linux-kernel - Re: [PATCH net-next 0/2] net: phy: sfp: Add single-byte SMBus SFP access

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Message-ID: <87h64hsxsi.fsf@miraculix.mork.no>
Date: Tue, 25 Feb 2025 19:07:41 +0100
From: Bjørn Mork <bjorn@...k.no>
To: "Russell King (Oracle)" <linux@...linux.org.uk>
Cc: Maxime Chevallier <maxime.chevallier@...tlin.com>, davem@...emloft.net,
        Andrew Lunn <andrew@...n.ch>, Jakub Kicinski <kuba@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>,
        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>
Subject: Re: [PATCH net-next 0/2] net: phy: sfp: Add single-byte SMBus SFP
 access

"Russell King (Oracle)" <linux@...linux.org.uk> writes:

>> I believe you are reading more into the spec than what's actually there.
>
> So I'm making up the quote above from SFF-8472.  Okay, if that's where
> this discussion is going, I'm done here.

No, not at all.  That was not what I meant.  Please accept my apologies.
This came out wrong. You are absolutely correct about reading the 16bit
diagnostic registers you quoted. I would never doubt that. I have an
extreme respect for you and your knowledge of these standards and the
practical hardware implications.

It was the conclusion that this fact prevents SMBus hosts I wanted to
question.  I still don't see that.  Some SMBus hosts might be able do 2
byte reads.  And if they can't, then I believe they can safely ignore
these registers without being out of spec.  Like the proposed solution.

I'll shut up now, to avoid confusing the discussion of Maxime's patches
further.

Bjørn