linux-kernel - Re: [PATCH] dmaengine: fsl-edma: use struct

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Message-ID: <20190106194059.GA2120@jerusalem>
Date:   Sun, 6 Jan 2019 20:40:59 +0100
From:   Angelo Dureghello <angelo@...am.it>
To:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Cc:     Dan Williams <dan.j.williams@...el.com>,
        Vinod Koul <vkoul@...nel.org>, dmaengine@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] dmaengine: fsl-edma: use struct_size() in kzalloc()

On Fri, Jan 04, 2019 at 03:25:45PM -0600, Gustavo A. R. Silva wrote:
> One of the more common cases of allocation size calculations is finding the
> size of a structure that has a zero-sized array at the end, along with memory
> for some number of elements for that array. For example:
> 
> struct foo {
>     int stuff;
>     void *entry[];
> };
> 
> instance = kzalloc(sizeof(struct foo) + sizeof(void *) * count, GFP_KERNEL);
> 
> Instead of leaving these open-coded and prone to type mistakes, we can now
> use the new struct_size() helper:
> 
> instance = kzalloc(struct_size(instance, entry, count), GFP_KERNEL);
> 
> This code was detected with the help of Coccinelle.
> 
> Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
> ---
>  drivers/dma/fsl-edma-common.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/drivers/dma/fsl-edma-common.c b/drivers/dma/fsl-edma-common.c
> index 8876c4c1bb2c..fe529100674f 100644
> --- a/drivers/dma/fsl-edma-common.c
> +++ b/drivers/dma/fsl-edma-common.c
> @@ -339,9 +339,7 @@ static struct fsl_edma_desc *fsl_edma_alloc_desc(struct fsl_edma_chan *fsl_chan,
>  	struct fsl_edma_desc *fsl_desc;
>  	int i;
>  
> -	fsl_desc = kzalloc(sizeof(*fsl_desc) +
> -			   sizeof(struct fsl_edma_sw_tcd) *
> -			   sg_len, GFP_NOWAIT);
> +	fsl_desc = kzalloc(struct_size(fsl_desc, tcd, sg_len), GFP_NOWAIT);
>  	if (!fsl_desc)
>  		return NULL;
>

Tested-by: Angelo Dureghello <angelo@...am.it>

  
> -- 
> 2.20.1
>