From: David Daney <ddaney@caviumnetworks.com>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Joakim Tjernlund <Joakim.Tjernlund@transmode.se>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] [RFC] #define __BYTE_ORDER
Date: Wed, 24 Mar 2010 11:53:13 -0700 [thread overview]
Message-ID: <4BAA5F99.3050904@caviumnetworks.com> (raw)
In-Reply-To: <10f740e81003241137y382d155fnb777344d3af25f03@mail.gmail.com>
On 03/24/2010 11:37 AM, Geert Uytterhoeven wrote:
> On Wed, Mar 24, 2010 at 19:21, Andrew Morton<akpm@linux-foundation.org> wrote:
>> On Wed, 17 Mar 2010 19:10:55 +0100
>> Joakim Tjernlund<Joakim.Tjernlund@transmode.se> 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
next prev parent reply other threads:[~2010-03-24 18:53 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-03-17 18:10 [PATCH] [RFC] #define __BYTE_ORDER Joakim Tjernlund
2010-03-24 18:21 ` Andrew Morton
2010-03-24 18:37 ` Geert Uytterhoeven
2010-03-24 18:51 ` Andrew Morton
2010-03-24 18:53 ` David Daney [this message]
2010-03-24 21:55 ` Joakim Tjernlund
2010-03-24 21:45 ` Joakim Tjernlund
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