linux-kernel - Re: [PATCH v3 3/5] net: Let the active time stamping layer be selectable.

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Message-ID: <c0719411-4c8a-4af8-9cd1-f3386b8b8d15@lunn.ch>
Date:   Fri, 10 Mar 2023 16:32:15 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Willem de Bruijn <willemdebruijn.kernel@...il.com>
Cc:     Köry Maincent <kory.maincent@...tlin.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Heiner Kallweit <hkallweit1@...il.com>, netdev@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-omap@...r.kernel.org,
        Michael Walle <michael@...le.cc>,
        Maxime Chevallier <maxime.chevallier@...tlin.com>,
        Richard Cochran <richardcochran@...il.com>,
        thomas.petazzoni@...tlin.com, Russell King <linux@...linux.org.uk>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Jonathan Corbet <corbet@....net>,
        Jay Vosburgh <j.vosburgh@...il.com>,
        Veaceslav Falico <vfalico@...il.com>,
        Andy Gospodarek <andy@...yhouse.net>,
        Joakim Zhang <qiangqing.zhang@....com>,
        Vladimir Oltean <vladimir.oltean@....com>,
        Claudiu Manoil <claudiu.manoil@....com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        UNGLinuxDriver@...rochip.com, Minghao Chi <chi.minghao@....com.cn>,
        Jie Wang <wangjie125@...wei.com>,
        Oleksij Rempel <linux@...pel-privat.de>,
        Sean Anderson <sean.anderson@...o.com>,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        Wolfram Sang <wsa+renesas@...g-engineering.com>,
        Alexander Lobakin <alexandr.lobakin@...el.com>,
        Marco Bonelli <marco@...eim.net>
Subject: Re: [PATCH v3 3/5] net: Let the active time stamping layer be
 selectable.

On Fri, Mar 10, 2023 at 09:59:53AM -0500, Willem de Bruijn wrote:
> Köry Maincent wrote:
> > On Wed, 08 Mar 2023 10:28:51 -0500
> > Willem de Bruijn <willemdebruijn.kernel@...il.com> wrote:
> > 
> > > >  
> > > > +	enum timestamping_layer selected_timestamping_layer;
> > > > +  
> > > 
> > > can perhaps be a single bit rather than an enum
> > 
> > I need at least two bits to be able to list the PTPs available.
> > Look at the ethtool_list_ptp function of the second patch.
> 
> In the available bitmap, yes. Since there are only two options,
> in the selected case, a single bit would suffice.

It was a bit tongue in cheek, but in an earlier thread discussing this
problem, i listed how there could be up to 7 time stampers on the path
from the RJ45 to the network stack.

We got into this problem by assuming there could only ever be one time
stamper. Lets try to avoid potential problems of assuming there can
only every be two time stampers by assuming there can be N stampers.

     Andrew