Re: [PATCH] staging: axis-fifo: refactor device tree parsing

[Dan Carpenter <dan.carpenter@linaro.org>]

On Sat, Jan 31, 2026 at 11:05:17AM -0300, Gustavo Piaz da Silva wrote:
> Refactor the device tree parsing logic in axis_fifo_probe() to reduce code duplication and improve readability.
> 
> Create a helper function axis_fifo_get_u32() to handle property reading and error checking, replacing repetitive of_property_read_u32() calls.
> 
> This change reduces the verbosity of the probe function and consolidates error logging for missing properties.
> 

Line wrap the commit message at 72 characters.

> Signed-off-by: Gustavo Piaz da Silva <gustavopiazdasilva2102@gmail.com>
> ---
>  drivers/staging/axis-fifo/axis-fifo.c | 76 +++++++++------------------
>  1 file changed, 24 insertions(+), 52 deletions(-)
> 
> diff --git a/drivers/staging/axis-fifo/axis-fifo.c b/drivers/staging/axis-fifo/axis-fifo.c
> index 509d620d6ce7..258bb95f03d4 100644
> --- a/drivers/staging/axis-fifo/axis-fifo.c
> +++ b/drivers/staging/axis-fifo/axis-fifo.c
> @@ -482,68 +482,41 @@ static void axis_fifo_debugfs_init(struct axis_fifo *fifo)
>  			    &axis_fifo_debugfs_regs_fops);
>  }
>  
> -static int axis_fifo_parse_dt(struct axis_fifo *fifo)
> +static int axis_fifo_get_u32(struct axis_fifo *fifo, const char *prop, u32 *val)
>  {
> -	int ret;
> -	unsigned int value;
> -	struct device_node *node = fifo->dt_device->of_node;
> +	int ret = of_property_read_u32(fifo->dt_device->of_node, prop, val);
>  
> -	ret = of_property_read_u32(node, "xlnx,axi-str-rxd-tdata-width",
> -				   &value);
>  	if (ret) {
> -		dev_err(fifo->dt_device, "missing xlnx,axi-str-rxd-tdata-width property\n");
> -		goto end;
> -	} else if (value != 32) {
> -		dev_err(fifo->dt_device, "xlnx,axi-str-rxd-tdata-width only supports 32 bits\n");
> -		ret = -EIO;
> -		goto end;
> +		dev_err(fifo->dt_device, "missing %s property\n", prop);
> +		return ret;
>  	}
> +	return 0;
> +}
>  
> -	ret = of_property_read_u32(node, "xlnx,axi-str-txd-tdata-width",
> -				   &value);
> -	if (ret) {
> -		dev_err(fifo->dt_device, "missing xlnx,axi-str-txd-tdata-width property\n");
> -		goto end;
> -	} else if (value != 32) {
> -		dev_err(fifo->dt_device, "xlnx,axi-str-txd-tdata-width only supports 32 bits\n");
> -		ret = -EIO;
> -		goto end;
> -	}
> +static int axis_fifo_parse_dt(struct axis_fifo *fifo)
> +{
> +	u32 width;
>  
> -	ret = of_property_read_u32(node, "xlnx,rx-fifo-depth",
> -				   &fifo->rx_fifo_depth);
> -	if (ret) {
> -		dev_err(fifo->dt_device, "missing xlnx,rx-fifo-depth property\n");
> -		ret = -EIO;
> +	if (axis_fifo_get_u32(fifo, "xlnx,axi-str-rxd-tdata-width", &width) || width != 32)
>  		goto end;
> -	}
> -
> -	ret = of_property_read_u32(node, "xlnx,tx-fifo-depth",
> -				   &fifo->tx_fifo_depth);
> -	if (ret) {
> -		dev_err(fifo->dt_device, "missing xlnx,tx-fifo-depth property\n");
> -		ret = -EIO;
> +	if (axis_fifo_get_u32(fifo, "xlnx,axi-str-txd-tdata-width", &width) || width != 32)
>  		goto end;

This goto end stuff is weird.  I get why you did it (because the error
message is the same both times).  But it's like I have to think about
why these have a goto and the others are direct returns and I don't like
that.  I think I probably would have just changed the strings to be
slightly different which solves the problem in a different way.

> -	}
>  
> -	ret = of_property_read_u32(node, "xlnx,use-rx-data",
> -				   &fifo->has_rx_fifo);
> -	if (ret) {
> -		dev_err(fifo->dt_device, "missing xlnx,use-rx-data property\n");
> -		ret = -EIO;
> -		goto end;
> -	}
> +	if (axis_fifo_get_u32(fifo, "xlnx,rx-fifo-depth", &fifo->rx_fifo_depth))
> +		return -EIO;
> +	if (axis_fifo_get_u32(fifo, "xlnx,tx-fifo-depth", &fifo->tx_fifo_depth))
> +		return -EIO;
>  
> -	ret = of_property_read_u32(node, "xlnx,use-tx-data",
> -				   &fifo->has_tx_fifo);
> -	if (ret) {
> -		dev_err(fifo->dt_device, "missing xlnx,use-tx-data property\n");
> -		ret = -EIO;
> -		goto end;
> -	}
> +	if (axis_fifo_get_u32(fifo, "xlnx,use-rx-data", (u32 *)&fifo->has_rx_fifo))
> +		return -EIO;
> +	if (axis_fifo_get_u32(fifo, "xlnx,use-tx-data", (u32 *)&fifo->has_tx_fifo))
> +		return -EIO;

These casts weren't there in the original code.  I hate these casts.
We could just change the type from int to u32.  Or we could leave the
casts out like the original code did.

> +
> +	return 0;
>  
>  end:
> -	return ret;
> +	dev_err(fifo->dt_device, "tdata-width only supports 32 bits\n");
> +	return -EIO;
>  }
>  
>  static int axis_fifo_probe(struct platform_device *pdev)
> @@ -646,8 +619,7 @@ static int axis_fifo_probe(struct platform_device *pdev)
>  
>  static void axis_fifo_remove(struct platform_device *pdev)
>  {
> -	struct device *dev = &pdev->dev;
> -	struct axis_fifo *fifo = dev_get_drvdata(dev);
> +	struct axis_fifo *fifo = platform_get_drvdata(pdev);


This is unrelated.

regards,
dan carpenter

>  
>  	debugfs_remove(fifo->debugfs_dir);
>  	misc_deregister(&fifo->miscdev);
> -- 
> 2.52.0
>