm not sure why would anyone want to do this.  You can
even launch multiple ptp4l programs on the same interface in different
PTP domains, assuming at most one instance has free_running=0.

What problem are you trying to solve?

Thanks,
Richard


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[Linuxptp-users] Software clock

[Yan Yankovskyi via Linuxptp-users]

Hello,
In case of use software timestamping we are adjusting system clock. Is it
possible to create another clock, and use it in ptp4l? I see that in
clock_create function in case if phc_index < 0 we use CLOCK_REALTIME as
value for clkid, so I suppose it isn't possible. But it implies that using
software timestamping we are limited to only one instance of ptp4l at the
same time, while using hardware timestamping we can launch as many ptp4l
instances simultaneously, as many physical devices we have, right?

-- 
Best regards,

Yan Yankovskyi | Junior Software Engineer, Ukraine
GlobalLogic
M  +380.95.049.64.73 <+380950496473>   Skype huandesale

www.globallogic.com

http://www.globallogic.com/email_disclaimer.txt
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