netdev - Re: [RFC PATCH net-next] ptp: Introduce PTP_SYS_OFFSET_EXTENDED

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Message-ID: <613C833A-96C6-4B9C-AF45-AA81689CB644@amazon.com>
Date: Tue, 29 Jul 2025 02:29:26 +0000
From: "Ridoux, Julien" <ridouxj@...zon.com>
To: David Woodhouse <dwmw2@...radead.org>, "Arinzon, David"
	<darinzon@...zon.com>, David Miller <davem@...emloft.net>, Jakub Kicinski
	<kuba@...nel.org>, Richard Cochran <richardcochran@...il.com>, Eric Dumazet
	<edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>, "Woodhouse, David"
	<dwmw@...zon.co.uk>, Andrew Lunn <andrew@...n.ch>, Miroslav Lichvar
	<mlichvar@...hat.com>, Thomas Gleixner <tglx@...utronix.de>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
CC: "Machulsky, Zorik" <zorik@...zon.com>, "Matushevsky, Alexander"
	<matua@...zon.com>, "Bshara, Saeed" <saeedb@...zon.com>, "Wilson, Matt"
	<msw@...zon.com>, "Liguori, Anthony" <aliguori@...zon.com>, "Bshara, Nafea"
	<nafea@...zon.com>, "Schmeilin, Evgeny" <evgenys@...zon.com>, "Belgazal,
 Netanel" <netanel@...zon.com>, "Saidi, Ali" <alisaidi@...zon.com>,
	"Herrenschmidt, Benjamin" <benh@...zon.com>, "Kiyanovski, Arthur"
	<akiyano@...zon.com>, "Dagan, Noam" <ndagan@...zon.com>, "Bernstein, Amit"
	<amitbern@...zon.com>, "Ostrovsky, Evgeny" <evostrov@...zon.com>, "Tabachnik,
 Ofir" <ofirt@...zon.com>, "Levinson, Josh" <joshlev@...zon.com>
Subject: Re: [RFC PATCH net-next] ptp: Introduce
 PTP_SYS_OFFSET_EXTENDED_TRUSTED ioctl

> On 7/24/25, 7:09 AM, "David Woodhouse" <dwmw2@...radead.org <mailto:dwmw2@...radead.org>> wrote:
> 
> On Thu, 2025-07-24 at 14:56 +0300, David Arinzon wrote:
> > 
> > The proposed PTP_SYS_OFFSET_EXTENDED_TRUSTED ioctl fulfills both
> > objectives by extending each PHC timestamp with two quality
> > indicators:
> > 
> > - error_bound: a device-calculated value (in nanoseconds)
> > reflecting the maximum possible deviation of the timestamp from
> > the true time, based on internal clock state.
> > 
> > - clock_status: a qualitative state of the clock, with defined
> > values including:
> > 1. Unknown: the clock's synchronization status cannot be
> > reliably determined.
> > 2. Initializing: the clock is acquiring synchronization.
> > 3. Synchronized: The clock is actively being synchronized and
> > maintained accurately by the device.
> > 4. FreeRunning: the clock is drifting and not being
> > synchronized and updated by the device.
> > 5. Unreliable: the clock is known to be unreliable, the
> > error_bound value cannot be trusted.
> 
> 
> Should this also include a 'type' field matching vmclock & virtio-rtc?
> Especially if it's a smeared type, that is a (contra-)indication of the
> quality of the clock.

That is a good suggestion. Let's add it.

 
> Julien, I assume you're happy that this is *maxerror* and we completely
> ignore esterror which should never exist anyway?

Absolutely, and you are right, having *maxerror* only makes me happy :-)