linux-kernel - Re: [PATCH net-next v6 07/16] net_tstamp: Add TIMESTAMPING SOFTWARE and HARDWARE mask

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Date:   Tue, 24 Oct 2023 10:21:15 -0400
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     Köry Maincent <kory.maincent@...tlin.com>
Cc:     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>,
        Jakub Kicinski <kuba@...nel.org>,
        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>,
        Jonathan Corbet <corbet@....net>,
        Horatiu Vultur <horatiu.vultur@...rochip.com>,
        UNGLinuxDriver@...rochip.com, Simon Horman <horms@...nel.org>,
        Vladimir Oltean <vladimir.oltean@....com>,
        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>
Subject: Re: [PATCH net-next v6 07/16] net_tstamp: Add TIMESTAMPING SOFTWARE
 and HARDWARE mask

On Tue, Oct 24, 2023 at 9:40 AM Köry Maincent <kory.maincent@...tlin.com> wrote:
>
> On Thu, 19 Oct 2023 10:48:04 -0400
> Willem de Bruijn <willemdebruijn.kernel@...il.com> wrote:
>
> > On Thu, Oct 19, 2023 at 10:29 AM Kory Maincent
> > <kory.maincent@...tlin.com> wrote:
> > >
> > > Timestamping software or hardware flags are often used as a group,
> > > therefore adding these masks will easier future use.
> >
> > This assumes that device support for timestamping is often symmetric:
> > a device supports both rx and tx, or neither.
> >
> > All devices support software receive timestamping, as that timestamp
> > is taken in the core network stack. But to support transmit timestamps
> > drivers have to call sbk_tstamp_tx in their ndo_start_xmit.
>
> Yes, and in that software only case they often call ethtool_op_get_ts_info to
> fill the timestamp info.
>
> There is several drivers that support hardware and software timestamp, these
> mask could be useful for these. In case of asymmetric support we can still use
> the SOF_TIMESTAMPING_RX/TX_SOFTWARE flags.
>
> I forgot to specify, in the commit message but this patch is mainly to ease
> the next patch of this series to deal with software/hardware time stamping.
> Maybe you prefer to have this squash into next patch as had suggested Florian
> in last version.

Thanks. I did not see such use in net/ or in my experience of using
setsockopt SO_TIMESTAMPING.

But I had not considered net device get_ts_info. It would be useful there.

Slight preference from me to keep this a separate patch, as it applies
not only to the use case in your follow-on patch.