netdev - Re: [PATCH 7/7] net: dsa: b53: Expose PTP timestamping ioctls to userspace

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Date:   Fri, 26 Nov 2021 09:42:32 +0100
From:   Kurt Kanzenbach <kurt@...utronix.de>
To:     Vladimir Oltean <olteanv@...il.com>,
        Richard Cochran <richardcochran@...il.com>
Cc:     Martin Kaistra <martin.kaistra@...utronix.de>,
        Florian Fainelli <f.fainelli@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        John Stultz <john.stultz@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Stephen Boyd <sboyd@...nel.org>,
        Russell King <linux@...linux.org.uk>,
        Marc Kleine-Budde <mkl@...gutronix.de>,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH 7/7] net: dsa: b53: Expose PTP timestamping ioctls to
 userspace

On Thu Nov 25 2021, Vladimir Oltean wrote:
> On Mon, Nov 08, 2021 at 06:48:24AM -0800, Richard Cochran wrote:
>> On Sun, Nov 07, 2021 at 04:27:03PM +0200, Vladimir Oltean wrote:
>> > On Sun, Nov 07, 2021 at 06:05:34AM -0800, Richard Cochran wrote:
>> > >         switch (cfg.rx_filter) {
>> > >         case HWTSTAMP_FILTER_NONE:
>> > >                 break;
>> > >         case HWTSTAMP_FILTER_ALL:
>> > >         case HWTSTAMP_FILTER_SOME:
>> > >         case HWTSTAMP_FILTER_PTP_V1_L4_EVENT:
>> > >         case HWTSTAMP_FILTER_PTP_V1_L4_SYNC:
>> > >         case HWTSTAMP_FILTER_PTP_V1_L4_DELAY_REQ:
>> > >         case HWTSTAMP_FILTER_NTP_ALL:
>> > >         case HWTSTAMP_FILTER_PTP_V2_L4_EVENT:
>> > >         case HWTSTAMP_FILTER_PTP_V2_L4_SYNC:
>> > >         case HWTSTAMP_FILTER_PTP_V2_L4_DELAY_REQ:
>> > >         case HWTSTAMP_FILTER_PTP_V2_L2_EVENT:
>> > >         case HWTSTAMP_FILTER_PTP_V2_L2_SYNC:
>> > >         case HWTSTAMP_FILTER_PTP_V2_L2_DELAY_REQ:
>> > >         case HWTSTAMP_FILTER_PTP_V2_EVENT:
>> > >         case HWTSTAMP_FILTER_PTP_V2_SYNC:
>> > >         case HWTSTAMP_FILTER_PTP_V2_DELAY_REQ:
>> > >                 cfg.rx_filter = HWTSTAMP_FILTER_PTP_V2_EVENT;
>> > >                 break;
>> > >         default:
>> > >                 mutex_unlock(&ocelot->ptp_lock);
>> > >                 return -ERANGE;
>> > >         }
>> > > 
>> > > That is essentially an upgrade to HWTSTAMP_FILTER_PTP_V2_EVENT.  The
>> > > change from ALL to HWTSTAMP_FILTER_PTP_V2_EVENT is probably a simple
>> > > oversight, and the driver can be easily fixed.
>> > > 
>> > > Thanks,
>> > > Richard
>> > 
>> > It's essentially the same pattern as what Martin is introducing for b53.
>> 
>> Uh, no it isn't.  The present patch has:
>> 
>> +       case HWTSTAMP_FILTER_PTP_V2_L2_EVENT:
>> +       case HWTSTAMP_FILTER_PTP_V2_L2_SYNC:
>> +       case HWTSTAMP_FILTER_PTP_V2_L2_DELAY_REQ:
>> +       case HWTSTAMP_FILTER_PTP_V2_EVENT:
>> +       case HWTSTAMP_FILTER_PTP_V2_SYNC:
>> +       case HWTSTAMP_FILTER_PTP_V2_DELAY_REQ:
>> +       case HWTSTAMP_FILTER_ALL:
>> +               config->rx_filter = HWTSTAMP_FILTER_PTP_V2_L2_EVENT;
>> 
>> There is an important difference between
>> HWTSTAMP_FILTER_PTP_V2_L2_EVENT and HWTSTAMP_FILTER_PTP_V2_EVENT
>> 
>> Notice the "L2" in there.
>
> Richard, when the request is PTP_V2_EVENT and the response is
> PTP_V2_L2_EVENT, is that an upgrade or a downgrade?

It is a downgrade, isn't it?

> PTP_V2_EVENT also includes PTP_V2_L4_EVENT.

Yes, exactly.

Thanks,
Kurt

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