[alsa-devel] [PATCH] ASoc: Handle multiple codecs with split playback / capture

[Ricard Wanderlof]

(Referring to this thread:
http://mailman.alsa-project.org/pipermail/alsa-devel/2015-June/093214.html)

This patch adds the capability to use multiple codecs on the same DAI 
link where one codec is used for playback and another one is used for 
capture.

As noted in the thread, there might be more places where the new 
snd_soc_dai_stream_valid() function is needed, however, these two were 
sufficient for our use case (SSM2518 playback and ICS-43432 capture).

Signed-off-by: Ricard Wanderlof <ricardw at xis.com>
---
 sound/soc/soc-pcm.c |   36 ++++++++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)

diff --git a/sound/soc/soc-pcm.c b/sound/soc/soc-pcm.c
index 6b0136e..df1f261 100644
--- a/sound/soc/soc-pcm.c
+++ b/sound/soc/soc-pcm.c
@@ -35,6 +35,32 @@
 #define DPCM_MAX_BE_USERS	8
 
 /**
+ * snd_soc_dai_stream_valid() - check if a DAI supports the given stream
+ *
+ * @dai: The DAI to check for stream support
+ * @stream: The stream type (playback / capture) to check for
+ *
+ * Checks if the DAI in question supports the indicated stream type.
+ * Needed to skip over codecs when iterating over
+ * snd_soc_pcm_runtime->codec_dais in order to skip codecs that are playback-
+ * or capture-only, which would otherwise inhibit capture or playback,
+ * respectively, to the other codec in a multiple codec / common I2S bus
+ * environment.
+ */
+static bool snd_soc_dai_stream_valid(struct snd_soc_dai *dai, int stream)
+{
+	struct snd_soc_pcm_stream *codec_stream;
+
+	if (stream == SNDRV_PCM_STREAM_PLAYBACK)
+		codec_stream = &dai->driver->playback;
+	else
+		codec_stream = &dai->driver->capture;
+
+	/* If the codec specifies any rate at all, it supports the stream. */
+	return !!codec_stream->rates;
+}
+
+/**
  * snd_soc_runtime_activate() - Increment active count for PCM runtime components
  * @rtd: ASoC PCM runtime that is activated
  * @stream: Direction of the PCM stream
@@ -371,6 +397,12 @@ static void soc_pcm_init_runtime_hw(struct snd_pcm_substream *substream)
 
 	/* first calculate min/max only for CODECs in the DAI link */
 	for (i = 0; i < rtd->num_codecs; i++) {
+
+		/* Skip codecs which don't support the current stream type. */
+		if (!snd_soc_dai_stream_valid(rtd->codec_dais[i],
+					      substream->stream))
+			continue;
+
 		codec_dai_drv = rtd->codec_dais[i]->driver;
 		if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
 			codec_stream = &codec_dai_drv->playback;
@@ -827,6 +859,10 @@ static int soc_pcm_hw_params(struct snd_pcm_substream *substream,
 		struct snd_soc_dai *codec_dai = rtd->codec_dais[i];
 		struct snd_pcm_hw_params codec_params;
 
+		/* Skip codecs which don't support the current stream type. */
+		if (!snd_soc_dai_stream_valid(codec_dai, substream->stream))
+			continue;
+
 		/* copy params for each codec */
 		codec_params = *params;
 
-- 
1.7.10.4

-- 
Ricard Wolf Wanderlöf                           ricardw(at)axis.com
Axis Communications AB, Lund, Sweden            www.axis.com
Phone +46 46 272 2016                           Fax +46 46 13 61 30