From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753145AbbAVPXM (ORCPT ); Thu, 22 Jan 2015 10:23:12 -0500 Received: from mail-la0-f54.google.com ([209.85.215.54]:41558 "EHLO mail-la0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752008AbbAVPXJ (ORCPT ); Thu, 22 Jan 2015 10:23:09 -0500 Message-ID: <54C115D1.10206@gmail.com> Date: Thu, 22 Jan 2015 18:22:57 +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> In-Reply-To: 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 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. -- Dmitry