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

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Message-ID: <6987689b-35ac-4c15-addb-1c8e54144fa7@gmail.com>
Date: Fri, 16 Jan 2026 14:43:47 +0100
From: Jonas Jelonek <jelonek.jonas@...il.com>
To: Maxime Chevallier <maxime.chevallier@...tlin.com>,
 Russell King <linux@...linux.org.uk>, Andrew Lunn <andrew@...n.ch>,
 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>
Cc: 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

Hi,

On 16.01.26 14:23, Maxime Chevallier wrote:
> I think Russell pointed it out, but I was also wondering the same.
> How do we deal with controllers that cannot do neither block nor
> single-byte, i.e. that can only do word access ?
>
> We can't do transfers that have an odd length. And there are some,
> see sfp_cotsworks_fixup_check() for example.
>
> Maybe these smbus controller don't even exist, but I think we should
> anyway have some log saying that this doesn't work, either at SFP
> access time, or at init time.

I tried to guard that in the sfp_i2c_configure() right now. The whole path
to allow SMBus transfers is only allowed if there's at least byte access. For
exactly the reason that we need byte access in case of odd lengths. Then,
it can upgrade to word or block access if available. Or did I miss anything in
the conditions?

This of course rules out any controllers which just can do word access.
I guess covering this case increases the complexity. But I'd be fine having a
log or something similar handling this condition.

Kind regards,
Jonas