ASoC: rt711-sdca: add the notification when volume changed

This patch adds the return value when the volume settings were changed.
The userspace application might monitor the kcontrols to check which control changed.
Signed-off-by: Shuming Fan <shumingf@realtek.com>
Link: https://lore.kernel.org/r/20210422103235.22048-1-shumingf@realtek.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/codecs/rt711-sdca.c

@@ -509,12 +509,16 @@ static int rt711_sdca_set_gain_put(struct snd_kcontrol *kcontrol,
 		(struct soc_mixer_control *)kcontrol->private_value;
 	struct rt711_sdca_priv *rt711 = snd_soc_component_get_drvdata(component);
 	unsigned int read_l, read_r, gain_l_val, gain_r_val;
-	unsigned int i, adc_vol_flag = 0;
+	unsigned int i, adc_vol_flag = 0, changed = 0;
+	unsigned int lvalue, rvalue;
 
 	if (strstr(ucontrol->id.name, "FU1E Capture Volume") ||
 		strstr(ucontrol->id.name, "FU0F Capture Volume"))
 		adc_vol_flag = 1;
 
+	regmap_read(rt711->mbq_regmap, mc->reg, &lvalue);
+	regmap_read(rt711->mbq_regmap, mc->rreg, &rvalue);
+
 	/* control value to 2's complement value */
 	/* L Channel */
 	gain_l_val = ucontrol->value.integer.value[0];
@@ -560,6 +564,11 @@ static int rt711_sdca_set_gain_put(struct snd_kcontrol *kcontrol,
 		gain_r_val &= 0xffff;
 	}
 
+	if (lvalue != gain_l_val || rvalue != gain_r_val)
+		changed = 1;
+	else
+		return 0;
+
 	for (i = 0; i < 3; i++) { /* retry 3 times at most */
 		/* Lch*/
 		regmap_write(rt711->mbq_regmap, mc->reg, gain_l_val);
@@ -573,7 +582,7 @@ static int rt711_sdca_set_gain_put(struct snd_kcontrol *kcontrol,
 			break;
 	}
 
-	return i == 3 ? -EIO : 0;
+	return i == 3 ? -EIO : changed;
 }
 
 static int rt711_sdca_set_gain_get(struct snd_kcontrol *kcontrol,