linux-kernel - Re: [PATCH net-next v4 1/2] net: phy: sfp: Add support for SMBus module access

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Message-ID: <24cff763-8312-4502-9e86-b20883ad616b@lunn.ch>
Date: Sat, 22 Mar 2025 16:28:55 +0100
From: Andrew Lunn <andrew@...n.ch>
To: Maxime Chevallier <maxime.chevallier@...tlin.com>
Cc: davem@...emloft.net, Jakub Kicinski <kuba@...nel.org>,
	Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>,
	Russell King <linux@...linux.org.uk>,
	Heiner Kallweit <hkallweit1@...il.com>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, thomas.petazzoni@...tlin.com,
	Florian Fainelli <f.fainelli@...il.com>,
	Köry Maincent <kory.maincent@...tlin.com>,
	Simon Horman <horms@...nel.org>,
	Romain Gantois <romain.gantois@...tlin.com>,
	Antoine Tenart <atenart@...nel.org>,
	Marek Behún <kabel@...nel.org>,
	Sean Anderson <sean.anderson@...ux.dev>,
	Bjørn Mork <bjorn@...k.no>
Subject: Re: [PATCH net-next v4 1/2] net: phy: sfp: Add support for SMBus
 module access

On Sat, Mar 22, 2025 at 08:57:44AM +0100, Maxime Chevallier wrote:
> The SFP module's eeprom and internals are accessible through an i2c bus.
> 
> It is possible that the SFP might be connected to an SMBus-only
> controller, such as the one found in some PHY devices in the VSC85xx
> family.
> 
> Introduce a set of sfp read/write ops that are going to be used if the
> i2c bus is only capable of doing smbus byte accesses.
> 
> As Single-byte SMBus transaction go against SFF-8472 and breaks the
> atomicity for diagnostics data access, hwmon is disabled in the case
> of SMBus access.
> 
> Moreover, as this may cause other instabilities, print a warning at
> probe time to indicate that the setup may be unreliable because of the
> hardware design.
> 
> As hwmon may be disabled for both broken EEPROM and smbus, the warnings
> are udpated accordingly.
> 
> Signed-off-by: Maxime Chevallier <maxime.chevallier@...tlin.com>

Reviewed-by: Andrew Lunn <andrew@...n.ch>

    Andrew