linux-kernel - Re: [PATCH -next] dmaengine: iop-adma: Fix -Wint-to-pointer-cast build warning

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Message-ID: <20200805131205.GY12965@vkoul-mobl>
Date:   Wed, 5 Aug 2020 18:42:05 +0530
From:   Vinod Koul <vkoul@...nel.org>
To:     YueHaibing <yuehaibing@...wei.com>
Cc:     dan.j.williams@...el.com, dmaengine@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH -next] dmaengine: iop-adma: Fix -Wint-to-pointer-cast
 build warning

On 03-08-20, 22:10, YueHaibing wrote:
> drivers/dma/iop-adma.c:447:13: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
> drivers/dma/iop-adma.c:449:4: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast]
> drivers/dma/iop-adma.c:1301:3: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
> 
> Use void* for dma_desc_pool_virt, dma_addr_t for dma_desc_pool,
> and use %pad to print dma_addr_t.
> 
> Signed-off-by: YueHaibing <yuehaibing@...wei.com>
> ---
>  drivers/dma/iop-adma.c | 17 ++++++++---------
>  1 file changed, 8 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/dma/iop-adma.c b/drivers/dma/iop-adma.c
> index 3350bffb2e93..8e17e4405959 100644
> --- a/drivers/dma/iop-adma.c
> +++ b/drivers/dma/iop-adma.c
> @@ -415,7 +415,8 @@ static void iop_chan_start_null_xor(struct iop_adma_chan *iop_chan);
>   * */
>  static int iop_adma_alloc_chan_resources(struct dma_chan *chan)
>  {
> -	char *hw_desc;
> +	void *hw_desc;
> +	dma_addr_t dma_desc;
>  	int idx;
>  	struct iop_adma_chan *iop_chan = to_iop_adma_chan(chan);
>  	struct iop_adma_desc_slot *slot = NULL;
> @@ -436,17 +437,16 @@ static int iop_adma_alloc_chan_resources(struct dma_chan *chan)
>  				" %d descriptor slots", idx);
>  			break;
>  		}
> -		hw_desc = (char *) iop_chan->device->dma_desc_pool_virt;
> -		slot->hw_desc = (void *) &hw_desc[idx * IOP_ADMA_SLOT_SIZE];
> +		hw_desc = iop_chan->device->dma_desc_pool_virt;
> +		slot->hw_desc = hw_desc + idx * IOP_ADMA_SLOT_SIZE;

So you want to pointer arithmetic on a void pointer !

Are you sure math is correct here and will work on different compilers?

>  
>  		dma_async_tx_descriptor_init(&slot->async_tx, chan);
>  		slot->async_tx.tx_submit = iop_adma_tx_submit;
>  		INIT_LIST_HEAD(&slot->tx_list);
>  		INIT_LIST_HEAD(&slot->chain_node);
>  		INIT_LIST_HEAD(&slot->slot_node);
> -		hw_desc = (char *) iop_chan->device->dma_desc_pool;
> -		slot->async_tx.phys =
> -			(dma_addr_t) &hw_desc[idx * IOP_ADMA_SLOT_SIZE];
> +		dma_desc = iop_chan->device->dma_desc_pool;
> +		slot->async_tx.phys = dma_desc + idx * IOP_ADMA_SLOT_SIZE;
>  		slot->idx = idx;
>  
>  		spin_lock_bh(&iop_chan->lock);
> @@ -1296,9 +1296,8 @@ static int iop_adma_probe(struct platform_device *pdev)
>  		goto err_free_adev;
>  	}
>  
> -	dev_dbg(&pdev->dev, "%s: allocated descriptor pool virt %p phys %p\n",
> -		__func__, adev->dma_desc_pool_virt,
> -		(void *) adev->dma_desc_pool);
> +	dev_dbg(&pdev->dev, "%s: allocated descriptor pool virt %p phys %pad\n",
> +		__func__, adev->dma_desc_pool_virt, &adev->dma_desc_pool);
>  
>  	adev->id = plat_data->hw_id;
>  
> -- 
> 2.17.1
> 

-- 
~Vinod