ASoC: macaudio: Add 'Speakers Up Indicator' control

This control is there for userspace convenience, so that daemons
watching I/V sense data know when to open the sense PCM. If they open
the PCM without playback in progress, there will be no clocks on the
bus and the sense capture PCM will be stuck.

Signed-off-by: Martin Povišer <povik+lin@cutebit.org>

Author: povik

sound/soc/apple/macaudio.c

@@ -73,6 +73,9 @@ struct macaudio_snd_data {
 		bool is_headphones;
 		unsigned int tdm_mask;
 	} *link_props;
+
+	bool speakers_streaming;
+	struct snd_kcontrol *speakers_streaming_kctl;
 };
 
 static bool please_blow_up_my_speakers;
@@ -566,13 +569,45 @@ static void macaudio_dpcm_shutdown(struct snd_pcm_substream *substream)
 	}
 }
 
+static int macaudio_be_prepare(struct snd_pcm_substream *substream)
+{
+	struct snd_soc_pcm_runtime *rtd = snd_soc_substream_to_rtd(substream);
+	struct macaudio_snd_data *ma = snd_soc_card_get_drvdata(rtd->card);
+	struct macaudio_link_props *props = &ma->link_props[rtd->dai_link->id];
+
+	if (props->is_speakers) {
+		ma->speakers_streaming = true;
+		snd_ctl_notify(ma->card.snd_card, SNDRV_CTL_EVENT_MASK_VALUE,
+			       &ma->speakers_streaming_kctl->id);
+	}
+
+	return 0;
+}
+
+static int macaudio_be_hw_free(struct snd_pcm_substream *substream)
+{
+	struct snd_soc_pcm_runtime *rtd = snd_soc_substream_to_rtd(substream);
+	struct macaudio_snd_data *ma = snd_soc_card_get_drvdata(rtd->card);
+	struct macaudio_link_props *props = &ma->link_props[rtd->dai_link->id];
+
+	if (props->is_speakers) {
+		ma->speakers_streaming = false;
+		snd_ctl_notify(ma->card.snd_card, SNDRV_CTL_EVENT_MASK_VALUE,
+			       &ma->speakers_streaming_kctl->id);
+	}
+
+	return 0;
+}
+
 static const struct snd_soc_ops macaudio_fe_ops = {
 	.startup	= macaudio_fe_startup,
 	.shutdown	= macaudio_dpcm_shutdown,
 	.hw_params	= macaudio_fe_hw_params,
 };
 
 static const struct snd_soc_ops macaudio_be_ops = {
+	.prepare	= macaudio_be_prepare,
+	.hw_free	= macaudio_be_hw_free,
 	.shutdown	= macaudio_dpcm_shutdown,
 	.hw_params	= macaudio_dpcm_hw_params,
 };
@@ -803,6 +838,8 @@ static int macaudio_late_probe(struct snd_soc_card *card)
 		}
 	}
 
+	ma->speakers_streaming_kctl = snd_soc_card_get_kcontrol(card, "Speakers Up Indicator");
+
 	return 0;
 }
 
@@ -976,10 +1013,42 @@ static const struct snd_soc_dapm_widget macaudio_snd_widgets[] = {
 	SND_SOC_DAPM_AIF_IN("Speaker Sense Capture", NULL, 0, SND_SOC_NOPM, 0, 0),
 };
 
+static int macaudio_sss_info(struct snd_kcontrol *kcontrol, struct snd_ctl_elem_info *uinfo)
+{
+	uinfo->type = SNDRV_CTL_ELEM_TYPE_BOOLEAN;
+	uinfo->count = 1;
+	uinfo->value.integer.min = 0;
+	uinfo->value.integer.max = 1;
+
+	return 0;
+}
+
+static int macaudio_sss_get(struct snd_kcontrol *kcontrol, struct snd_ctl_elem_value *uvalue)
+{
+	struct snd_soc_card *card = snd_kcontrol_chip(kcontrol);
+	struct macaudio_snd_data *ma = snd_soc_card_get_drvdata(card);
+
+	/*
+	 * TODO: Check if any locking is in order here. I would
+	 * assume there is some ALSA-level lock, but DAPM implementations
+	 * of kcontrol ops do explicit locking, so look into it.
+	 */
+	uvalue->value.integer.value[0] = ma->speakers_streaming;
+
+	return 0;
+}
+
 static const struct snd_kcontrol_new macaudio_controls[] = {
 	SOC_DAPM_PIN_SWITCH("Speaker"),
 	SOC_DAPM_PIN_SWITCH("Headphone"),
 	SOC_DAPM_PIN_SWITCH("Headset Mic"),
+	{
+		.iface = SNDRV_CTL_ELEM_IFACE_MIXER,
+		.access = SNDRV_CTL_ELEM_ACCESS_READ |
+			SNDRV_CTL_ELEM_ACCESS_VOLATILE,
+		.name = "Speakers Up Indicator",
+		.info = macaudio_sss_info, .get = macaudio_sss_get,
+	},
 };
 
 static const struct snd_soc_dapm_route macaudio_dapm_routes[] = {