ASoC: ops: Clarify snd_soc_info_volsw_sx()

Currently snd_soc_info_volsw_sx() is implemented indirectly, wrapping
snd_soc_info_volsw() and modifying the values it sets up rather than
directly setting up the values reported to userspace. This makes it much
harder to follow what the intended behaviour of these controls is. Let's
rewrite the function to be self contained with a clarifying comment at the
top in an effort to help maintainability.
Signed-off-by: Mark Brown <broonie@kernel.org>
Reviewed-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Tested-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Link: https://lore.kernel.org/r/20220602092921.3302713-1-broonie@kernel.orgSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/soc-ops.c

@@ -203,7 +203,8 @@ EXPORT_SYMBOL_GPL(snd_soc_info_volsw);
  * Callback to provide information about a single mixer control, or a double
  * mixer control that spans 2 registers of the SX TLV type. SX TLV controls
  * have a range that represents both positive and negative values either side
- * of zero but without a sign bit.
+ * of zero but without a sign bit. min is the minimum register value, max is
+ * the number of steps.
  *
  * Returns 0 for success.
  */
@@ -212,12 +213,21 @@ int snd_soc_info_volsw_sx(struct snd_kcontrol *kcontrol,
 {
 	struct soc_mixer_control *mc =
 		(struct soc_mixer_control *)kcontrol->private_value;
+	int max;
 
-	snd_soc_info_volsw(kcontrol, uinfo);
-	/* Max represents the number of levels in an SX control not the
-	 * maximum value, so add the minimum value back on
-	 */
-	uinfo->value.integer.max += mc->min;
+	if (mc->platform_max)
+		max = mc->platform_max;
+	else
+		max = mc->max;
+
+	if (max == 1 && !strstr(kcontrol->id.name, " Volume"))
+		uinfo->type = SNDRV_CTL_ELEM_TYPE_BOOLEAN;
+	else
+		uinfo->type = SNDRV_CTL_ELEM_TYPE_INTEGER;
+
+	uinfo->count = snd_soc_volsw_is_stereo(mc) ? 2 : 1;
+	uinfo->value.integer.min = 0;
+	uinfo->value.integer.max = max;
 
 	return 0;
 }