[PATCH] ASoC: dmaengine: Document support for TX only or RX only streams

[Andy Shevchenko]

On Thu, Oct 08, 2020 at 05:11:05PM +0100, Mark Brown wrote:
> We intentionally do not return an error if we get a permanent failure
> from dma_request_chan() in order to support systems which have TX only
> or RX only channels. Add a comment documenting this.

Thanks, makes sense!
Reviewed-by: Andy Shevchenko <andriy.shevchenko at intel.com>

> Reported-by: Andy Shevchenko <andriy.shevchenko at intel.com>
> Signed-off-by: Mark Brown <broonie at kernel.org>
> ---
>  sound/soc/soc-generic-dmaengine-pcm.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/sound/soc/soc-generic-dmaengine-pcm.c b/sound/soc/soc-generic-dmaengine-pcm.c
> index fb95c1464e66..9ef80a48707e 100644
> --- a/sound/soc/soc-generic-dmaengine-pcm.c
> +++ b/sound/soc/soc-generic-dmaengine-pcm.c
> @@ -386,6 +386,11 @@ static int dmaengine_pcm_request_chan_of(struct dmaengine_pcm *pcm,
>  			name = config->chan_names[i];
>  		chan = dma_request_chan(dev, name);
>  		if (IS_ERR(chan)) {
> +			/*
> +			 * Only report probe deferral errors, channels
> +			 * might not be present for devices that
> +			 * support only TX or only RX.
> +			 */
>  			if (PTR_ERR(chan) == -EPROBE_DEFER)
>  				return -EPROBE_DEFER;
>  			pcm->chan[i] = NULL;
> -- 
> 2.20.1
> 

-- 
With Best Regards,
Andy Shevchenko