ASoC: TWL4030: Add DAPM event handler for output MUX selection

DAPM event handler is set to filter out invalid MUX settings
for certain outputs.
Earpiece:
 - 0 = Off
 - 1 = DACL1
 - 2 = DACL2
 - 3 = *** Invalid ***
 - 4 = DACR1

PreDriveL/R:
 - 0 = Off/Off
 - 1 = DACL1/DACR1
 - 2 = DACL2/DACR2
 - 3 = *** Invalid/Invalid ***
 - 4 = DACR2/DACL2

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@nokia.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

sound/soc/codecs/twl4030.c

@@ -190,6 +190,30 @@ static void twl4030_init_chip(struct snd_soc_codec *codec)
 
 }
 
+static int outmixer_event(struct snd_soc_dapm_widget *w,
+	struct snd_kcontrol *kcontrol, int event)
+{
+	struct soc_enum *e = (struct soc_enum *)kcontrol->private_value;
+	int ret = 0;
+	int val;
+
+	switch (e->reg) {
+	case TWL4030_REG_PREDL_CTL:
+	case TWL4030_REG_PREDR_CTL:
+	case TWL4030_REG_EAR_CTL:
+		val = w->value >> e->shift_l;
+		if (val == 3) {
+			printk(KERN_WARNING
+			"Invalid MUX setting for register 0x%02x (%d)\n",
+			      e->reg, val);
+			ret = -1;
+		}
+		break;
+	}
+
+	return ret;
+}
+
 /*
  * Some of the gain controls in TWL (mostly those which are associated with
  * the outputs) are implemented in an interesting way: