ASoC: ops: Don't modify the driver's plaform_max when reading state

Currently snd_soc_info_volsw() will set a platform_max based on the limit
the control has if one is not already set. This isn't really great, we
shouldn't be modifying the passed in driver data especially in a path like
this which may not ever be executed or where we may execute other callbacks
before this one. Instead make this function leave the data unchanged, and
clarify things a bit by referring to max rather than platform_max within
the function. platform_max is now applied as a limit after working out the
natural maximum value for the control.

This means that platform_max is no longer treated as a direct register
value for controls were min is non-zero. The put() callbacks already
validate on this basis, and there do not appear to be any in tree users
that would be affected.

Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20220603112508.3856519-1-broonie@kernel.org
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/soc-ops.c

@@ -176,20 +176,21 @@ int snd_soc_info_volsw(struct snd_kcontrol *kcontrol,
 {
 	struct soc_mixer_control *mc =
 		(struct soc_mixer_control *)kcontrol->private_value;
-	int platform_max;
+	int max;
 
-	if (!mc->platform_max)
-		mc->platform_max = mc->max;
-	platform_max = mc->platform_max;
+	max = uinfo->value.integer.max = mc->max - mc->min;
+	if (mc->platform_max && mc->platform_max < max)
+		max = mc->platform_max;
 
-	if (platform_max == 1 && !strstr(kcontrol->id.name, " Volume"))
+	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 = platform_max - mc->min;
+	uinfo->value.integer.max = max;
+
 	return 0;
 }
 EXPORT_SYMBOL_GPL(snd_soc_info_volsw);