linux-kernel - Re: [PATCH v3 1/4] ASoc: kirkwood: simplify probe error

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Message-ID: <20130803124652.GY23006@n2100.arm.linux.org.uk>
Date:	Sat, 3 Aug 2013 13:46:52 +0100
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Jean-Francois Moine <moinejf@...e.fr>
Cc:	Liam Girdwood <lgirdwood@...il.com>,
	Mark Brown <broonie@...nel.org>,
	Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.de>,
	Rob Herring <rob.herring@...xeda.com>,
	alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
	devicetree@...r.kernel.org
Subject: Re: [PATCH v3 1/4] ASoc: kirkwood: simplify probe error

On Wed, Jul 31, 2013 at 08:17:39AM +0200, Jean-Francois Moine wrote:
> The function kirkwood_i2s_dev_remove() may be used when probe fails.

Looking at this deeper, I'm not happy with this.

> +static int kirkwood_i2s_dev_remove(struct platform_device *pdev)
> +{
> +	struct kirkwood_dma_data *priv = dev_get_drvdata(&pdev->dev);
> +
> +	snd_soc_unregister_component(&pdev->dev);
...
> @@ -519,30 +532,17 @@ static int kirkwood_i2s_dev_probe(struct platform_device *pdev)
>  
>  	err = snd_soc_register_component(&pdev->dev, &kirkwood_i2s_component,
>  					 soc_dai, 1);
> +	if (err) {
> +		dev_err(&pdev->dev, "snd_soc_register_component failed\n");
> +		goto fail;
> +	}
> +	return 0;
>  
> +fail:
> +	kirkwood_i2s_dev_remove(pdev);

What this means is that if snd_soc_register_component() fails, we end
up calling snd_soc_unregister_component().  This may be fine with the
way snd_soc_unregister_component() is currently implemented, but you're
making the assumption that it's fine to call snd_soc_unregister_component()
for a device which hasn't been registered.  Technically, this is a
layering violation, which makes this change fragile if the behaviour
of snd_soc_unregister_component() changes in the future.

For the sake of two calls in the error path, I don't think the benefits
of this patch outweigh the risk.
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