[alsa-devel] [PATCHv2 2/2] ASoC: simple-card: Fix bug of wrong decrement DT node's refcount

[Jean-Francois Moine]

On Mon, 1 Sep 2014 09:35:27 +0800
Xiubo Li <Li.Xiubo at freescale.com> wrote:

> DAI links's cpu_of_node's and codec_of_node's refcounts shouldn't
> be decremented immediately at the end of the probe() fucntion.
> Because we will still use them before the audio card is removed.

Right, but your patch seems a bit complicated. See below.

> 
> Signed-off-by: Xiubo Li <Li.Xiubo at freescale.com>
> ---
>  sound/soc/generic/simple-card.c | 52 ++++++++++++++++++++++-------------------
>  1 file changed, 28 insertions(+), 24 deletions(-)
> 
> diff --git a/sound/soc/generic/simple-card.c b/sound/soc/generic/simple-card.c
> index 9e170fe..08c5d7d 100644
> --- a/sound/soc/generic/simple-card.c
> +++ b/sound/soc/generic/simple-card.c
> @@ -307,6 +307,22 @@ dai_link_of_err:
>  	return ret;
>  }
>  
> +static inline void
> +asoc_simple_card_unref(const struct snd_soc_dai_link *dai_link,
> +		       int num_links)
> +{
> +	struct device_node *np;
> +
> +	while (num_links--) {
> +		np = dai_link[num_links].cpu_of_node;
> +		if (np)
> +			of_node_put(np);
> +		np = dai_link[num_links].codec_of_node;
> +		if (np)
> +			of_node_put(np);
> +	}
> +}
> +
>  static int asoc_simple_card_parse_of(struct device_node *node,
>  				     struct simple_card_data *priv,
>  				     struct device *dev,
> @@ -355,6 +371,7 @@ static int asoc_simple_card_parse_of(struct device_node *node,
>  							   dai_props + i,
>  							   false);
>  			if (ret < 0) {
> +				asoc_simple_card_unref(dai_link, i + 1);
>  				of_node_put(np);
>  				return ret;
>  			}
> @@ -374,27 +391,6 @@ static int asoc_simple_card_parse_of(struct device_node *node,
>  	return 0;
>  }
>  
> -/* update the reference count of the devices nodes at end of probe */
> -static int asoc_simple_card_unref(struct platform_device *pdev)
> -{
> -	struct snd_soc_card *card = platform_get_drvdata(pdev);
> -	struct snd_soc_dai_link *dai_link;
> -	struct device_node *np;
> -	int num_links;
> -
> -	for (num_links = 0, dai_link = card->dai_link;
> -	     num_links < card->num_links;
> -	     num_links++, dai_link++) {
> -		np = (struct device_node *) dai_link->cpu_of_node;
> -		if (np)
> -			of_node_put(np);
> -		np = (struct device_node *) dai_link->codec_of_node;
> -		if (np)
> -			of_node_put(np);
> -	}
> -	return 0;
> -}
> -
>  static int asoc_simple_card_probe(struct platform_device *pdev)
>  {
>  	struct simple_card_data *priv;
> @@ -441,7 +437,7 @@ static int asoc_simple_card_probe(struct platform_device *pdev)
>  		if (ret < 0) {
>  			if (ret != -EPROBE_DEFER)
>  				dev_err(dev, "parse error %d\n", ret);
> -			goto err;
> +			return ret;
>  		}
>  
>  	} else {
> @@ -483,11 +479,18 @@ static int asoc_simple_card_probe(struct platform_device *pdev)
>  
>  	ret = devm_snd_soc_register_card(&pdev->dev, &priv->snd_card);
>  
> -err:
> -	asoc_simple_card_unref(pdev);
>  	return ret;
>  }

The main problem is there: don't unref the nodes is no error.
Why not simply:
 
 	ret = devm_snd_soc_register_card(&pdev->dev, &priv->snd_card);
+	if (ret >= 0)
+		return ret;		/* success */
 
 err:
	asoc_simple_card_unref(pdev);
 	return ret;
 }

? Then, the above stuff is not needed.

> +static int asoc_simple_card_remove(struct platform_device *pdev)
> +{
> +	struct snd_soc_card *card = platform_get_drvdata(pdev);
> +
> +	asoc_simple_card_unref(card->dai_link, card->num_links);
> +
> +	return 0;
> +}
> +
>  static const struct of_device_id asoc_simple_of_match[] = {
>  	{ .compatible = "simple-audio-card", },
>  	{},
> @@ -501,6 +504,7 @@ static struct platform_driver asoc_simple_card = {
>  		.of_match_table = asoc_simple_of_match,
>  	},
>  	.probe = asoc_simple_card_probe,
> +	.remove = asoc_simple_card_remove,
>  };
>  
>  module_platform_driver(asoc_simple_card);

OK.

-- 
Ken ar c'hentañ	|	      ** Breizh ha Linux atav! **
Jef		|		http://moinejf.free.fr/