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

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Message-ID: <5074364c-31c6-4fa6-a705-f10ffd7cb16a@bootlin.com>
Date: Fri, 16 Jan 2026 14:14:46 +0100
From: Maxime Chevallier <maxime.chevallier@...tlin.com>
To: Jonas Jelonek <jelonek.jonas@...il.com>
Cc: 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>, Russell King <linux@...linux.org.uk>,
 Andrew Lunn <andrew@...n.ch>, Heiner Kallweit <hkallweit1@...il.com>
Subject: Re: [PATCH net-next v4] net: sfp: add SMBus I2C block support

Hi Jonas

On 16/01/2026 12:16, 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 :(

That's OK

> 
> 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

I don't think this patch is fit for upstream indeed. I remember Antoine
working on this back in the days, but don't know if he's even aware
that it made it into openwrt.

Nevertheless, let's keep everything in the mdio-i2c driver. I may give
this a shot at some point but I can't make any promise as to when :(

Maxime