linux-kernel - Re: [alsa-devel] [PATCH] ASoC: core: Use devm

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Date:	Thu, 16 Jan 2014 22:52:35 +0100
From:	Lars-Peter Clausen <lars@...afoo.de>
To:	Xiubo Li <Li.Xiubo@...escale.com>
CC:	lgirdwood@...il.com, broonie@...nel.org, perex@...ex.cz,
	tiwai@...e.de, alsa-devel@...a-project.org,
	linux-kernel@...r.kernel.org
Subject: Re: [alsa-devel] [PATCH] ASoC: core: Use devm_kzalloc() instead kzalloc()

On 01/16/2014 09:44 AM, Xiubo Li wrote:
> Makes the code slightly shorter
>
> Signed-off-by: Xiubo Li <Li.Xiubo@...escale.com>

I don't like this. I don't think it is a good design pattern to call devm 
function from within (especial non-devm) library functions. It creates an 
asymmetric API. The memory is allocated when snd_dmaengine_pcm_register() is 
called, but it is not freed when  snd_dmaengine_pcm_unregister() is called. 
This goes against the principle of least surprise.

- Lars

> ---
>   sound/soc/soc-generic-dmaengine-pcm.c | 4 +---
>   1 file changed, 1 insertion(+), 3 deletions(-)
>
> diff --git a/sound/soc/soc-generic-dmaengine-pcm.c b/sound/soc/soc-generic-dmaengine-pcm.c
> index 5bace12..bfb012f 100644
> --- a/sound/soc/soc-generic-dmaengine-pcm.c
> +++ b/sound/soc/soc-generic-dmaengine-pcm.c
> @@ -388,7 +388,7 @@ int snd_dmaengine_pcm_register(struct device *dev,
>   	struct dmaengine_pcm *pcm;
>   	int ret;
>
> -	pcm = kzalloc(sizeof(*pcm), GFP_KERNEL);
> +	pcm = devm_kzalloc(dev, sizeof(*pcm), GFP_KERNEL);
>   	if (!pcm)
>   		return -ENOMEM;
>
> @@ -408,7 +408,6 @@ int snd_dmaengine_pcm_register(struct device *dev,
>
>   err_free_dma:
>   	dmaengine_pcm_release_chan(pcm);
> -	kfree(pcm);
>   	return ret;
>   }
>   EXPORT_SYMBOL_GPL(snd_dmaengine_pcm_register);
> @@ -433,7 +432,6 @@ void snd_dmaengine_pcm_unregister(struct device *dev)
>
>   	snd_soc_remove_platform(platform);
>   	dmaengine_pcm_release_chan(pcm);
> -	kfree(pcm);
>   }
>   EXPORT_SYMBOL_GPL(snd_dmaengine_pcm_unregister);
>
>

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