On Thu, 23 Sep 2010, Alan Cox wrote:

quoted

Please do not introduce useless additional layers for clock sync. Load
these ptp clocks like the other regular clock modules and make them sync
system time like any other clock.

I don't think you understand PTP. PTP has masters, a system can need to
be honouring multiple conflicting masters at once.

The upshot of it all has to be some synchronized notion of time regardless
of how many other things are going on under the hood. And the spec here
suggests a hardware able to generate periodic accurate events that can be
used to sync system time.

quoted

Really guys: I want a PTP solution! Now! And not some idiotic additional
kernel layers that just pass bits around because its so much fun and
screws up clock accurary in due to the latency noise introduced while
having so much fun with the bits.

There are some interesting complications in putting a PTP sync
interface in kernel.

If the PTP logic internally has to juggle multiple clocks then that is a
complication for the driver ok. In any case the driver ultimately has to
provide *one* source of time for the system to sync to.