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: <20231124154343.sr3ajyueoshke6tn@skbuf>
Date:   Fri, 24 Nov 2023 17:43:43 +0200
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     Köry Maincent <kory.maincent@...tlin.com>,
        Jakub Kicinski <kuba@...nel.org>
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>,
        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>
Subject: Re: [PATCH net-next v7 15/16] net: ethtool: ts: Let the active time
 stamping layer be selectable

On Thu, Nov 23, 2023 at 09:32:05AM -0800, Jakub Kicinski wrote:
> On Thu, Nov 23, 2023 at 04:00:56PM +0100, Köry Maincent wrote:
> > So, do we have a consensus? Vlad, do you agree on putting all under ethtool?
> > 
> > ETHTOOL_GET_TS_INFO will be in charge of replacing the SIOCGHWSTAMP
> > implementation. Need to add ETHTOOL_A_TSINFO_PHC_INDEX
> > ETHTOOL_A_TSINFO_QUALIFIER to the request.
> > 
> > ETHTOOL_GET_TS_INFO will list all the hwtstamp provider (aka "{phc_index,
> > qualifier}") through the dumpit callback. I will add a filter to be able to
> > list only the hwtstamp provider of one netdev.
> > 
> > ETHTOOL_SET_TS_INFO will be in charge of replacing the SIOCSHWSTAMP
> > implementation.
> 
> If not we can do a vote/poll? Maybe others don't find the configuration
> of timestamping as confusing as me.

If you mean the ETHTOOL_MSG_TSINFO_GET netlink message (ETHTOOL_GET_TS_INFO
is an ioctl), you're saying that you want to move the entire contents of
SIOCGHWSTAMP there, by making the kernel call ndo_hwtstamp_get() in
addition to the existing __ethtool_get_ts_info()?

Yeah, I don't know, I don't have a real objection, I guess it's fine.

What will be a bit of an "?!" moment for users is when ethtool gains
support for the SIOCGHWSTAMP/SIOCSHWSTAMP netlink replacements, but not
for the original ioctls. So hwstamp_ctl will be able to change timestamping
configuration, but ethtool wouldn't - all on the same system. Unless
ethtool gains an ioctl fallback for a ioctl that was never down its alley.

But by all means, still hold a poll if you want to. I would vote for
ethtool netlink, not because it's great, just because I don't have a
better alternative to propose.