linux-kernel - Re: [RFC PATCH 1/6] kenrel.h: add ALIGN_OF_LAST

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Date:	Tue, 20 Mar 2012 12:32:14 +0100
From:	"Michal Nazarewicz" <mina86@...a86.com>
To:	"Christoph Lameter" <cl@...ux-foundation.org>,
	"Pekka Enberg" <penberg@...nel.org>,
	"Matt Mackall" <mpm@...enic.com>, "Tejun Heo" <tj@...nel.org>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	"Lai Jiangshan" <laijs@...fujitsu.com>
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [RFC PATCH 1/6] kenrel.h: add ALIGN_OF_LAST_BIT()

On Tue, 20 Mar 2012 11:21:19 +0100, Lai Jiangshan <laijs@...fujitsu.com> wrote:

> Get the biggest 2**y that x % (2**y) == 0 for the align value.
>
> Signed-off-by: Lai Jiangshan <laijs@...fujitsu.com>
> ---
>  include/linux/kernel.h |    2 ++
>  1 files changed, 2 insertions(+), 0 deletions(-)
>
> diff --git a/include/linux/kernel.h b/include/linux/kernel.h
> index 5113462..2c439dc 100644
> --- a/include/linux/kernel.h
> +++ b/include/linux/kernel.h
> @@ -44,6 +44,8 @@
>  #define PTR_ALIGN(p, a)		((typeof(p))ALIGN((unsigned long)(p), (a)))
>  #define IS_ALIGNED(x, a)		(((x) & ((typeof(x))(a) - 1)) == 0)
>+#define ALIGN_OF_LAST_BIT(x)	((((x)^((x) - 1))>>1) + 1)

Wouldn't ALIGNMENT() be less confusing? After all, that's what this macro is
calculating, right? Alignment of given address.

> +
>  #define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]) + __must_be_array(arr))
> /*


-- 
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.o. | Liege of Serenely Enlightened Majesty of      o' \,=./ `o
..o | Computer Science,  Michał “mina86” Nazarewicz    (o o)
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