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: <20231122144453.5eb0382f@kmaincent-XPS-13-7390>
Date:   Wed, 22 Nov 2023 14:44:53 +0100
From:   Köry Maincent <kory.maincent@...tlin.com>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     Vladimir Oltean <vladimir.oltean@....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>
Subject: Re: [PATCH net-next v7 15/16] net: ethtool: ts: Let the active time
 stamping layer be selectable

On Tue, 21 Nov 2023 09:43:54 -0800
Jakub Kicinski <kuba@...nel.org> wrote:

> On Tue, 21 Nov 2023 18:31:14 +0100 Köry Maincent wrote:
> > - Expand struct hwtstamp_config with a phc_index member for the
> > SIOCG/SHWTSTAMP commands.
> >   To keep backward compatibility if phc_index is not set in the
> > hwtstamp_config data from userspace use the default hwtstamp (the default
> > being selected as done in my patch series).
> >   Is this possible, would it breaks things?  
> 
> I'd skip this bit, and focus on the ETHTOOL_TSINFO. Keep the ioctl as
> "legacy" and do all the extensions in ethtool. TSINFO_GET can serve
> as GET, to avoid adding 3rd command for the same thing. TSINFO_SET
> would be new (as you indicate below).

You say this patch series should simply add TSINFO_SET command to set the
current phc_index?

It won't solve your requirement of having simultaneous hwtimestamp and
enabling/disabling them through rx_filter and tx_types.
You want to do this in another patch series alongside a new SIOCG/SHWTSTAMP_2
ABI?

> > - In netlink part, send one netlink tsinfo skb for each phc_index.  
> 
> phc_index and netdev combination. A DO command can only generate one
> answer (or rather, it should generate only one answer, there are few
> hard rules in netlink). So we need to move that functionality to DUMP.
> We can filter the DUMP based on user-provided ifindex and/or phc_index.

Currently, the dumpit function is assigned to ethnl_default_dumpit. Wouldn't
the behavior change of the dumpit callback break the ABI?


> > Could be done in a later patch series:
> > - Expand netlink TSINFO with ETHTOOL_A_TSINFO_HWSTAMP_PROVIDER_QUALIFIER.
> >   Describing this struct:
> > enum ethtool_hwstamp_provider_qualifier {
> >  	ETHTOOL_HWSTAMP_PROVIDER_QUALIFIER_PRECISE,
> >  	ETHTOOL_HWSTAMP_PROVIDER_QUALIFIER_APPROX,
> > }; 
> > 
> >   Set the desired qualifier through TSINFO_SET or through SIOCSHWTSTAMP by
> >   expanding again the struct hwtstamp_config.

Just wondering to have a insight of future support, in the case of several
provider qualifier and the SIOCG/SHWTSTAMP_2 layout containing the phc_index.
Will we be able to talk to the two providers qualifiers simultaneously or is it
not possible. To know if the SIOCG/SHWTSTAMP_2 layout would contain the
description of the qualifier provider.
If I understand well your mail in the thread it will be the case right?

Regards,
-- 
Köry Maincent, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com