Re: [PATCH RFC V1 net-next 3/4] net: Let the active time stamping layer be selectable.

From: Richard Cochran <richardcochran@gmail.com>
To: Miroslav Lichvar <mlichvar@redhat.com>
Cc: Vladimir Oltean <vladimir.oltean@nxp.com>,
	Andrew Lunn <andrew@lunn.ch>,
	"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	David Miller <davem@davemloft.net>,
	Grygorii Strashko <grygorii.strashko@ti.com>,
	Jakub Kicinski <kuba@kernel.org>,
	Joakim Zhang <qiangqing.zhang@nxp.com>,
	Kurt Kanzenbach <kurt@linutronix.de>,
	Russell King <linux@arm.linux.org.uk>
Subject: Re: [PATCH RFC V1 net-next 3/4] net: Let the active time stamping layer be selectable.
Date: Mon, 24 Jan 2022 07:37:16 -0800	[thread overview]
Message-ID: <20220124153716.GB28194@hoboy.vegasvil.org> (raw)
In-Reply-To: <Ye5xN6sQvsfX1lmn@localhost>

On Mon, Jan 24, 2022 at 10:28:23AM +0100, Miroslav Lichvar wrote:

> FWIW, scm_timestamping has three fields and the middle one no longer
> seems to be used. If a new socket/timestamping option enabled all
> three (SW, MAC, PHY) timestamps in the cmsg, I think that would be a
> nice feature.

This won't work because:

- There would need to be seven^W eight, not three slots.

- Even with just three, the CMSG would have to have a bit that clearly
  identifies the new format.

> From an admin point of view, it makes sense to me to have an option to
> disable PHY timestamps for the whole device if there are issues with
> it. For debugging and applications, it would be nice to have an option
> to get all of them at the same time.

Right.  Those are two different use cases.  The present series
addresses the first one.  The second one entails making a new flavor
of time stamping API.

Thanks,
Richard