(Optional?) DMA vs. PIO

[Andy Shevchenko]

Hi!

During internal review of one patch I have been puzzled with the following code
and Pierre suggested to ask mailing list for help.

My main concern is what was the idea behind? Does it mean we support optional
DMA in such case? If now, why not to return an error code directly?

---8<---8<---8<---

> Why ASoC core has the following code in the first place:
> 
> 387              chan = dma_request_chan(dev, name);
> 388              if (IS_ERR(chan)) {
> 389                      if (PTR_ERR(chan) == -EPROBE_DEFER)
> 390                              return -EPROBE_DEFER;
> 391                      pcm->chan[i] = NULL;
> 392              } else {
> 393                      pcm->chan[i] = chan;
> 394              }
> 
> (note lines 389-391).
> If PIO fallback is not okay, why not to return an error there?

no idea, the code has been this way since 2013
(5eda87b890f867b098e5566b5543642851e8b9c3)

It's worth asking the question on the mailing list, I don't know if this is a
bug or a feature.

-- 
With Best Regards,
Andy Shevchenko