[PATCH v2 3/3] ASoC: broadwell: add channel constraint

[Brent Lu <brent.lu@intel.com>]

BDW boards using this machine driver supports only stereo capture and
playback. Implement a constraint to enforce it.

Signed-off-by: Brent Lu <brent.lu@intel.com>
---
 sound/soc/intel/boards/broadwell.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/sound/soc/intel/boards/broadwell.c b/sound/soc/intel/boards/broadwell.c
index f9a8336..07b2cfd 100644
--- a/sound/soc/intel/boards/broadwell.c
+++ b/sound/soc/intel/boards/broadwell.c
@@ -143,6 +143,31 @@ static int broadwell_rtd_init(struct snd_soc_pcm_runtime *rtd)
 }
 #endif
 
+static const unsigned int channels[] = {
+	2,
+};
+
+static const struct snd_pcm_hw_constraint_list constraints_channels = {
+	.count = ARRAY_SIZE(channels),
+	.list = channels,
+	.mask = 0,
+};
+
+static int broadwell_fe_startup(struct snd_pcm_substream *substream)
+{
+	struct snd_pcm_runtime *runtime = substream->runtime;
+
+	/* Board supports stereo configuration only */
+	runtime->hw.channels_max = 2;
+	return snd_pcm_hw_constraint_list(runtime, 0,
+					  SNDRV_PCM_HW_PARAM_CHANNELS,
+					  &constraints_channels);
+}
+
+static const struct snd_soc_ops broadwell_fe_ops = {
+	.startup = broadwell_fe_startup,
+};
+
 SND_SOC_DAILINK_DEF(system,
 	DAILINK_COMP_ARRAY(COMP_CPU("System Pin")));
 
@@ -180,6 +205,7 @@ static struct snd_soc_dai_link broadwell_rt286_dais[] = {
 		.init = broadwell_rtd_init,
 #endif
 		.trigger = {SND_SOC_DPCM_TRIGGER_POST, SND_SOC_DPCM_TRIGGER_POST},
+		.ops = &broadwell_fe_ops,
 		.dpcm_playback = 1,
 		.dpcm_capture = 1,
 		SND_SOC_DAILINK_REG(system, dummy, platform),
-- 
2.7.4