linux-kernel - Re: [PATCH V2] fs/reiserfs/stree.c: remove obsolete _

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Message-ID: <1400106425.12666.6.camel@joe-AO725>
Date:	Wed, 14 May 2014 15:27:05 -0700
From:	Joe Perches <joe@...ches.com>
To:	Richard Weinberger <richard.weinberger@...il.com>
Cc:	Jan Kara <jack@...e.cz>, Fabian Frederick <fabf@...net.be>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	reiserfs-devel@...r.kernel.org, akpm <akpm@...ux-foundation.org>
Subject: Re: [PATCH V2] fs/reiserfs/stree.c: remove obsolete __constant

On Thu, 2014-05-15 at 00:08 +0200, Richard Weinberger wrote:
> On Thu, May 15, 2014 at 12:01 AM, Jan Kara <jack@...e.cz> wrote:
> > On Sat 03-05-14 22:33:24, Fabian Frederick wrote:
> >> __constant_cpu_to_le32 converted to cpu_to_le32
> >>
> >> Cc: reiserfs-devel@...r.kernel.org
> >> Cc: Andrew Morton <akpm@...ux-foundation.org>
> >> Signed-off-by: Fabian Frederick <fabf@...net.be>
> >   Just for my education, where have you learned that __constant_...
> > functions are obsolete?
> 
> IIRC checkpatch.pl barks if you use __constant_... outside of include/uapi/

I'd use not preferred and unnecessarily verbose more than obsolete.

These conversions are all tested with __builtin_constant_p
via indirection to macros like __swab32

include/uapi/linux/swab.h:#define __swab32(x)                           \
include/uapi/linux/swab.h-      (__builtin_constant_p((__u32)(x)) ?     \
include/uapi/linux/swab.h-      ___constant_swab32(x) :                 \
include/uapi/linux/swab.h-      __fswab32(x))

include/uapi/linux/swab.h:#define ___constant_swab32(x) ((__u32)(                               \
include/uapi/linux/swab.h-      (((__u32)(x) & (__u32)0x000000ffUL) << 24) |            \
include/uapi/linux/swab.h-      (((__u32)(x) & (__u32)0x0000ff00UL) <<  8) |            \
include/uapi/linux/swab.h-      (((__u32)(x) & (__u32)0x00ff0000UL) >>  8) |            \
include/uapi/linux/swab.h-      (((__u32)(x) & (__u32)0xff000000UL) >> 24)))


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