ASoC: SOF: control: override volume info callback

ASoC dapm controls currently don't support more than 2 channels. This is
a problem for SOF-based devices where individual volume control cannot
be provided on the 4 DMIC input path.

If we want to provide controls for more than 2 channels, this patch
suggests a simple solution based on an override of the info callback.
For example, in the case with 4 channel DMIC PGAs, a sof_info callback
would be used. Mono and stereo cases will keep using the existing dapm
info callback.

A longer-term solution would be to remove the limits to 2 channels in
ASoC/DAPM/topology. This is a topic Intel is currently looking into,
e.g. by removing the use of 'reg' and 'rreg' fields and use arrays
instead. Such changes will be rather intrusive and touch multiple codec
and platform drivers. Removing restrictions is the right thing to do,
but this will need to be done in steps with lots of validation.
Signed-off-by: Jaska Uimonen <jaska.uimonen@linux.intel.com>
Reviewed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>
Link: https://lore.kernel.org/r/20201111173105.1927466-1-kai.vehmanen@linux.intel.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/sof/control.c

@@ -114,6 +114,28 @@ int snd_sof_volume_put(struct snd_kcontrol *kcontrol,
 	return change;
 }
 
+int snd_sof_volume_info(struct snd_kcontrol *kcontrol, struct snd_ctl_elem_info *uinfo)
+{
+	struct soc_mixer_control *sm = (struct soc_mixer_control *)kcontrol->private_value;
+	struct snd_sof_control *scontrol = sm->dobj.private;
+	unsigned int channels = scontrol->num_channels;
+	int platform_max;
+
+	if (!sm->platform_max)
+		sm->platform_max = sm->max;
+	platform_max = sm->platform_max;
+
+	if (platform_max == 1 && !strstr(kcontrol->id.name, " Volume"))
+		uinfo->type = SNDRV_CTL_ELEM_TYPE_BOOLEAN;
+	else
+		uinfo->type = SNDRV_CTL_ELEM_TYPE_INTEGER;
+
+	uinfo->count = channels;
+	uinfo->value.integer.min = 0;
+	uinfo->value.integer.max = platform_max - sm->min;
+	return 0;
+}
+
 int snd_sof_switch_get(struct snd_kcontrol *kcontrol,
 		       struct snd_ctl_elem_value *ucontrol)
 {

sound/soc/sof/sof-audio.h

@@ -124,6 +124,8 @@ int snd_sof_volume_get(struct snd_kcontrol *kcontrol,
 		       struct snd_ctl_elem_value *ucontrol);
 int snd_sof_volume_put(struct snd_kcontrol *kcontrol,
 		       struct snd_ctl_elem_value *ucontrol);
+int snd_sof_volume_info(struct snd_kcontrol *kcontrol,
+			struct snd_ctl_elem_info *ucontrol);
 int snd_sof_switch_get(struct snd_kcontrol *kcontrol,
 		       struct snd_ctl_elem_value *ucontrol);
 int snd_sof_switch_put(struct snd_kcontrol *kcontrol,

sound/soc/sof/topology.c

@@ -1041,6 +1041,15 @@ static int sof_control_load_volume(struct snd_soc_component *scomp,
 		goto out;
 	}
 
+	/*
+	 * If control has more than 2 channels we need to override the info. This is because even if
+	 * ASoC layer has defined topology's max channel count to SND_SOC_TPLG_MAX_CHAN = 8, the
+	 * pre-defined dapm control types (and related functions) creating the actual control
+	 * restrict the channels only to mono or stereo.
+	 */
+	if (le32_to_cpu(mc->num_channels) > 2)
+		kc->info = snd_sof_volume_info;
+
 	/* init the volume get/put data */
 	scontrol->size = struct_size(scontrol->control_data, chanv,
 				     le32_to_cpu(mc->num_channels));