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Date: Wed, 29 Mar 2017 14:36:56 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Niklas =?ISO-8859-1?Q?S=F6derlund?= 
        <niklas.soderlund+renesas@ragnatech.se>,
        Jessica Yu <jeyu@redhat.com>, Johannes Berg <johannes.berg@intel.com>,
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        Larry Finger <Larry.Finger@lwfinger.net>, linux-kernel@vger.kernel.org,
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        Peter Zijlstra <peterz@infradead.org>,
        Luis de Bethencourt <luisbg@osg.samsung.com>,
        Josh Triplett <josh@joshtriplett.org>
Subject: Re: [PATCH] kernel.h: add IS_PTR_ALIGNED() macro
Message-Id: <20170329143656.d89a2f139316df3f39a91db9@linux-foundation.org>
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On Wed, 29 Mar 2017 19:22:10 +0900 Masahiro Yamada <yamada.masahiro@socionext.com> wrote:

> We often check if a pointer has a specific alignment.  Because the
> '&' (bitwise AND) operator cannot take a pointer for the operand,
> so we need a cast like, IS_ALIGNED((unsigned long)p, a).
> 
> IS_PTR_ALIGNED will be useful as a shorthand.
> 
> ...
>
> --- a/include/linux/kernel.h
> +++ b/include/linux/kernel.h
> @@ -50,6 +50,7 @@
>  #define __ALIGN_MASK(x, mask)	__ALIGN_KERNEL_MASK((x), (mask))
>  #define PTR_ALIGN(p, a)		((typeof(p))ALIGN((unsigned long)(p), (a)))
>  #define IS_ALIGNED(x, a)		(((x) & ((typeof(x))(a) - 1)) == 0)
> +#define IS_PTR_ALIGNED(p, a)		(IS_ALIGNED((unsigned long)p, a))
>  
>  /* generic data direction definitions */
>  #define READ			0

It would be nice to see some conversions which actually use this new
macro.