[PATCH v4 28/32] sound: soc: qdsp6: Add SND kcontrol for fetching offload status

[Wesley Cheng]

Add a kcontrol to the platform sound card to fetch the current offload
status.  This can allow for userspace to ensure/check which USB SND
resources are actually busy versus having to attempt opening the USB SND
devices, which will result in an error if offloading is active.

Signed-off-by: Wesley Cheng <quic_wcheng at quicinc.com>
---
 sound/soc/qcom/qdsp6/q6usb.c | 104 ++++++++++++++++++++++++++++++++++-
 1 file changed, 101 insertions(+), 3 deletions(-)

diff --git a/sound/soc/qcom/qdsp6/q6usb.c b/sound/soc/qcom/qdsp6/q6usb.c
index 87e88dafd8ad..e4ccb9d912b0 100644
--- a/sound/soc/qcom/qdsp6/q6usb.c
+++ b/sound/soc/qcom/qdsp6/q6usb.c
@@ -30,6 +30,8 @@ struct q6usb_status {
 	unsigned int num_pcm;
 	unsigned int chip_index;
 	unsigned int pcm_index;
+	bool prepared;
+	bool running;
 };
 
 struct q6usb_port_data {
@@ -52,6 +54,17 @@ static const struct snd_soc_dapm_route q6usb_dapm_routes[] = {
 	{"USB Playback", NULL, "USB_RX_BE"},
 };
 
+static int q6usb_find_running(struct q6usb_port_data *data)
+{
+	int i;
+
+	for (i = 0; i < SNDRV_CARDS; i++) {
+		if (data->status[i].running)
+			return i;
+	}
+	return -ENODEV;
+}
+
 static int q6usb_hw_params(struct snd_pcm_substream *substream,
 			   struct snd_pcm_hw_params *params,
 			   struct snd_soc_dai *dai)
@@ -81,14 +94,40 @@ static int q6usb_hw_params(struct snd_pcm_substream *substream,
 		goto out;
 
 	data->status[data->sel_card_idx].pcm_index = data->sel_pcm_idx;
+	data->status[data->sel_card_idx].prepared = true;
 out:
 	mutex_unlock(&data->mutex);
 
 	return ret;
 }
 
+static int q6usb_prepare(struct snd_pcm_substream *substream,
+		struct snd_soc_dai *dai)
+{
+	struct q6usb_port_data *data = dev_get_drvdata(dai->dev);
+
+	mutex_lock(&data->mutex);
+	data->status[data->sel_card_idx].running = true;
+	mutex_unlock(&data->mutex);
+
+	return 0;
+}
+
+static void q6usb_shutdown(struct snd_pcm_substream *substream,
+				struct snd_soc_dai *dai)
+{
+	struct q6usb_port_data *data = dev_get_drvdata(dai->dev);
+
+	mutex_lock(&data->mutex);
+	data->status[data->sel_card_idx].running = false;
+	data->status[data->sel_card_idx].prepared = false;
+	mutex_unlock(&data->mutex);
+}
+
 static const struct snd_soc_dai_ops q6usb_ops = {
 	.hw_params = q6usb_hw_params,
+	.prepare = q6usb_prepare,
+	.shutdown = q6usb_shutdown,
 };
 
 static struct snd_soc_dai_driver q6usb_be_dais[] = {
@@ -148,10 +187,15 @@ static int q6usb_put_offload_dev(struct snd_kcontrol *kcontrol,
 	int pcmidx;
 	int cardidx;
 
+	mutex_lock(&data->mutex);
+
+	/* Don't allow changes to the offloading devices if session is busy */
+	if (data->sel_card_idx >= 0 && data->status[data->sel_card_idx].prepared)
+		goto out;
+
 	cardidx = ucontrol->value.integer.value[0];
 	pcmidx = ucontrol->value.integer.value[1];
 
-	mutex_lock(&data->mutex);
 	if ((cardidx >= 0 && test_bit(cardidx, &data->available_card_slot))) {
 		data->sel_card_idx = cardidx;
 		changed = 1;
@@ -162,6 +206,8 @@ static int q6usb_put_offload_dev(struct snd_kcontrol *kcontrol,
 		data->idx_valid = true;
 		changed = 1;
 	}
+
+out:
 	mutex_unlock(&data->mutex);
 
 	return changed;
@@ -187,11 +233,59 @@ static const struct snd_kcontrol_new q6usb_offload_dev_ctrl = {
 	.put = q6usb_put_offload_dev,
 };
 
+static int q6usb_mixer_get_offload_status(struct snd_kcontrol *kcontrol,
+				   struct snd_ctl_elem_value *ucontrol)
+{
+	struct snd_soc_component *component = snd_kcontrol_chip(kcontrol);
+	struct q6usb_port_data *data = dev_get_drvdata(component->dev);
+	int running;
+	int card_idx;
+	int pcm_idx;
+
+	running = q6usb_find_running(data);
+	if (running < 0) {
+		card_idx = -1;
+		pcm_idx = -1;
+	} else {
+		card_idx = running;
+		pcm_idx = data->status[running].pcm_index;
+	}
+
+	ucontrol->value.integer.value[0] = card_idx;
+	ucontrol->value.integer.value[1] = pcm_idx;
+	return 0;
+}
+
+static int q6usb_offload_ctl_info(struct snd_kcontrol *kcontrol,
+			      struct snd_ctl_elem_info *uinfo)
+{
+	uinfo->type = SNDRV_CTL_ELEM_TYPE_INTEGER;
+	uinfo->count = 2;
+	uinfo->value.integer.min = 0;
+	uinfo->value.integer.max = SNDRV_CARDS;
+
+	return 0;
+}
+
+static const struct snd_kcontrol_new q6usb_offload_control = {
+	.iface = SNDRV_CTL_ELEM_IFACE_CARD,
+	.access = SNDRV_CTL_ELEM_ACCESS_READ,
+	.name = "Q6USB offload status",
+	.info = q6usb_offload_ctl_info,
+	.get = q6usb_mixer_get_offload_status,
+	.put = NULL,
+};
+
 /* Build a mixer control for a UAC connector control (jack-detect) */
 static void q6usb_connector_control_init(struct snd_soc_component *component)
 {
 	int ret;
 
+	ret = snd_ctl_add(component->card->snd_card,
+				snd_ctl_new1(&q6usb_offload_control, component));
+	if (ret < 0)
+		return;
+
 	ret = snd_ctl_add(component->card->snd_card,
 				snd_ctl_new1(&q6usb_offload_dev_ctrl, component));
 	if (ret < 0)
@@ -229,8 +323,12 @@ static int q6usb_alsa_connection_cb(struct snd_soc_usb *usb, int card_idx,
 	mutex_lock(&data->mutex);
 	if (connected) {
 		snd_soc_dapm_enable_pin(dapm, "USB_RX_BE");
-		/* We only track the latest USB headset plugged in */
-		if (!data->idx_valid || data->sel_card_idx < 0)
+		/*
+		 * Update the latest USB headset plugged in, if session is
+		 * idle.
+		 */
+		if ((!data->idx_valid || data->sel_card_idx < 0) &&
+			!data->status[data->sel_card_idx].prepared)
 			data->sel_card_idx = card_idx;
 
 		set_bit(card_idx, &data->available_card_slot);