linux-kernel - Re: [PATCH 2/5] arc: use for_each

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Message-ID: <C2D7FE5348E1B147BCA15975FBA230756659D5E7@IN01WEMBXB.internal.synopsys.com>
Date:	Fri, 1 May 2015 08:40:12 +0000
From:	Vineet Gupta <Vineet.Gupta1@...opsys.com>
To:	Akinobu Mita <akinobu.mita@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>
CC:	"linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>
Subject: Re: [PATCH 2/5] arc: use for_each_sg()

On Friday 01 May 2015 12:17 PM, Akinobu Mita wrote:
> Since arc doesn't select ARCH_HAS_SG_CHAIN, it is not necessary to
> use for_each_sg() in order to loop over each sg element.  But this can
> help find problems with drivers that do not properly initialize their
> sg tables when CONFIG_DEBUG_SG is enabled.
> 
> Signed-off-by: Akinobu Mita <akinobu.mita@...il.com>
> Cc: Vineet Gupta <vgupta@...opsys.com>
> Cc: linux-arch@...r.kernel.org

Looks fine to me. However it must be noted (perhaps add to change log) that this
will lead to different generated code as sg_next() is a function call etc. So this
change is strictly not equivalent to what we had before.

Acked-by: Vineet Gupta <vgupta@...opsys.com>

Thx,
-Vineet


> ---
>  arch/arc/include/asm/dma-mapping.h | 12 +++++++-----
>  1 file changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/arc/include/asm/dma-mapping.h b/arch/arc/include/asm/dma-mapping.h
> index 45b8e0c..f787894 100644
> --- a/arch/arc/include/asm/dma-mapping.h
> +++ b/arch/arc/include/asm/dma-mapping.h
> @@ -178,22 +178,24 @@ dma_sync_single_range_for_device(struct device *dev, dma_addr_t dma_handle,
>  }
>  
>  static inline void
> -dma_sync_sg_for_cpu(struct device *dev, struct scatterlist *sg, int nelems,
> +dma_sync_sg_for_cpu(struct device *dev, struct scatterlist *sglist, int nelems,
>  		    enum dma_data_direction dir)
>  {
>  	int i;
> +	struct scatterlist *sg;
>  
> -	for (i = 0; i < nelems; i++, sg++)
> +	for_each_sg(sglist, sg, nelems, i)
>  		_dma_cache_sync((unsigned int)sg_virt(sg), sg->length, dir);
>  }
>  
>  static inline void
> -dma_sync_sg_for_device(struct device *dev, struct scatterlist *sg, int nelems,
> -		       enum dma_data_direction dir)
> +dma_sync_sg_for_device(struct device *dev, struct scatterlist *sglist,
> +		       int nelems, enum dma_data_direction dir)
>  {
>  	int i;
> +	struct scatterlist *sg;
>  
> -	for (i = 0; i < nelems; i++, sg++)
> +	for_each_sg(sglist, sg, nelems, i)
>  		_dma_cache_sync((unsigned int)sg_virt(sg), sg->length, dir);
>  }
>  
> 

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