[alsa-devel] [PATCH 0/2] ASoC: dmaengine_pcm: support generic DMA binding users

Mark Brown broonie at opensource.wolfsonmicro.com
Thu Mar 21 16:22:06 CET 2013

On Thu, Mar 21, 2013 at 04:06:27PM +0100, Lars-Peter Clausen wrote:

> Hm, I only saw this series today would have been good to be on Cc. I've been
> working on something very similar. My series goes a bit further though, it
> implements an (almost generic) dmaengine based PCM driver using the of
> bindings. So you need almost no platform code. The only things that are
> platform specific at the moment is the pcm_hardware struct, but I'd like to
> replace that in the future with something that queries the pcm hardware
> parameter like max_period from the DMA engine driver. And another bit that is
> still driver specific is a callback that fills the dma_slave_config struct.

FWIW it might be worth looking at the one rmk wrote but has never wanted
to submit for whatever reason.

> In my series the channels are requested at probe time, so it is possible to
> handle -EPROBE_DEFER properly and also we can allocate the audio buffers with
> the dma device instead of the sound device, so stupid hacks like

>     card->dev->dma_mask = &dma_mask;
>     card->dev->coherent_dma_mask = DMA_BIT_MASK(32);

> anymore. I'll try to post the series tomorrow.

This is the main thing his code has got that the library hasn't, it's
certainly the only issue he keeps mentioning.
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