linux-kernel - Re: [PATCH 2/2] [2/2] extcon: optimising the check_mutually

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Message-id: <7520099.93351346399957499.JavaMail.weblogic@epml19>
Date:	Fri, 31 Aug 2012 07:59:18 +0000 (GMT)
From:	MyungJoo Ham <myungjoo.ham@...sung.com>
To:	anish kumar <anish198519851985@...il.com>,
	최찬우 <cw00.choi@...sung.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] [2/2] extcon: optimising the check_mutually_exclusive
 function

> From: anish kumar <anish198519851985@...il.com>
> 
> Rather than re-inventing the wheel we can use the hamming function
> to calculate the number of bits set to check for violation of
> exclusivity.
> 
> Signed-off-by: anish kumar <anish198519851985@...il.com>

Ah.. we've got such a convinient one. Thanks.

Singed-off-by: MyungJoo Ham <myungjoo.ham@...sung.com>


> ---
>  drivers/extcon/extcon-class.c |   14 +++++---------
>  1 files changed, 5 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/extcon/extcon-class.c b/drivers/extcon/extcon-class.c
> index e09a6c3..06df95a 100644
> --- a/drivers/extcon/extcon-class.c
> +++ b/drivers/extcon/extcon-class.c
> @@ -89,17 +89,13 @@ static int check_mutually_exclusive(struct extcon_dev *edev, u32 new_state)
>  		return 0;
>  
>  	for (i = 0; edev->mutually_exclusive[i]; i++) {
> -		int count = 0, j;
> +		int weight;
>  		u32 correspondants = new_state & edev->mutually_exclusive[i];
> -		u32 exp = 1;
> -
> -		for (j = 0; j < 32; j++) {
> -			if (exp & correspondants)
> -				count++;
> -			if (count > 1)
> -				return i + 1;
> -			exp <<= 1;
> -		}
> +
> +		/* calculate the total number of bits set */
> +		weight = hweight32(correspondants);
> +		if (weight > 1)
> +			return i + 1;
>  	}
>  
>  	return 0;
> -- 
> 1.7.1
> 
> 
> 
> 
>        
>   
>          
>