From mboxrd@z Thu Jan  1 00:00:00 1970
From: Patrick McHardy <kaber@trash.net>
Subject: Re: [PATCH 2/4] dsmark: get rid of trivial function
Date: Mon, 21 Jan 2008 01:16:32 +0100
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References: <20080120130542.16720b45@deepthought> <20080120132550.056370c0@deepthought>
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Cc: David Miller <davem@davemloft.net>, netdev@vger.kernel.org
To: Stephen Hemminger <shemminger@vyatta.com>
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Stephen Hemminger wrote:
> Replace loop in dsmark_valid_indices with equivalent bit math.
> 
> Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
> 
> --- a/net/sched/sch_dsmark.c	2008-01-20 13:07:58.000000000 -0800
> +++ b/net/sched/sch_dsmark.c	2008-01-20 13:22:54.000000000 -0800
> @@ -45,13 +45,8 @@ struct dsmark_qdisc_data {
>  
>  static inline int dsmark_valid_indices(u16 indices)
>  {
> -	while (indices != 1) {
> -		if (indices & 1)
> -			return 0;
> -		indices >>= 1;
> -	}
> -
> -	return 1;
> +	/* Must have only one bit set */
> +	return (indices & (indices - 1)) == 0;


hweight seems easier to understand, it took me a bit
to realize that the comment matches the code :)