linux-kernel - Re: [PATCH net-next v5 08/16] net: ethtool: Add a command to expose current time stamping layer

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Message-ID: <6ef6418d-6e63-49bd-bcc1-cdc6eb0da2d5@lunn.ch>
Date:   Fri, 13 Oct 2023 18:11:19 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     Köry Maincent <kory.maincent@...tlin.com>,
        Florian Fainelli <florian.fainelli@...adcom.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        "David S . Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Jonathan Corbet <corbet@....net>,
        Jay Vosburgh <j.vosburgh@...il.com>,
        Andy Gospodarek <andy@...yhouse.net>,
        Nicolas Ferre <nicolas.ferre@...rochip.com>,
        Claudiu Beznea <claudiu.beznea@...on.dev>,
        Horatiu Vultur <horatiu.vultur@...rochip.com>,
        UNGLinuxDriver@...rochip.com,
        Broadcom internal kernel review list 
        <bcm-kernel-feedback-list@...adcom.com>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        Richard Cochran <richardcochran@...il.com>,
        Radu Pirea <radu-nicolae.pirea@....nxp.com>,
        Willem de Bruijn <willemdebruijn.kernel@...il.com>,
        Vladimir Oltean <vladimir.oltean@....com>,
        Michael Walle <michael@...le.cc>,
        Jacob Keller <jacob.e.keller@...el.com>,
        Maxime Chevallier <maxime.chevallier@...tlin.com>
Subject: Re: [PATCH net-next v5 08/16] net: ethtool: Add a command to expose
 current time stamping layer

> > All these possibles timestamps go through exclusively the netdev API or the
> > phylib API. Even the software timestamping is done in the netdev driver,
> > therefore it goes through the netdev API and then should have the
> > NETDEV_TIMESTAMPING bit set.
> 
> Netdev vs phylib is an implementation detail of Linux.
> I'm also surprised that you changed this.
> 
> > > > + */
> > > > +enum {
> > > > +	NO_TIMESTAMPING = 0,
> > > > +	NETDEV_TIMESTAMPING = (1 << 0),
> > > > +	PHYLIB_TIMESTAMPING = (1 << 1),
> > > > +	SOFTWARE_TIMESTAMPING = (1 << 2) | (1 << 0),    

Just emphasising Jakubs point here. phylib is an implementation
detail, in that the MAC driver might be using firmware to drive its
PHY, and that firmware can do a timestamp in the PHY. The API being
defined here should be independent of the implementation details. So
it probably should be MAC_TIMESTAMPING and PHY_TIMESTAMPING, and leave
it to the driver to decide if its PHYLIB doing the actual work, or
firmware.

	Andrew