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

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Date:   Mon, 24 Jan 2022 07:37:16 -0800
From:   Richard Cochran <richardcochran@...il.com>
To:     Miroslav Lichvar <mlichvar@...hat.com>
Cc:     Vladimir Oltean <vladimir.oltean@....com>,
        Andrew Lunn <andrew@...n.ch>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        David Miller <davem@...emloft.net>,
        Grygorii Strashko <grygorii.strashko@...com>,
        Jakub Kicinski <kuba@...nel.org>,
        Joakim Zhang <qiangqing.zhang@....com>,
        Kurt Kanzenbach <kurt@...utronix.de>,
        Russell King <linux@....linux.org.uk>
Subject: Re: [PATCH RFC V1 net-next 3/4] net: Let the active time stamping
 layer be selectable.

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