ASoC: audio-graph: Identify 'no_pcm' DAI links for DPCM

PCM devices are created for FE dai links with 'no-pcm' flag as '0'.
Such DAI links have CPU component which implement either pcm_construct()
or pcm_new() at component or dai level respectively. Based on this,
current patch exposes a helper function to identify such components
and populate 'no_pcm' flag for DPCM DAI link.

This helps to have BE<->BE component links where PCM devices need
not be created for CPU component involved in such links.
Signed-off-by: Sameer Pujar <spujar@nvidia.com>
Cc: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://lore.kernel.org/r/1604329814-24779-5-git-send-email-spujar@nvidia.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/generic/audio-graph-card.c

@@ -111,6 +111,17 @@ static int graph_get_dai_id(struct device_node *ep)
 	return id;
 }
 
+static bool soc_component_is_pcm(struct snd_soc_dai_link_component *dlc)
+{
+	struct snd_soc_dai *dai = snd_soc_find_dai_with_mutex(dlc);
+
+	if (dai && (dai->component->driver->pcm_construct ||
+		    dai->driver->pcm_new))
+		return true;
+
+	return false;
+}
+
 static int asoc_simple_parse_dai(struct device_node *ep,
 				 struct snd_soc_dai_link_component *dlc,
 				 int *is_single_link)
@@ -205,6 +216,7 @@ static int graph_dai_link_of_dpcm(struct asoc_simple_priv *priv,
 				  int dup_codec)
 {
 	struct device *dev = simple_priv_to_dev(priv);
+	struct snd_soc_card *card = simple_priv_to_card(priv);
 	struct snd_soc_dai_link *dai_link = simple_priv_to_link(priv, li->link);
 	struct simple_dai_props *dai_props = simple_priv_to_props(priv, li->link);
 	struct device_node *top = dev->of_node;
@@ -259,6 +271,19 @@ static int graph_dai_link_of_dpcm(struct asoc_simple_priv *priv,
 		if (ret < 0)
 			goto out_put_node;
 
+		/*
+		 * In BE<->BE connections it is not required to create
+		 * PCM devices at CPU end of the dai link and thus 'no_pcm'
+		 * flag needs to be set. It is useful when there are many
+		 * BE components and some of these have to be connected to
+		 * form a valid audio path.
+		 *
+		 * For example: FE <-> BE1 <-> BE2 <-> ... <-> BEn where
+		 * there are 'n' BE components in the path.
+		 */
+		if (card->component_chaining && !soc_component_is_pcm(cpus))
+			dai_link->no_pcm = 1;
+
 		/* card->num_links includes Codec */
 		asoc_simple_canonicalize_cpu(dai_link, is_single_links);
 	} else {