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Date: Wed, 22 Nov 2023 08:54:59 -0800
From: Jakub Kicinski <kuba@kernel.org>
To: Vladimir Oltean <vladimir.oltean@nxp.com>
Cc: =?UTF-8?B?S8O2cnk=?= Maincent <kory.maincent@bootlin.com>, Florian
 Fainelli <florian.fainelli@broadcom.com>, Broadcom internal kernel review
 list <bcm-kernel-feedback-list@broadcom.com>, Andrew Lunn <andrew@lunn.ch>,
 Heiner Kallweit <hkallweit1@gmail.com>, Russell King
 <linux@armlinux.org.uk>, "David S. Miller" <davem@davemloft.net>, Eric
 Dumazet <edumazet@google.com>, Paolo Abeni <pabeni@redhat.com>, Richard
 Cochran <richardcochran@gmail.com>, Radu Pirea
 <radu-nicolae.pirea@oss.nxp.com>, Jay Vosburgh <j.vosburgh@gmail.com>, Andy
 Gospodarek <andy@greyhouse.net>, Nicolas Ferre
 <nicolas.ferre@microchip.com>, Claudiu Beznea <claudiu.beznea@tuxon.dev>,
 Willem de Bruijn <willemdebruijn.kernel@gmail.com>, Jonathan Corbet
 <corbet@lwn.net>, Horatiu Vultur <horatiu.vultur@microchip.com>,
 UNGLinuxDriver@microchip.com, Simon Horman <horms@kernel.org>, Thomas
 Petazzoni <thomas.petazzoni@bootlin.com>, netdev@vger.kernel.org,
 linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, Maxime Chevallier
 <maxime.chevallier@bootlin.com>
Subject: Re: [PATCH net-next v7 15/16] net: ethtool: ts: Let the active time
 stamping layer be selectable
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On Wed, 22 Nov 2023 16:36:18 +0200 Vladimir Oltean wrote:
> @Jakub, for your long-term "MAC timestamps for PTP, DMA for everything else".
> How do you see this? I guess we need some sort of priority function in
> the UAPI between hwtstamp providers.
> 
> And even with that, I think the enums that we currently have for filters
> are not specific enough. The most we could expose is:
> 
>                       MAC provider                      DMA provider
> 
> hwtstamp_rx_filters   HWTSTAMP_FILTER_PTP_V2_EVENT      HWTSTAMP_FILTER_ALL
> tx_type               HWTSTAMP_TX_ON                    HWTSTAMP_TX_ON
> 
> but it isn't clear: for PTP, does the DMA provider give you an RX
> timestamp too?

If we phrase it as "precise / approximate" rather than "MAC / DMA" - it
seems fairly intuitive to give the best timestamp available for a given
packet, no?

> What about a TX timestamp?

I was thinking - socket flag to make packets for a given socket request
precise timestamps.