[alsa-devel] ASoC: atmel-pcm-dma: Leaking memory in atmel_pcm_hw_params

Bo Shen voice.shen at atmel.com
Tue Mar 19 02:18:43 CET 2013

Hi Lars,

On 3/18/2013 23:36, Lars-Peter Clausen wrote:
> On 03/18/2013 04:59 AM, Bo Shen wrote:
>> Hi Lars,
>> On 3/17/2013 22:39, Lars-Peter Clausen wrote:
>>> Hi,
>>> The dmaengine based pcm driver for atmel calls snd_dmaengine_pcm_open from
>>> it's hw_params callback. There is nothing preventing an application calling
>>> hw_params more than once. snd_dmaengine_pcm_open allocates a new prtd struct
>>> each time it gets called. So in case hw_params is called multiple times we
>>> leak memory here.
>> I use alsa utils and don't meet this issue. Please point out which software
>> you use meet this issue.
> I found the issue by looking at the code, but I think any application using
> the oss compatibility layer of ALSA will trigger this.

Thanks for this information.

>>> Is there any specific reason why snd_dmaengine_pcm_open() needs to be called
>>> from the hw_params callback and why it can't be called from the open
>>> callback?
>> This is because dma data setting and usage.
>> The filter function depends on the data returned by
>>> snd_soc_dai_get_dma_data(), but as far as I can see the DAI driver calls
>>> snd_soc_dai_set_dma_data() from its startup() callback, so the data is
>>> available in the PCM drivers open callback.
>> Have you test this yet?
> I don't have the hardware. I just looked at the code again, and it looks
> like I must have misread it the first time. snd_soc_dai_set_dma_data() is
> called from the DAI drivers hwparams callback. But the data that gets passed
> to snd_soc_dai_set_dma_data() doesn't really depend on anything that's only
> available in the hwparams callback. So the snd_soc_dai_set_dma_data() could
> easily be move to the DAI driver startup() callback.

I will implement this, and send patch for this.

Thanks again.

> - Lars

Best Regards,
Bo Shen

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