From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932276Ab0CXSxR (ORCPT ); Wed, 24 Mar 2010 14:53:17 -0400 Received: from mail3.caviumnetworks.com ([12.108.191.235]:1052 "EHLO mail3.caviumnetworks.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932645Ab0CXSxP (ORCPT ); Wed, 24 Mar 2010 14:53:15 -0400 Message-ID: <4BAA5F99.3050904@caviumnetworks.com> Date: Wed, 24 Mar 2010 11:53:13 -0700 From: David Daney User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.8) Gecko/20100301 Fedora/3.0.3-1.fc12 Thunderbird/3.0.3 MIME-Version: 1.0 To: Geert Uytterhoeven CC: Andrew Morton , Joakim Tjernlund , LKML Subject: Re: [PATCH] [RFC] #define __BYTE_ORDER References: <1268849455-19503-1-git-send-email-Joakim.Tjernlund@transmode.se> <20100324112106.c8e7b96d.akpm@linux-foundation.org> <10f740e81003241137y382d155fnb777344d3af25f03@mail.gmail.com> In-Reply-To: <10f740e81003241137y382d155fnb777344d3af25f03@mail.gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-OriginalArrivalTime: 24 Mar 2010 18:53:14.0016 (UTC) FILETIME=[41E4FA00:01CACB83] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/24/2010 11:37 AM, Geert Uytterhoeven wrote: > On Wed, Mar 24, 2010 at 19:21, Andrew Morton wrote: >> On Wed, 17 Mar 2010 19:10:55 +0100 >> Joakim Tjernlund wrote: >> >>> Linux does not define __BYTE_ORDER in its endian header files >>> which makes some header files bend backwards to get at the >>> current endian. Lets #define __BYTE_ORDER in big_endian.h/litte_endian.h >>> to make it easier for header files that are used in user space too. >> >> I don't get it. Why not nuke __BYTE_ORDER altogether and do `#ifdef >> __LITTLE_ENDIAN' and `#ifdef __BIG_ENDIAN' everywhere? > > Because in userspace the convention is that > 1. _both_ __LITTLE_ENDIAN and __BIG_ENDIAN are defined, > 2. you have to test for e.g. __BYTE_ORDER == __BIG_ENDIAN. > I have stumbled on this issue as well. However, consider this: If you make such a change, then you will start to see: #if __BYTE_ORDER == __BIG_ENDIAN appearing in kernel source code. Do we want two different endian checking idioms in the kernel? Or would it be just a single idiom, but one that is different than the status quo? The only time I can see that it makes a difference is if you want to share things like driver source code files between in-kernel drivers and userspace. A discussion of which, would probably provoke much discussion. David Daney