linux-kernel - Re: [PATCH net-next v5] net: sfp: extend SMBus support

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Message-ID: <92538fd0-aa1f-429b-9984-89bcd46e2a28@lunn.ch>
Date: Thu, 22 Jan 2026 17:04:29 +0100
From: Andrew Lunn <andrew@...n.ch>
To: Jonas Jelonek <jelonek.jonas@...il.com>
Cc: Maxime Chevallier <maxime.chevallier@...tlin.com>,
	Russell King <linux@...linux.org.uk>,
	Heiner Kallweit <hkallweit1@...il.com>,
	"David S . Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	Bjørn Mork <bjorn@...k.no>
Subject: Re: [PATCH net-next v5] net: sfp: extend SMBus support

On Thu, Jan 22, 2026 at 11:14:03AM +0100, Jonas Jelonek wrote:
> Hi Andrew,
> 
> On 18.01.26 16:39, Andrew Lunn wrote:
> > On Sun, Jan 18, 2026 at 10:43:12AM +0100, Jonas Jelonek wrote:
> >> Hi,
> >>
> >> On 16.01.26 15:25, Andrew Lunn wrote:
> >>>> But let's first figure-out if word-only smbus are really a thing
> >>> Some grep foo on /drivers/i2c/busses might answer that.
> >> Did that and haven't found any driver in mainline which is word-only.
> >> All drivers with word access capability have byte access too.
> > So for the moment, maybe add a WARN_ON() for an I2C bus that only
> > supports word access, and we can deal with it only if we ever get a
> > report of it firing.
> 
> Should it just have a WARN_ON and continue (so it may work in some cases)
> or fail at that point? 

I guess doing a word access when a byte access is wanted will either
work, or immediately kill the I2C bus because the SFP is broken and
only supports byte access, and the dead I2C bus will cause a cascade
of errors.

So continue seems reasonable and hope for the best.

   Andrew