linux-kernel - Re: [PATCH 7/7] net: dsa: b53: Expose PTP timestamping ioctls to userspace

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Message-ID: <20211126163108.GA27081@hoboy.vegasvil.org>
Date:   Fri, 26 Nov 2021 08:31:08 -0800
From:   Richard Cochran <richardcochran@...il.com>
To:     Kurt Kanzenbach <kurt@...utronix.de>
Cc:     Vladimir Oltean <olteanv@...il.com>,
        Martin Kaistra <martin.kaistra@...utronix.de>,
        Florian Fainelli <f.fainelli@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        John Stultz <john.stultz@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Stephen Boyd <sboyd@...nel.org>,
        Russell King <linux@...linux.org.uk>,
        Marc Kleine-Budde <mkl@...gutronix.de>,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH 7/7] net: dsa: b53: Expose PTP timestamping ioctls to
 userspace

On Fri, Nov 26, 2021 at 09:42:32AM +0100, Kurt Kanzenbach wrote:
> On Thu Nov 25 2021, Vladimir Oltean wrote:
> > Richard, when the request is PTP_V2_EVENT and the response is
> > PTP_V2_L2_EVENT, is that an upgrade or a downgrade?
> 
> It is a downgrade, isn't it?

Yes.  "Any kind of PTP Event" is a superset of "Any Layer-2 Event".

When userland asks for "any kind", then it wants to run PTP over IPv4,
IPv6, or Layer2, maybe even more than one at the same time.  If the
driver changes that to Layer2 only, then the PTP possibilities have
been downgraded.

Thanks,
Richard