linux-kernel - Re: [PATCH] DMA: ste_dma40: use a power of 2 check

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Date:	Mon, 23 Sep 2013 09:51:43 +0530
From:	Vinod Koul <vinod.koul@...el.com>
To:	Guennadi Liakhovetski <g.liakhovetski@....de>
Cc:	linux-kernel@...r.kernel.org,
	Linus Walleij <linus.walleij@...aro.org>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] DMA: ste_dma40: use a power of 2 check

On Wed, Sep 18, 2013 at 09:33:08AM +0200, Guennadi Liakhovetski wrote:
> dst_addr_width and src_addr_width should be a power of 2. Currently the 
> driver checks, that they both lie between 1 and 8 and that they are eqal 
typo								     ^^^^^
> to 1 or even. This however leaves an invalid value of 6 uncaught. Use an 
> explicit power of 2 check instead.
> 
Applied, with typo fix above..

~Vinod
> Signed-off-by: Guennadi Liakhovetski <g.liakhovetski+renesas@...il.com>
> ---
> 
> Compile tested only. I think 6 is an invalid value in this case, and since 
> you check for odd calues, it seems to me that any value can be supplied 
> here, so, looks like a power of 2 test is a better match for this.
> 
> diff --git a/drivers/dma/ste_dma40.c b/drivers/dma/ste_dma40.c
> index 82d2b97..3d5e4ee 100644
> --- a/drivers/dma/ste_dma40.c
> +++ b/drivers/dma/ste_dma40.c
> @@ -14,6 +14,7 @@
>  #include <linux/platform_device.h>
>  #include <linux/clk.h>
>  #include <linux/delay.h>
> +#include <linux/log2.h>
>  #include <linux/pm.h>
>  #include <linux/pm_runtime.h>
>  #include <linux/err.h>
> @@ -2796,8 +2797,8 @@ static int d40_set_runtime_config(struct dma_chan *chan,
>  	    src_addr_width >  DMA_SLAVE_BUSWIDTH_8_BYTES   ||
>  	    dst_addr_width <= DMA_SLAVE_BUSWIDTH_UNDEFINED ||
>  	    dst_addr_width >  DMA_SLAVE_BUSWIDTH_8_BYTES   ||
> -	    ((src_addr_width > 1) && (src_addr_width & 1)) ||
> -	    ((dst_addr_width > 1) && (dst_addr_width & 1)))
> +	    !is_power_of_2(src_addr_width) ||
> +	    !is_power_of_2(dst_addr_width))
>  		return -EINVAL;
>  
>  	cfg->src_info.data_width = src_addr_width;

-- 
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