[alsa-devel] About snd_dmaengine_pcm_trigger()

Lars-Peter Clausen lars at metafoo.de
Tue Mar 11 10:47:32 CET 2014

On 03/11/2014 05:47 AM, Kuninori Morimoto wrote:
> Hi Lars, Mark
>> Make them ASoC components ;) I don't know the hardware, but looking at the
>> code it doesn't seem to be that different from other modern host side audio
>> processing units. But one step at a time, first maybe try and see if you can
>> switch over to using the dmaengine PCM helper functions. Then later thing
>> about how this all can be better integrated into the ASoC framework.
> In my quick check,
> I guess, my drivers (FSI/rcar) can use
> ${LINUX}/sound/core/pcm_dmaengine.c methods as 1st step.
> OTOH, these drivers has PIO transfer too.
> So, if ALSA has PIO method like pcm_pio.c (?) which has similar method,
> it seems easy to switch over.
> But what do you think ?

If there are other platforms that also do PIO in a very similar way it might 
make sense to factor this out.

The reason why we factored out the dmaengine DMA stuff is because there is a 
standard API that hides the implementation details and is supposed to behave 
the same for each system. For PIO you do not have such a abstraction layer 
that hides the details, so I'm not sure how similar PIO between different 
platforms will actually be.

- Lars

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