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

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Date:	Mon, 11 Apr 2016 12:32:41 +0100
From:	Jose Abreu <Jose.Abreu@...opsys.com>
To:	Lars-Peter Clausen <lars@...afoo.de>,
	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

Hi Lars,


On 11-04-2016 10:33, Lars-Peter Clausen wrote:
> 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.
>

You mean something like this:

sound_playback: sound_playback {
    compatible = "simple-audio-card";
    [...]
    simple-audio-card,format = "i2s";
    [...]
}

adv7511@xx {
    compatible = "adi,adv7511";
    [...]

    ports {
        [...]
        /* Audio Output */
        port@x {
            reg = <x>;
            endpoint {
                remote-endpoint = <&sound_playback>;
            }
        }
    }
}

?

Best regards,
Jose Miguel Abreu