linux-kernel - Re: [PATCH] dmaengine: mxs-dma: Add check for dma_set_max_seg

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Date: Wed, 24 Apr 2024 00:07:01 -0400
From: Frank Li <Frank.li@....com>
To: Ma Ke <make_ruc2021@....com>
Cc: vkoul@...nel.org, shawnguo@...nel.org, s.hauer@...gutronix.de,
	kernel@...gutronix.de, festevam@...il.com,
	dmaengine@...r.kernel.org, imx@...ts.linux.dev,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] dmaengine: mxs-dma: Add check for dma_set_max_seg_size()

On Tue, Apr 23, 2024 at 10:32:05PM +0800, Ma Ke wrote:
> To avoid the failure of dma_set_max_seg_size(), we should check the
> return value of the dma_set_max_seg_size().

Check return value of dma_set_max_seg_size() in case it return error.

> 
> Signed-off-by: Ma Ke <make_ruc2021@....com>
> ---
>  drivers/dma/mxs-dma.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/dma/mxs-dma.c b/drivers/dma/mxs-dma.c
> index cfb9962417ef..90cbb9b04b02 100644
> --- a/drivers/dma/mxs-dma.c
> +++ b/drivers/dma/mxs-dma.c
> @@ -798,7 +798,9 @@ static int mxs_dma_probe(struct platform_device *pdev)
>  	mxs_dma->dma_device.dev = &pdev->dev;
>  
>  	/* mxs_dma gets 65535 bytes maximum sg size */
> -	dma_set_max_seg_size(mxs_dma->dma_device.dev, MAX_XFER_BYTES);
> +	ret = dma_set_max_seg_size(mxs_dma->dma_device.dev, MAX_XFER_BYTES);
> +	if (ret)
> +		return ret;

How error happen? 

static inline int dma_set_max_seg_size(struct device *dev, unsigned int size)
{
	if (dev->dma_parms) {
		dev->dma_parms->max_segment_size = size;
		return 0;
	}
	return -EIO;
}

Only possible dev->dma_parms is null. but mxs-dma is platform device, it
point to platform's dma_parms field. Look like impossible it is null.

Frank 



>  
>  	mxs_dma->dma_device.device_alloc_chan_resources = mxs_dma_alloc_chan_resources;
>  	mxs_dma->dma_device.device_free_chan_resources = mxs_dma_free_chan_resources;
> -- 
> 2.37.2
>