Re: [PATCH V3] net: ethernet: ti: netcp: Standardize knav_dma_open_channel to return NULL on error

[Jacob Keller <jacob.e.keller@intel.com>]

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On 10/29/2025 6:23 AM, Nishanth Menon wrote:
> diff --git a/drivers/soc/ti/knav_dma.c b/drivers/soc/ti/knav_dma.c
> index a25ebe6cd503..e69f0946de29 100644
> --- a/drivers/soc/ti/knav_dma.c
> +++ b/drivers/soc/ti/knav_dma.c
> @@ -402,7 +402,7 @@ static int of_channel_match_helper(struct device_node *np, const char *name,
>   * @name:	slave channel name
>   * @config:	dma configuration parameters
>   *
> - * Returns pointer to appropriate DMA channel on success or error.
> + * Returns pointer to appropriate DMA channel on success or NULL on error.
>   */
>  void *knav_dma_open_channel(struct device *dev, const char *name,
>  					struct knav_dma_cfg *config)
> @@ -414,13 +414,13 @@ void *knav_dma_open_channel(struct device *dev, const char *name,
>  
>  	if (!kdev) {
>  		pr_err("keystone-navigator-dma driver not registered\n");
> -		return (void *)-EINVAL;
> +		return NULL;
>  	}
>  
>  	chan_num = of_channel_match_helper(dev->of_node, name, &instance);
>  	if (chan_num < 0) {
>  		dev_err(kdev->dev, "No DMA instance with name %s\n", name);
> -		return (void *)-EINVAL;
> +		return NULL;
>  	}
>  
>  	dev_dbg(kdev->dev, "initializing %s channel %d from DMA %s\n",
> @@ -431,7 +431,7 @@ void *knav_dma_open_channel(struct device *dev, const char *name,
>  	if (config->direction != DMA_MEM_TO_DEV &&
>  	    config->direction != DMA_DEV_TO_MEM) {
>  		dev_err(kdev->dev, "bad direction\n");
> -		return (void *)-EINVAL;
> +		return NULL;
>  	}
>  
>  	/* Look for correct dma instance */
> @@ -443,7 +443,7 @@ void *knav_dma_open_channel(struct device *dev, const char *name,
>  	}
>  	if (!dma) {
>  		dev_err(kdev->dev, "No DMA instance with name %s\n", instance);
> -		return (void *)-EINVAL;
> +		return NULL;
>  	}
>  
>  	/* Look for correct dma channel from dma instance */
> @@ -463,14 +463,14 @@ void *knav_dma_open_channel(struct device *dev, const char *name,
>  	if (!chan) {
>  		dev_err(kdev->dev, "channel %d is not in DMA %s\n",
>  				chan_num, instance);
> -		return (void *)-EINVAL;
> +		return NULL;
>  	}
>  
>  	if (atomic_read(&chan->ref_count) >= 1) {
>  		if (!check_config(chan, config)) {
>  			dev_err(kdev->dev, "channel %d config miss-match\n",
>  				chan_num);
> -			return (void *)-EINVAL;
> +			return NULL;
>  		}
>  	}
>  

Since we were basically always returning -EINVAL that seems reasonable
to just switch to NULL instead.

Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>

Thanks,
Jake

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