[alsa-devel] [PATCH v4 08/13] ASoC: Add SoundWire stream programming interface

[Pierre-Louis Bossart]

On 4/24/18 9:49 PM, Vinod Koul wrote:
> On Tue, Apr 24, 2018 at 06:40:54PM -0500, Pierre-Louis Bossart wrote:
>> On 4/24/18 4:06 AM, Vinod Koul wrote:
>>> On Mon, Apr 23, 2018 at 08:33:08AM -0500, Pierre-Louis Bossart wrote:
>>>> On 4/21/18 10:58 AM, Vinod Koul wrote:
>>>>> On Sat, Apr 21, 2018 at 06:59:49AM -0700, Pierre-Louis Bossart wrote:
>>>>>>
>>>>>>> +/**
>>>>>>> + * snd_soc_dai_set_sdw_stream() - Configures a DAI for SDW stream operation
>>>>>>> + * @dai: DAI
>>>>>>> + * @stream: STREAM
>>>>>>> + * @direction: Stream direction(Playback/Capture)
>>>>>>> + * SoundWire subsystem doesn't have a notion of direction and we reuse
>>>>>>> + * the ASoC stream direction to configure sink/source ports.
>>>>>>> + * Playback maps to source on the TX and sink on Rx. Vice-versa for Capture.
>>>>>>
>>>>>> this is just confusing...
>>>>>>
>>>>>> This should be something like
>>>>>> "use Playback for source ports and Capture for sink ports".
>>>>>
>>>>> Source port on ...? This is also confusing to me!
>>>>>
>>>>> For playback there are two ports, one on transmitter aka
>>>>> TX and one on receiver aka RX. For Tx we use source port, and Rx uses sink
>>>>> ports. I should probably add port to make people really figure out we are
>>>>> talking about ports!
>>>>>
>>>>> So:
>>>>>
>>>>> Playback maps to source port on the TX and sink port on Rx. Vice-versa for Capture.
>>>>>
>>>>> Do you agree to above statement?
>>>>
>>>> No. Source port and TX are redundant definitions, and your wording isn't
>>>> clear: is the PLAYBACK/CAPTURE qualifier for the stream or the DAI used by
>>>> the stream?
>>>
>>> Yes they are redundant, will update. PLAYBACK/CAPTURE qualifier is for stream.
>>
>> Let me try again.
>> let's say in point-to-point mode you have dai1 as the source and dai2 as the
>> sink.
>>
>> Which sequence are the higher layers supposed to use:
>>
>> a.
>>
>> snd_soc_dai_set_sdw_stream(dai1, stream, PLAYBACK);
>> snd_soc_dai_set_sdw_stream(dai2, stream, PLAYBACK);
>>
>> b.
>>
>> snd_soc_dai_set_sdw_stream(dai1, stream, PLAYBACK);
>> snd_soc_dai_set_sdw_stream(dai2, stream, CAPTURE);
> 
> I believe this.

For clarity, did you mean b) ?
If yes, Playback == Source and Capture == sink.