linux-kernel - Re: [alsa-devel] [PATCH 5/5 v4] ASoC: dwc: Update DOCUMENTATION for I2S Driver

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Date:	Fri, 8 Apr 2016 17:08:32 +0100
From:	Jose Abreu <Jose.Abreu@...opsys.com>
To:	Lars-Peter Clausen <lars@...afoo.de>,
	Jose Abreu <Jose.Abreu@...opsys.com>,
	Mark Brown <broonie@...nel.org>
CC:	<alsa-devel@...a-project.org>, <lgirdwood@...il.com>,
	<airlied@...ux.ie>, <Vineet.Gupta1@...opsys.com>,
	<Alexey.Brodkin@...opsys.com>, <linux-kernel@...r.kernel.org>,
	<dri-devel@...ts.freedesktop.org>, <CARLOS.PALMINHA@...opsys.com>,
	<tiwai@...e.com>, <linux-snps-arc@...ts.infradead.org>,
	<architt@...eaurora.org>
Subject: Re: [alsa-devel] [PATCH 5/5 v4] ASoC: dwc: Update DOCUMENTATION for
 I2S Driver

Hi Lars,


On 08-04-2016 16:52, Lars-Peter Clausen wrote:
> On 04/08/2016 12:06 PM, Jose Abreu wrote:
>> Hi Mark,
>>
>>
>> On 07-04-2016 18:53, Mark Brown wrote:
>>> On Thu, Apr 07, 2016 at 05:53:59PM +0100, Jose Abreu wrote:
>>>
>>>> + Optional properties:
>>>> + - snps,use-dmaengine: If set the driver will use ALSA DMA engine. If set
>>>> +   it is required to use the properties 'dmas' and 'dma-names'.
>>> This is not a good interface, it's describing Linux internal APIs.  If
>>> the device needs to operate in PIO mode it should just do that.
>> I added this interface because there is no direct way to check if DMA is
>> available on the I2S controller so it is not possible to automatically change
>> between DMA and PIO mode. As the I2S controller can be built with or without DMA
>> support it is necessary to somehow check if DMA is enabled or not and according
>> to that use either ALSA DMA engine or the custom platform driver sent in these
>> patches. I did not want to remove drivers functionality so I added this property
>> to the DT. This way a user can select between DMA and PIO mode.
> That's OK, but you need to describe the hardware, not the indented behavior
> of the software driver.
>

Is this okay: "snps,use-dmaengine: Set this boolean paramater if I2S controller
has DMA support. If set the properties 'dmas' and 'dma-names' must be also set" ?

Best regards,
Jose Miguel Abreu