[alsa-devel] multi-component: determine which DAI is active?

[Liam Girdwood]

On Wed, 2010-07-21 at 17:47 -0500, Timur Tabi wrote:
> Liam,
> 
> In order to get fsl_dma.c to work with the WM8776, which has separate DAIs
> for playback and capture, I've had to do this:
> 
> if (pcm->streams[0].substream) {
> 	ret = snd_dma_alloc_pages(SNDRV_DMA_TYPE_DEV, card->dev,
> 		fsl_dma_hardware.buffer_bytes_max,
> 		&pcm->streams[0].substream->dma_buffer);
> 	if (ret) {
> 		dev_err(card->dev, "can't allocate playback dma buffer\n");
> 		return ret;
> 	}
> }
> 
> if (pcm->streams[1].substream) {
> 	ret = snd_dma_alloc_pages(SNDRV_DMA_TYPE_DEV, card->dev,
> 		fsl_dma_hardware.buffer_bytes_max,
> 		&pcm->streams[1].substream->dma_buffer);
> 	if (ret) {
> 		snd_dma_free_pages(&pcm->streams[0].substream->dma_buffer);
> 		dev_err(card->dev, "can't allocate capture dma buffer\n");
> 		return ret;
> 	}
> }
> 
> That is, I need to check if the 'substream' pointer has been initialized.
> 
> This looks ugly to me.  In an earlier version of ASoC, I would have done this:
> 
> if (dai->playback.channels_min) {
> ...
> 
> if (dai->capture.channels_min) {
> ...
> 
> 
> But dai->playback and dai->capture no longer exist.  How should I handle this?
> 

Since the DAI driver max/min supported number of channels is driver
specific and static, it's now in the DAI driver :-

if (dai->driver->playback.channels_min) {

Liam

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