ASoC: soc.h: don't create dummy Component via COMP_DUMMY()

Many ASoC drivers define CPU/Codec/Platform dai_link by below macro.

	SND_SOC_DAILINK_DEFS(link,
(A)		     DAILINK_COMP_ARRAY(COMP_CPU("cpu_dai")),
(B)		     DAILINK_COMP_ARRAY(COMP_CODEC("codec", "dai1"),
(B)					COMP_CODEC("codec", "dai2")),
(C)		     DAILINK_COMP_ARRAY(COMP_EMPTY()));

In this case, this macro will be converted to like below

	[o] = static struct snd_soc_dai_link_component

(A)	[o] link_cpus[]      = {{ .dai_name = "cpu_dai" }};
(B)	[o] link_codecs[]    = {{ .dai_name = "dai1", .name = "codec" },
				{ .dai_name = "dai2", .name = "codec" }}
(C)	[o] link_platforms[] = {{ }};

CPU and Codec info will be filled by COMP_CPU() / COMP_CODEC (= A,B),
and Platform will have empty data by COMP_EMPTY() (= C) in this case.

Platform empty info will be filled when driver probe()
(most of case, CPU info will be copied to use soc-generic-dmaengine-pcm).

For example in case of DPCM FE/BE, it will be like below.
Codec will be dummy Component / DAI in this case (X).

	SND_SOC_DAILINK_DEFS(link,
		     DAILINK_COMP_ARRAY(COMP_CPU(...)),
(X)		     DAILINK_COMP_ARRAY(COMP_DUMMY()),
		     DAILINK_COMP_ARRAY(COMP_EMPTY()));

(X) part will converted like below

	[o] link_codecs[]    = {{ .name = "snd-soc-dummy",
				  .dai_name = "snd-soc-dummy-dai", }}

Even though we already have common asoc_dummy_dlc for dummy
Component / DAI, this macro will re-create new dummy dlc.
Some drivers defines many dai_link info via SND_SOC_DAILINK_DEFS(),
this means many dummy dlc also will be re-created. This is waste of
memory.

If we can use existing common asoc_dummy_dlc at (X),
we can avoid to re-creating dummy dlc, then, we can save the memory.

At that time, we want to keep existing code as much as possible, because
too many drivers are using this macro. But because of its original style,
using common asoc_dummy_dlc from it is very difficult or impossible.

So let's change the mind. The macro is used like below

	SND_SOC_DAILINK_DEFS(link,
		     DAILINK_COMP_ARRAY(COMP_CPU(...)),
(x)		     DAILINK_COMP_ARRAY(COMP_DUMMY()),
		     DAILINK_COMP_ARRAY(COMP_EMPTY()));

	static struct snd_soc_dai_link dai_links[] = {
	{
		.name = ...,
		.stream_name = ...,
(y)		SND_SOC_DAILINK_REG(link),
	},

(y) part will be like below

        static struct snd_soc_dai_link dai_links[] = {
        {
                .name = ...,
                .stream_name = ...,
 ^		...
 |		.codecs		= link_codecs,
(y)		.num_codecs	= ARRAY_SIZE(link_codecs),
 v		...
	}

This patch try to use trick on COMP_DUMMY()

-	#define COMP_DUMMY()	{ .name = "snd-soc-dummy", .dai_name = "snd-soc-dummy-dai", }
+	#define COMP_DUMMY()

By this tric, (x) part will be like below.

before
	[o] link_codecs[] = {{ .name = "snd-soc-dummy", .dai_name = "snd-soc-dummy-dai", }}
after
	[o] link_codecs[] = { };

This is same as below

	[o] link_codecs[0];

This means it has pointer (link_codecs), but the array size is 0.
(y) part will be like below.

	static struct snd_soc_dai_link dai_links[] = {
	{
		...
		.codecs		= link_codecs,
		.num_codecs	= 0,
		...
	},

This is very special settings that normal use usually not do,
but new macro do.
We can find this special settings on soc-core.c and fill it as
"dummy DAI" (= asoc_dummy_dlc). By this tric, we can avoid to re-create
dummy dlc and save the memory.

This patch add tric at COMP_DUMMY() and add snd_soc_fill_dummy_dai()
to fill dummy DAI.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://msgid.link/r/871qbi93qu.wl-kuninori.morimoto.gx@renesas.com


Signed-off-by: Mark Brown <broonie@kernel.org>