From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from pandora.armlinux.org.uk (pandora.armlinux.org.uk [78.32.30.218]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7E2952DBF45; Sun, 18 Jan 2026 10:08:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=78.32.30.218 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768730908; cv=none; b=HqJKbWeSh+FZUPrRoVf8FUZ6U3V07pRkyUn+8zJw7hDJvGK7L+aBqgLmbruHP2LRLuRbaBBs6vQOtYldhorrUGcLMkwUE7pJDONWUAGVwhHhs2CkDoyDpS9cVpb0vmImAEriPN3Q09peImPFsGc3U93NlW0PymdK9pSQ/xeYkBU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768730908; c=relaxed/simple; bh=zfG9kR6GVytGzJo0EGQoTa6uMlq3njmHNwkLqAF/SGg=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=g8w1ZlYC3qJCxqL6AhkbO2pQmlb2peQLEIkZEYhnw2IzFNzg6CH2WU3ARAXH7vdHMPV9Ao3HyYw6+eEWSxHBEyETm/5WYRA60HDjrJIV1boUn4Df9HeRNQRwN59bY6yvGi2VMbj3dlXFZLZu3WYUAZIz1Qhvy7j5FSYywuhd7/o= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=armlinux.org.uk; spf=none smtp.mailfrom=armlinux.org.uk; dkim=pass (2048-bit key) header.d=armlinux.org.uk header.i=@armlinux.org.uk header.b=afZ6jmAo; arc=none smtp.client-ip=78.32.30.218 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=armlinux.org.uk Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=armlinux.org.uk Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=armlinux.org.uk header.i=@armlinux.org.uk header.b="afZ6jmAo" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=armlinux.org.uk; s=pandora-2019; h=Sender:In-Reply-To: Content-Transfer-Encoding:Content-Type:MIME-Version:References:Message-ID: Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=gykQHQfAXfGx+5mcrgwAVp3gTYmzOFfNes+NNjpoUjk=; b=afZ6jmAobpwl3nv90bjh5cQDLP rT0PLqvLQt3p1ixKGks/TSBYIMQ3lM9Sey+nzKRhsd4/Z2rqnxqnGn6+1EzyXX6u6A6s0hlwu1hFE EMofF3I4mdKYyR7bCgZe2gtE3oTpTrm9fOI4ymXGqqVoESebCFbHX8Y6UKw2lFbhohvR5GpV0X084 aBcyZDSLyn+k2Ayn+9NwXGiDD9AK1VAhp4BWdHOA3oJbcz/KJNjQyAzDtXDm73+FdP6TQ/GnilhMm B398TAji6ZO5NKlKroUtGoyVl9yL+mEOxbPvAS27bXg9N/TrYj0zfqHWjPPn+ZeFRx0BSLkN2M8yq zPduy8Iw==; Received: from shell.armlinux.org.uk ([fd8f:7570:feb6:1:5054:ff:fe00:4ec]:41614) by pandora.armlinux.org.uk with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.98.2) (envelope-from ) id 1vhPhf-0000000047p-3qWx; Sun, 18 Jan 2026 10:08:15 +0000 Received: from linux by shell.armlinux.org.uk with local (Exim 4.98.2) (envelope-from ) id 1vhPhc-000000005Vf-2krW; Sun, 18 Jan 2026 10:08:12 +0000 Date: Sun, 18 Jan 2026 10:08:12 +0000 From: "Russell King (Oracle)" To: Jonas Jelonek Cc: Andrew Lunn , Maxime Chevallier , Heiner Kallweit , "David S . Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, =?iso-8859-1?Q?Bj=F8rn?= Mork Subject: Re: [PATCH net-next v5] net: sfp: extend SMBus support Message-ID: References: <20260116113105.244592-1-jelonek.jonas@gmail.com> <6a87648c-a1e8-49a2-a201-91108669ab44@bootlin.com> <6987689b-35ac-4c15-addb-1c8e54144fa7@gmail.com> <5e7c71f6-80dd-408b-a346-888e6febf07a@lunn.ch> <91442f3f-0da9-4c52-89ce-2ca0a3188836@gmail.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <91442f3f-0da9-4c52-89ce-2ca0a3188836@gmail.com> Sender: Russell King (Oracle) On Sun, Jan 18, 2026 at 10:43:12AM +0100, Jonas Jelonek wrote: > Looking at the SFP MSA [1], some sentences sound like one could assume > byte access is needed at least for SFP. In Section B4, there are statements > like: > - "The memories are organized as a series of 8-bit data words that can be >     addressed individually..." > - "...provides sequential or random access to 8 bit parameters..." > - "The protocol ... sequentially transmits one or more 8-bit bytes..." > > But that may be too vague and I can't judge if that's a valid argument to not > care about word-only here. There's a whole bunch of documents. You also need to look at SFF-8472. This contains the following paragraph: To guarantee coherency of the diagnostic monitoring data, the host is required to retrieve any multi-byte fields from the diagnostic monitoring data structure (e.g. Rx Power MSB - byte 104 in A2h, Rx Power LSB - byte 105 in A2h) by the use of a single two-byte read sequence across the 2-wire interface. Hence why we don't allow hwmon when only byte accesses are available. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!