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

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Message-ID: <20211106003606.qvfkitgyzoutznlw@skbuf>
Date:   Sat, 6 Nov 2021 02:36:06 +0200
From:   Vladimir Oltean <olteanv@...il.com>
To:     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>,
        Kurt Kanzenbach <kurt@...utronix.de>,
        "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 Fri, Nov 05, 2021 at 05:18:04PM -0700, Richard Cochran wrote:
> On Fri, Nov 05, 2021 at 04:28:33PM +0200, Vladimir Oltean wrote:
> > What is the expected convention exactly? There are other drivers that
> > downgrade the user application's request to what they support, and at
> > least ptp4l does not error out, it just prints a warning.
> 
> Drivers may upgrade, but they may not downgrade.
> 
> Which drivers downgrade?  We need to fix those buggy drivers.
> 
> Thanks,
> Richard

Just a quick example
https://elixir.bootlin.com/linux/v5.15/source/drivers/net/ethernet/mscc/ocelot.c#L1178
I haven't studied the whole tree, but I'm sure there are many more.