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

From: Jose Abreu <Jose.Abreu@synopsys.com>
To: Lars-Peter Clausen <lars@metafoo.de>,
	Jose Abreu <Jose.Abreu@synopsys.com>,
	Mark Brown <broonie@kernel.org>
Cc: <alsa-devel@alsa-project.org>, <Vineet.Gupta1@synopsys.com>,
	<Alexey.Brodkin@synopsys.com>, <lgirdwood@gmail.com>,
	<dri-devel@lists.freedesktop.org>, <linux-kernel@vger.kernel.org>,
	<CARLOS.PALMINHA@synopsys.com>, <tiwai@suse.com>,
	<linux-snps-arc@lists.infradead.org>
Subject: Re: [alsa-devel] [PATCH 5/5 v4] ASoC: dwc: Update DOCUMENTATION for I2S Driver
Date: Mon, 11 Apr 2016 10:24:54 +0100	[thread overview]
Message-ID: <570B6D66.4080309@synopsys.com> (raw)
In-Reply-To: <570917E9.8020804@metafoo.de>

Hi Lars,

On 09-04-2016 15:55, Lars-Peter Clausen wrote:
> On 04/08/2016 06:08 PM, Jose Abreu wrote:
>> 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" ?
> The description is better. But the name of the property is still imperative
> rather then descriptive. It tells the software what should be done rather
> then describing what the hardware looks like.
>
> Since there is already the dmas property which is present if a DMA is
> connected and is absent when no DMA is present it should be enough to just
> check that property rather than requiring an additional one.

Ok, will then use the DMA property to decide which mode to use: PIO or DMA.

>
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Best regards,
Jose Miguel Abreu