[PATCH 1/3] ASoC: bdw-rt5677: channel constraint support

[Brent Lu]

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@xxxxxxxxx>
---
 sound/soc/intel/boards/bdw-rt5677.c | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/sound/soc/intel/boards/bdw-rt5677.c b/sound/soc/intel/boards/bdw-rt5677.c
index cc41a34..7963cae 100644
--- a/sound/soc/intel/boards/bdw-rt5677.c
+++ b/sound/soc/intel/boards/bdw-rt5677.c
@@ -22,6 +22,8 @@
 
 #include "../../codecs/rt5677.h"
 
+#define DUAL_CHANNEL 2
+
 struct bdw_rt5677_priv {
 	struct gpio_desc *gpio_hp_en;
 	struct snd_soc_component *component;
@@ -222,6 +224,36 @@ static int bdw_rt5677_rtd_init(struct snd_soc_pcm_runtime *rtd)
 }
 #endif
 
+static const unsigned int channels[] = {
+	DUAL_CHANNEL,
+};
+
+static const struct snd_pcm_hw_constraint_list constraints_channels = {
+	.count = ARRAY_SIZE(channels),
+	.list = channels,
+	.mask = 0,
+};
+
+static int bdw_fe_startup(struct snd_pcm_substream *substream)
+{
+	struct snd_pcm_runtime *runtime = substream->runtime;
+
+	/*
+	 * On this platform for PCM device we support,
+	 * stereo audio
+	 */
+
+	runtime->hw.channels_max = DUAL_CHANNEL;
+	snd_pcm_hw_constraint_list(runtime, 0, SNDRV_PCM_HW_PARAM_CHANNELS,
+					   &constraints_channels);
+
+	return 0;
+}
+
+static const struct snd_soc_ops bdw_rt5677_fe_ops = {
+	.startup = bdw_fe_startup,
+};
+
 static int bdw_rt5677_init(struct snd_soc_pcm_runtime *rtd)
 {
 	struct bdw_rt5677_priv *bdw_rt5677 =
@@ -321,6 +353,7 @@ static struct snd_soc_dai_link bdw_rt5677_dais[] = {
 		},
 		.dpcm_capture = 1,
 		.dpcm_playback = 1,
+		.ops = &bdw_rt5677_fe_ops,
 		SND_SOC_DAILINK_REG(fe, dummy, platform),
 	},
 
-- 
2.7.4