Re: [PATCH v6 3/3] ASoC: Add multiple CPU DAI support in DAPM

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On 6/22/18 12:53 AM, Shreyas NC wrote:
On Thu, Jun 21, 2018 at 09:55:54PM -0500, Pierre-Louis Bossart wrote:


On 06/20/2018 05:54 AM, Shreyas NC wrote:
DAPM handles DAIs during soc_dapm_stream_event() and during addition
and creation of DAI widgets i.e., dapm_add_valid_dai_widget() and
dapm_connect_dai_link_widgets().
can you split this patch in two, one where you add
dapm_add_valid_dai_widget() and the second one where you add the multi-cpu
stuff? the current diff format is really hard to read with the two changes
lumped together.

As I had replied earlier, the change is really moving the same code from one
function to a new one. So, a patch split would mean we would have the same
duplicated code in one patch which surely is not desirable.

I don't understand your answer. It's fine to have a small preparation patch that just moves one piece of code to another function, and they change how that function is called.

I just realized that in my earlier reply I had excluded the list and replied
only to you :)


+	for (i = 0; i < rtd->num_codecs; i++) {
+		struct snd_soc_dai *codec_dai = rtd->codec_dais[i];
+
+		for (j = 0; j < rtd->num_cpu_dai; j++) {
+			cpu_dai = rtd->cpu_dais[j];
+
+			dapm_add_valid_dai_widget(card, rtd,
+						codec_dai, cpu_dai);

I didn't click on this earlier, but what makes you think all codec_dais are
connected to all cpu_dais?

Yes, there need not be a M:N connectivity. But, how do you find that out ?

That doesn't seem quite right.
For the multi-codec case, all the codec_dais hang from a single cpu_dai.
it's a stretch for me to have a full M:N connectivity. And that's clearly
not the case for SoundWire stream in the multi-link case.

I mostly do not disagree with you here..

Can't we use the dai_link information here to only connect cpu_ and
codec_dais that are related?

Which DAI Link information are you referring to here ?
Other than the machine driver which sets the audio route, I am unable to
figure out how we will find out the connected cpu_dai and codec_dais at
ASoC core level.

May be I am missing something :(

How is it different from the multi-codec support? You must have a description somewhere that tells you how the cpu_dai is connected to various codec_dais.

Maybe we should start with the examples you provided for Soundwire and describe how the dailinks would be represented.

With the M:N connectivity you'd end-up having spurious events with non-existent connections, it's not necessarily fatal but certainly not elegant and may or may not work depending on state management in codec drivers.


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