ASoC: dmaengine-pcm: Make requesting the DMA channel at PCM open optional

Refactor the dmaengine PCM library to allow the DMA channel to be requested
before opening a PCM substream. snd_dmaengine_pcm_open() now expects a DMA
channel instead of a filter function and filter parameter as its parameters.
snd_dmaengine_pcm_close() is updated to not release the DMA channel. This allows
a dmaengine based PCM driver to request its channels before the substream is
opened.

The patch also introduces two new functions, snd_dmaengine_pcm_open_request_chan()
and snd_dmaengine_pcm_close_release_chan(), which have the same signature and
behaviour of the old snd_dmaengine_pcm_{open,close}() and internally use the new
variants of these functions. All users of snd_dmaengine_pcm_{open,close}() are
updated to use snd_dmaengine_pcm_open_request_chan() and
snd_dmaengine_pcm_close_release_chan().

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Tested-by: Stephen Warren <swarren@nvidia.com>
Tested-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

sound/soc/omap/omap-pcm.c

@@ -118,8 +118,9 @@ static int omap_pcm_open(struct snd_pcm_substream *substream)
 
 	dma_data = snd_soc_dai_get_dma_data(rtd->cpu_dai, substream);
 
-	return snd_dmaengine_pcm_open(substream, omap_dma_filter_fn,
-				      dma_data->filter_data);
+	return snd_dmaengine_pcm_open_request_chan(substream,
+						   omap_dma_filter_fn,
+						   dma_data->filter_data);
 }
 
 static int omap_pcm_mmap(struct snd_pcm_substream *substream,
@@ -135,7 +136,7 @@ static int omap_pcm_mmap(struct snd_pcm_substream *substream,
 
 static struct snd_pcm_ops omap_pcm_ops = {
 	.open		= omap_pcm_open,
-	.close		= snd_dmaengine_pcm_close,
+	.close		= snd_dmaengine_pcm_close_release_chan,
 	.ioctl		= snd_pcm_lib_ioctl,
 	.hw_params	= omap_pcm_hw_params,
 	.hw_free	= omap_pcm_hw_free,