linux-kernel - Re: [PATCH net-next v7 15/16] net: ethtool: ts: Let the active time stamping layer be selectable

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Message-ID: <20231124172754.tneftor7uobrul5f@skbuf>
Date:   Fri, 24 Nov 2023 19:27:54 +0200
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     Willem de Bruijn <willemb@...gle.com>
Cc:     Jakub Kicinski <kuba@...nel.org>,
        Köry Maincent <kory.maincent@...tlin.com>,
        Florian Fainelli <florian.fainelli@...adcom.com>,
        Broadcom internal kernel review list 
        <bcm-kernel-feedback-list@...adcom.com>,
        Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Richard Cochran <richardcochran@...il.com>,
        Radu Pirea <radu-nicolae.pirea@....nxp.com>,
        Jay Vosburgh <j.vosburgh@...il.com>,
        Andy Gospodarek <andy@...yhouse.net>,
        Nicolas Ferre <nicolas.ferre@...rochip.com>,
        Claudiu Beznea <claudiu.beznea@...on.dev>,
        Willem de Bruijn <willemdebruijn.kernel@...il.com>,
        Jonathan Corbet <corbet@....net>,
        Horatiu Vultur <horatiu.vultur@...rochip.com>,
        UNGLinuxDriver@...rochip.com, Simon Horman <horms@...nel.org>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org,
        Maxime Chevallier <maxime.chevallier@...tlin.com>,
        Mahesh Bandewar <maheshb@...gle.com>
Subject: Re: [PATCH net-next v7 15/16] net: ethtool: ts: Let the active time
 stamping layer be selectable

Hi Willem,

On Wed, Nov 22, 2023 at 01:11:02PM -0500, Willem de Bruijn wrote:
> There already is a disconnect between configuring hardware timestamp
> generation. Through the ioctl, which is a global admin-only interface.
> And requesting timestamps with SO_TIMESTAMPING.
> 
> Today the user of ptp4l already has to know that the admin has
> configured the right RX and TX filters. That is no different if
> multiple filters can be installed? (PHY for PTP, DMA for everything
> else).

Are you saying that ptp4l doesn't configure the RX and TX filters by
itself, just the admin had to do that? Because it does.
https://github.com/richardcochran/linuxptp/blob/master/sk.c#L59

I'm not seeing the disconnect. SO_TIMESTAMPING is for the socket,
SIOCSHWTSTAMP is for the configuration at the device level.

It _is_ different if multiple filters can be installed, because either
we let things be (and ptp4l issues the same ioctl which affects the
default hwtstamp provider, which may or may not coincide with what we
intend), or we teach ptp4l to deal with the multitude of providers that
a port may have.