linux-kernel - Re: [PATCH 4/5] rt2x00: Compiler warning unmasked by fix of BUILD_BUG

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Date:	Mon, 01 Sep 2008 16:27:20 +0300
From:	Benny Halevy <bhalevy@...asas.com>
To:	Boaz Harrosh <bharrosh@...asas.com>
CC:	Ingo Molnar <mingo@...e.hu>, Rusty Russell <rusty@...tcorp.com.au>,
	"David S. Miller" <davem@...emloft.net>,
	Ivo van Doorn <IvDoorn@...il.com>,
	"John W. Linville" <linville@...driver.com>,
	Alexey Dobriyan <adobriyan@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Theodore Tso <tytso@....edu>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Jan Beulich <jbeulich@...ell.com>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/5] rt2x00: Compiler warning unmasked by fix of BUILD_BUG_ON

On Sep. 01, 2008, 16:21 +0300, Boaz Harrosh <bharrosh@...asas.com> wrote:
> A "Set" of the sign-bit in an "&" operation causes a compiler warning.
> Make calculations unsigned.
> 
> [ The warning was masked by the use of (void)() cast in the old
>   BUILD_BUG_ON() ]
> 
> Signed-off-by: Boaz Harrosh <bharrosh@...asas.com>
> TO: Ivo van Doorn <IvDoorn@...il.com>
> TO: John W. Linville <linville@...driver.com>
> CC: Ingo Molnar <mingo@...e.hu>
> CC: Rusty Russell <rusty@...tcorp.com.au>
> ---
>  drivers/net/wireless/rt2x00/rt2x00reg.h |    4 ++--
>  1 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/wireless/rt2x00/rt2x00reg.h b/drivers/net/wireless/rt2x00/rt2x00reg.h
> index 7e88ce5..c0e8706 100644
> --- a/drivers/net/wireless/rt2x00/rt2x00reg.h
> +++ b/drivers/net/wireless/rt2x00/rt2x00reg.h
> @@ -134,8 +134,8 @@ struct rt2x00_field32 {
>   * Note that we cannot use the is_power_of_2() function since this
>   * check must be done at compile-time.
>   */
> -#define is_power_of_two(x)	( !((x) & ((x)-1)) )
> -#define low_bit_mask(x)		( ((x)-1) & ~(x) )
> +#define is_power_of_two(x)	( !((unsigned)(x) & ((x)-1)) )
> +#define low_bit_mask(x)		( ((unsigned)(x)-1) & ~(x) )

Why not unsigned long?

Benny

>  #define is_valid_mask(x)	is_power_of_two(1 + (x) + low_bit_mask(x))
>  
>  /*
> --
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