netdev - Re: [PATCH net-next v4] net: sfp: add SMBus I2C block support

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Message-ID: <aWofM8Y0AIHVESml@shell.armlinux.org.uk>
Date: Fri, 16 Jan 2026 11:21:23 +0000
From: "Russell King (Oracle)" <linux@...linux.org.uk>
To: Jonas Jelonek <jelonek.jonas@...il.com>
Cc: Maxime Chevallier <maxime.chevallier@...tlin.com>,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	Bjørn Mork <bjorn@...k.no>,
	Paolo Abeni <pabeni@...hat.com>, Jakub Kicinski <kuba@...nel.org>,
	Eric Dumazet <edumazet@...gle.com>,
	"David S . Miller" <davem@...emloft.net>,
	Andrew Lunn <andrew@...n.ch>,
	Heiner Kallweit <hkallweit1@...il.com>
Subject: Re: [PATCH net-next v4] net: sfp: add SMBus I2C block support

On Fri, Jan 16, 2026 at 12:16:11PM +0100, Jonas Jelonek wrote:
> Hi Maxime,
> 
> On 09.01.26 18:03, Maxime Chevallier wrote:
> > ACK, I'll gladly help with testing. This should actually be easily
> > achievable with a board that has a real i2c interface connected to the
> > SFP cage, as there's a i2c smbus emulation layer. The SMBus helpers will
> > work with a true I2C adapter, you may have to tweak the code though.
> >
> > This is relevant for modules that have a built-in PHY that you can
> > access, if you don't have any I can run some tests here, I have more
> > than enough modules...
> >
> > If you don't have time at all for that, I may give this a shot at some
> > point, but my time is a bit scarce right now :'(
> >
> 
> I'd postpone this part if that's ok. Quite busy at the moment :(
> 
> When I come to trying to work on that, should that all be kept in
> mdio-i2c.c? I'm asking because we have a downstream implementation
> moving that SMbus stuff to mdio-smbus.c. This covers quite a lot right
> now, C22/C45 and Rollball, but just with byte access [1]. Because that
> isn't my work, I'll need to check with the original authors and adapt this
> for an upstream patch, trying to add word + block access.
> 
> Kind regards,
> Jonas
> 
> [1] https://github.com/openwrt/openwrt/blob/66b6791abe6f08dec2924b5d9e9e7dac93f37bc4/target/linux/realtek/patches-6.12/712-net-phy-add-an-MDIO-SMBus-library.patch

My personal view on this is not suitable for sharing publicly. I'm sure
people can guess what my view is and why. (Look at the age of the
patch, and it's clearly "lets re-implement mdio-i2c" rather than "let's
adapt it".

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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