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

From: Mark Brown <broonie@kernel.org>
To: Andy Shevchenko <andriy.shevchenko@intel.com>
Cc: alsa-devel@alsa-project.org, Lars-Peter Clausen <lars@metafoo.de>,
	Stephen Warren <swarren@nvidia.com>,
	Liam Girdwood <lgirdwood@gmail.com>,
	Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>,
	Michael Wei Hong Sit <michael.wei.hong.sit@intel.com>
Subject: Re: [PATCH] ASoC: dmaengine: Document support for TX only or RX only streams
Date: Mon, 12 Oct 2020 16:48:03 +0100	[thread overview]
Message-ID: <20201012154803.GG4332@sirena.org.uk> (raw)
In-Reply-To: <20201012135527.GW4077@smile.fi.intel.com>

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On Mon, Oct 12, 2020 at 04:55:27PM +0300, Andy Shevchenko wrote:

> Currently those drivers need to do something like:

> 	if (of_property_is_present("dma-names"))
> 		ret = try DMA mode;
> 	else
> 		ret = try PIO mode;

> but this seems to me a bit stricter than needed. What if DMA mode fails, shall
> we fail the probe of the driver?

They can also just try registering DMA and fall back to PIO.

> If ASoC supports optional DMA resources, above can be simplified to something
> like:

> 	ret = try DMA mode;
> 	if (ret != DMA mode ok)
> 		ret = try PIO mode;

> which makes OF dependent parts gone along with relying on the properties rather
> than real resource availability.

I don't understand the blocker to writing that code at the minute?

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