From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755315AbbCSNaU (ORCPT ); Thu, 19 Mar 2015 09:30:20 -0400 Received: from bh-25.webhostbox.net ([208.91.199.152]:48966 "EHLO bh-25.webhostbox.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752053AbbCSNaQ (ORCPT ); Thu, 19 Mar 2015 09:30:16 -0400 Message-ID: <550ACF66.5070208@roeck-us.net> Date: Thu, 19 Mar 2015 06:30:14 -0700 From: Guenter Roeck User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.5.0 MIME-Version: 1.0 To: Wolfram Sang CC: linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] eeprom: at24: Add support for large EEPROMs connected to SMBus adapters References: <20150204190819.GA15467@roeck-us.net> <20150204233516.GA1677@katana> <20150205002630.GA396@roeck-us.net> <20150205144028.GA4865@katana> <20150205175326.GA26691@roeck-us.net> <20150212040126.GA1691@roeck-us.net> <20150216120951.GA2840@katana> <20150317042049.GA6765@roeck-us.net> <20150318132707.GD3580@katana> <550A4162.8000009@roeck-us.net> <20150319081612.GA900@katana> In-Reply-To: <20150319081612.GA900@katana> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-Authenticated_sender: linux@roeck-us.net X-OutGoing-Spam-Status: No, score=-1.0 X-CTCH-PVer: 0000001 X-CTCH-Spam: Unknown X-CTCH-VOD: Unknown X-CTCH-Flags: 0 X-CTCH-RefID: str=0001.0A020206.550ACF67.0280,ss=1,re=0.001,recu=0.000,reip=0.000,cl=1,cld=1,fgs=0 X-CTCH-Score: 0.001 X-CTCH-ScoreCust: 0.000 X-CTCH-Rules: C_4847, X-CTCH-SenderID: linux@roeck-us.net X-CTCH-SenderID-Flags: 0 X-CTCH-SenderID-TotalMessages: 1 X-CTCH-SenderID-TotalSpam: 0 X-CTCH-SenderID-TotalSuspected: 0 X-CTCH-SenderID-TotalConfirmed: 0 X-CTCH-SenderID-TotalBulk: 0 X-CTCH-SenderID-TotalVirus: 0 X-CTCH-SenderID-TotalRecipients: 0 X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - bh-25.webhostbox.net X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - roeck-us.net X-Get-Message-Sender-Via: bh-25.webhostbox.net: mailgid no entry from get_relayhosts_entry X-Source: X-Source-Args: X-Source-Dir: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/19/2015 01:16 AM, Wolfram Sang wrote: > >> I don't call that multi-master, though, so I guess we may have a bit of a >> terminology problem. > > This is definately not a multi-master issue, I agree. It is just > another issue I saw when thinking about your patch thoroughly again. > >> I'll see what I can come up with, but I am not sure if I'll find the time >> before the 4.1 commit window opens. Company has a working solution (kind of), >> so now I'll have to do this on my own time ;-). > > But their solution is buggy and needs a fix! :) > I ended up looking into this last night, and actually have some untested code. However, looking through the kernel, the problem it solves turns out to be wide-spread. Almost every caller of i2c_smbus_read_byte() does the call as part of a call sequence, and thus has that very same problem. That includes, for example, the max1363 and the ds2482 drivers, both of which are used in our system. So, while the solution may be buggy, that bug is wide-spread and no one really seems to care about it (or did not realize it). This gives "needs a fix" a completely different scope. Given that, I may spend some time trying to see if I can reproduce the problem before trying to fix it. Thanks, Guenter