[PATCH v3 1/3] ASoC: soc-pcm: Indicate warning if dpcm_playback/capture were used for availability limition

[Kuninori Morimoto <kuninori.morimoto.gx@xxxxxxxxxxx>]

I have been wondering why DPCM needs special flag (= dpcm_playback/capture)
to use it. Below is the history why it was added to ASoC.

(A) In beginning, there was no dpcm_xxx flag on ASoC.
    It checks channels_min for DPCM, same as current non-DPCM.
    Let's name it as "validation check" here.

	if (rtd->dai_link->dynamic || rtd->dai_link->no_pcm) {
		if (cpu_dai->driver->playback.channels_min)
			playback = 1;
		if (cpu_dai->driver->capture.channels_min)
			capture = 1;

(B) commit 1e9de42f4324 ("ASoC: dpcm: Explicitly set BE DAI link supported
    stream directions") force to use dpcm_xxx flag on DPCM. According to
    this commit log, this is because "Some BE dummy DAI doesn't set
    channels_min for playback/capture". But we don't know which DAI is it,
    and not know why it can't/don't have channels_min. Let's name it as
    "no_chan_DAI" here. According to the code and git-log, it is used as
    DCPM-BE and is CPU DAI. I think the correct solution was set
    channels_min on "no_chan_DAI" side, not update ASoC framework side. But
    everything is under smoke today.

	if (rtd->dai_link->dynamic || rtd->dai_link->no_pcm) {
		playback = rtd->dai_link->dpcm_playback;
		capture  = rtd->dai_link->dpcm_capture;

(C) commit 9b5db059366a ("ASoC: soc-pcm: dpcm: Only allow playback/capture
    if supported") checks channels_min (= validation check) again. Because
    DPCM availability was handled by dpcm_xxx flag at that time, but some
    Sound Card set it even though it wasn't available. Clearly there's
    a contradiction here. I think correct solution was update Sound Card
    side instead of ASoC framework. Sound Card side will be updated to
    handle this issue later (commit 25612477d20b ("ASoC: soc-dai: set
    dai_link dpcm_ flags with a helper"))

	if (rtd->dai_link->dynamic || rtd->dai_link->no_pcm) {
		...
		playback = rtd->dai_link->dpcm_playback &&
			   snd_soc_dai_stream_valid(cpu_dai, ...);
		capture = rtd->dai_link->dpcm_capture &&
			   snd_soc_dai_stream_valid(cpu_dai, ...);

This (C) patch should have broken "no_chan_DAI" which doesn't have
channels_min, but there was no such report during this 4 years.
Possibilities case are as follows
	- No one is using "no_chan_DAI"
	- "no_chan_DAI" is no longer exist : was removed ?
	- "no_chan_DAI" is no longer exist : has channels_min ?

Because of these history, this dpcm_xxx is unneeded flag today. But because
we have been used it for 10 years since (B), it may have been used
differently. For example some DAI available both playback/capture, but it
set dpcm_playback flag only, in this case dpcm_xxx flag is used as
availability limitation. We can use playback_only flag instead in this
case, but it is very difficult to find such DAI today.

Let's add grace time to remove dpcm_playback/capture flag.

This patch don't use dpcm_xxx flag anymore, and indicates warning to use
xxx_only flag if both playback/capture were available but using only
one of dpcm_xxx flag, and not using xxx_only flag.

Link: https://lore.kernel.org/r/87edaym2cg.wl-kuninori.morimoto.gx@xxxxxxxxxxx
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@xxxxxxxxxxx>
Tested-by: Jerome Brunet <jbrunet@xxxxxxxxxxxx>
---
 include/sound/soc.h |  1 +
 sound/soc/soc-pcm.c | 65 ++++++++++++++++++++++++++-------------------
 2 files changed, 38 insertions(+), 28 deletions(-)

diff --git a/include/sound/soc.h b/include/sound/soc.h
index 33671437ee896..2a3da1d913776 100644
--- a/include/sound/soc.h
+++ b/include/sound/soc.h
@@ -815,6 +815,7 @@ struct snd_soc_dai_link {
 	/* This DAI link can route to other DAI links at runtime (Frontend)*/
 	unsigned int dynamic:1;
 
+	/* REMOVE ME */
 	/* DPCM capture and Playback support */
 	unsigned int dpcm_capture:1;
 	unsigned int dpcm_playback:1;
diff --git a/sound/soc/soc-pcm.c b/sound/soc/soc-pcm.c
index 711b2f49ed88d..c4d80cad59829 100644
--- a/sound/soc/soc-pcm.c
+++ b/sound/soc/soc-pcm.c
@@ -2795,6 +2795,7 @@ static int soc_get_playback_capture(struct snd_soc_pcm_runtime *rtd,
 {
 	struct snd_soc_dai_link *dai_link = rtd->dai_link;
 	struct snd_soc_dai *cpu_dai;
+	struct snd_soc_dai_link_ch_map *ch_maps;
 	int has_playback = 0;
 	int has_capture  = 0;
 	int i;
@@ -2805,43 +2806,51 @@ static int soc_get_playback_capture(struct snd_soc_pcm_runtime *rtd,
 	}
 
 	if (dai_link->dynamic || dai_link->no_pcm) {
-		int stream;
 
-		if (dai_link->dpcm_playback) {
-			stream = SNDRV_PCM_STREAM_PLAYBACK;
+		for_each_rtd_ch_maps(rtd, i, ch_maps) {
+			cpu_dai	  = snd_soc_rtd_to_cpu(rtd,   ch_maps->cpu);
 
-			for_each_rtd_cpu_dais(rtd, i, cpu_dai) {
-				if (snd_soc_dai_stream_valid(cpu_dai, stream)) {
-					has_playback = 1;
-					break;
-				}
-			}
-			if (!has_playback) {
-				dev_err(rtd->card->dev,
-					"No CPU DAIs support playback for stream %s\n",
-					dai_link->stream_name);
-				return -EINVAL;
-			}
+			if (snd_soc_dai_stream_valid(cpu_dai, SNDRV_PCM_STREAM_PLAYBACK))
+				has_playback = 1;
+
+			if (snd_soc_dai_stream_valid(cpu_dai, SNDRV_PCM_STREAM_CAPTURE))
+				has_capture = 1;
 		}
-		if (dai_link->dpcm_capture) {
-			stream = SNDRV_PCM_STREAM_CAPTURE;
 
-			for_each_rtd_cpu_dais(rtd, i, cpu_dai) {
-				if (snd_soc_dai_stream_valid(cpu_dai, stream)) {
-					has_capture = 1;
-					break;
-				}
+		/*
+		 * REMOVE ME
+		 *
+		 * dpcm_xxx flag will be removed soon, Indicates warning if dpcm_xxx flag was used
+		 * as availability limition
+		 */
+		if (has_playback && has_capture) {
+			if ( dai_link->dpcm_playback &&
+			    !dai_link->dpcm_capture  &&
+			    !dai_link->playback_only) {
+				dev_warn(rtd->card->dev,
+					 "both playback/capture are available,"
+					 " but not using playback_only flag (%s)\n",
+					 dai_link->stream_name);
+				dev_warn(rtd->card->dev,
+					 "dpcm_playback/capture are no longer needed,"
+					 " please use playback/capture_only instead\n");
+				has_capture = 0;
 			}
 
-			if (!has_capture) {
-				dev_err(rtd->card->dev,
-					"No CPU DAIs support capture for stream %s\n",
-					dai_link->stream_name);
-				return -EINVAL;
+			if (!dai_link->dpcm_playback &&
+			     dai_link->dpcm_capture  &&
+			    !dai_link->capture_only) {
+				dev_warn(rtd->card->dev,
+					 "both playback/capture are available,"
+					 " but not using capture_only flag (%s)\n",
+					 dai_link->stream_name);
+				dev_warn(rtd->card->dev,
+					 "dpcm_playback/capture are no longer needed,"
+					 " please use playback/capture_only instead\n");
+				has_playback = 0;
 			}
 		}
 	} else {
-		struct snd_soc_dai_link_ch_map *ch_maps;
 		struct snd_soc_dai *codec_dai;
 
 		/* Adapt stream for codec2codec links */
-- 
2.25.1