From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752903AbbAVRSu (ORCPT ); Thu, 22 Jan 2015 12:18:50 -0500 Received: from mail-la0-f48.google.com ([209.85.215.48]:52499 "EHLO mail-la0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752530AbbAVRSs (ORCPT ); Thu, 22 Jan 2015 12:18:48 -0500 Message-ID: <54C130EA.2050505@gmail.com> Date: Thu, 22 Jan 2015 20:18:34 +0300 From: Dmitry Osipenko User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.3.0 MIME-Version: 1.0 To: Alexandre Courbot , Thierry Reding CC: Wolfram Sang , Stephen Warren , Laxman Dewangan , Ben Dooks , Bob Mottram , "linux-tegra@vger.kernel.org" , "linux-i2c@vger.kernel.org" , Linux Kernel Mailing List Subject: Re: [PATCH 1/2] i2c: tegra: Maintain CPU endianness References: <1421756555-20266-1-git-send-email-digetx@gmail.com> <20150122074001.GB427@ulmo> <54C115D1.10206@gmail.com> <54C12010.8040504@gmail.com> In-Reply-To: <54C12010.8040504@gmail.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 22.01.2015 19:06, Dmitry Osipenko пишет: > 22.01.2015 18:22, Dmitry Osipenko пишет: >> 22.01.2015 10:55, Alexandre Courbot пишет: >>> On Thu, Jan 22, 2015 at 4:40 PM, Thierry Reding >>> wrote: >>>> >>>> Should this not technically be le32_to_cpu() since the data originates >>>> from the I2C controller? >> >> No, i2c_readl returns value in CPU endianness, so it's correct. But for >> i2c_writel should be used le32_to_cpu(), since it takes value in CPU endianness. >> It's my overlook, V2 is coming. >> >>>> >>>> Why does this have to be initialized to 0 now? >>> >>> I suspect this is because we are going to memcpy less than 4 bytes >>> into it, but I cannot figure out how that memcpy if guaranteed to >>> produce the expected result for both endiannesses. >>> >> That's correct. Memcpy is working with bytes, so it doesn't care about >> endianness and produces expected result, since I2C message is char array. >> > I'll spend some more time reviewing, to see if nullifying should go as separate > patch. > Well, I2C_FIFO_STATUS returns 8-bit value. The rest of bits very likely to be RAZ, however I don't see anything on it in documentation. In that case it won't cause any problems with LE value and nullifying is only needed for BE mode. -- Dmitry