netdev - Re: [PATCH net-next v6 4/7] net: dsa: hellcreek: Add support for hardware timestamping

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Message-ID: <87imbn98dd.fsf@kurt>
Date:   Tue, 06 Oct 2020 08:27:42 +0200
From:   Kurt Kanzenbach <kurt@...utronix.de>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
        Rob Herring <robh+dt@...nel.org>, devicetree@...r.kernel.org,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Richard Cochran <richardcochran@...il.com>,
        Kamil Alkhouri <kamil.alkhouri@...offenburg.de>,
        ilias.apalodimas@...aro.org
Subject: Re: [PATCH net-next v6 4/7] net: dsa: hellcreek: Add support for hardware timestamping

On Sun Oct 04 2020, Vladimir Oltean wrote:
> On Sun, Oct 04, 2020 at 01:29:08PM +0200, Kurt Kanzenbach wrote:
>> +/* Enabling/disabling TX and RX HW timestamping for different PTP messages is
>> + * not available in the switch. Thus, this function only serves as a check if
>> + * the user requested what is actually available or not
>> + */
>
> Correct me if I'm wrong, but to the user it makes zero difference
> whether the hardware takes timestamps or not.

Why not? I think it makes a difference to the user b/o the precision.

> What matters is whether the skb will be delivered to the stack with a
> hardware timestamp or not, so you should definitely accept a
> hwtstamp_config with TX and RX timestamping disabled.
>

Sorry, I cannot follow you here.

Thanks,
Kurt

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