netdev - Re: [PATCH 0/2] [RFC] posix clock tuning

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Message-ID: <20100905062240.GB2699@riccoc20.at.omicron.at>
Date:	Sun, 5 Sep 2010 08:22:40 +0200
From:	Richard Cochran <richardcochran@...il.com>
To:	Christoph Lameter <cl@...ux.com>
Cc:	Christian Riesch <christian.riesch@...il.com>,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-api@...r.kernel.org
Subject: Re: [PATCH 0/2] [RFC] posix clock tuning

On Sat, Sep 04, 2010 at 08:47:39PM -0500, Christoph Lameter wrote:
> On Sat, 4 Sep 2010, Christian Riesch wrote:
> 
> > Richard's idea is to support clock hardware for IEEE 1588 (PTP, Precision Time
> > Protocol). Have a look at the earlier discussions:
> >
> > http://lkml.org/lkml/2010/8/16/90
> 
> A superficial scan does not give me any definite agreement on an approach.

Welcome to the club. I am also not too sure how to bring everything
that was said together.

I have attempted to synthesize the various ideas from the previous
threads into a concrete form (a new patch set) in order to see:

1. If I understood what the commentators were asking for.
2. Whether people now agree on the approach.

> Ok this goes more into something that may prove useful but it would be
> very helpful still to have a clear discussion as to why this is all
> needed. From what I can tell the functionality is already there and
> another clock device (CLOCK_SGI_CYCLE) is already providing a model for
> how a PTP clock could be controlled and used.

John Stultz warned against that approach in his mail from August 18.

    http://lkml.org/lkml/2010/8/18/264

At this point, I think it is clear that, in order to support IEEE
1588, some kind of changes are needed. I have argued and discussed the
issues at some length. I am willing to continue the discussion, but I
would also appreciate more than a "superficial scan." PTP is quite a
large topic that probably cannot be adequately treated in a single
email.

Having said that, if you are convinced that the existing interfaces
are good enough to support PTP (and possible future methods, as
discussed in the threads), then I am all ears to find out how to do
make it work.

Thanks,
Richard

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