linux-kernel - Re: [alsa-devel] [PATCH 2/5 v4] drm/i2c/adv7511: Add audio support

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Date:	Mon, 11 Apr 2016 11:33:47 +0200
From:	Lars-Peter Clausen <lars@...afoo.de>
To:	Jose Abreu <Jose.Abreu@...opsys.com>,
	linux-snps-arc@...ts.infradead.org, linux-kernel@...r.kernel.org,
	dri-devel@...ts.freedesktop.org, alsa-devel@...a-project.org
Cc:	architt@...eaurora.org, airlied@...ux.ie,
	Vineet.Gupta1@...opsys.com, Alexey.Brodkin@...opsys.com,
	lgirdwood@...il.com, CARLOS.PALMINHA@...opsys.com,
	broonie@...nel.org, tiwai@...e.com
Subject: Re: [alsa-devel] [PATCH 2/5 v4] drm/i2c/adv7511: Add audio support

On 04/11/2016 11:27 AM, Jose Abreu wrote:
> Hi Lars,
> 
> 
> On 09-04-2016 16:02, Lars-Peter Clausen wrote:
>> On 04/08/2016 06:12 PM, Jose Abreu wrote:
>> [...]
>>>> [...]
>>>>> +- adi,enable-audio: If set the ADV7511 driver will register a codec interface
>>>>> +  into ALSA SoC.
>>>> This is not a description of the hardware.
>>> Is this okay: "adi,enable-audio: Set this boolean parameter if ADV7511
>>> transmitter routes audio signals" ?
>> I don't think we need this property. There is no problem with registering
>> the audio part unconditionally. As long as there is no connection we wont
>> create a sound card that is exposed to userspace.
>>
> 
> This change was suggested by Laurent Pinchart and was introduced in v3. Quoting
> Laurent:
> "The idea is that enabling support for ADV7511 audio in the kernel isn't coupled
> with whether the system includes audio support. It would be confusing, and would
> also waste resources, to create a Linux sound device when no sound channel is
> routed on the board."

I wouldn't care too much about this at this point, the extra amount of
resources required for registering the CODEC (but not the sound card) is
just a few bytes (sizeof(struct snd_soc_codec)).

Nevertheless what we should do is describe the hardware and from this
information infer whether there is a audio connection or not and if there is
none we might skip registering the CODEC. In my opinion this hardware
description should be modeled using of-graph, having a connection between
the SoC side and the adv7511 SPDIF or I2S port.