linux-kernel - Re: [PATCH net-next v1 2/4] net: phy: micrel: lan8841: set default PTP latency values

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Date: Tue, 23 Apr 2024 09:07:59 +0200
From: Oleksij Rempel <o.rempel@...gutronix.de>
To: Richard Cochran <richardcochran@...il.com>
Cc: Andrew Lunn <andrew@...n.ch>,
	Alexandre Torgue <alexandre.torgue@...s.st.com>,
	Jose Abreu <joabreu@...opsys.com>,
	"David S. Miller" <davem@...emloft.net>,
	Heiner Kallweit <hkallweit1@...il.com>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Maxime Coquelin <mcoquelin.stm32@...il.com>,
	Woojung Huh <woojung.huh@...rochip.com>,
	Arun Ramadoss <arun.ramadoss@...rochip.com>,
	Russell King <linux@...linux.org.uk>, kernel@...gutronix.de,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	UNGLinuxDriver@...rochip.com,
	linux-stm32@...md-mailman.stormreply.com
Subject: Re: [PATCH net-next v1 2/4] net: phy: micrel: lan8841: set default
 PTP latency values

Hi Richard,

On Thu, Apr 18, 2024 at 11:46:48PM -0700, Richard Cochran wrote:
> On Wed, Apr 17, 2024 at 10:23:07PM +0200, Andrew Lunn wrote:
> > I suggest you go read older messages from Richard. It was a discussion
> > with Microchip about one of their PHYs.
> 
> My 2 cents:
> 
> User space has all of the hooks needed to configure corrections for a
> given setup.
> 
> Hard coding corrections in device drivers is bound to fail, based on
> prior experience with Vendors not knowing or caring how their products
> actually work.  Vendors will publish value X one year, then delete the
> info (to avoid embarrassment), then publish the new value Y, once
> customers have forgotten about X.
> 
> So, prudent users will always calibrate their beloved systems, not
> trusting the Vendors to provide anything close to reasonable.
> 
> Ergo, adding new magical correction in a kernel release causes
> regressions for prudent users.
> 
> But, in the end, that doesn't matter, because prudent users are used
> to being abused by well-meaning yet misguided device driver authors.
> 
> Prudent users are wise, and they will re-calibrate their systems
> before rolling out an updated kernel.

Ok, i see. Thank you for your feedback.

Are the recommended FOSS projects managing calibration values per-
linkmode/port/device in user space?

What is recommended way for calibration? Using some recommended device?

Regards,
Oleksij
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