[PATCH v10 31/41] ASoC: Add SND kcontrol for fetching USB offload status

[Wesley Cheng <quic_wcheng@quicinc.com>]

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@quicinc.com>
---
 include/sound/soc-usb.h |  27 ++++++++
 sound/soc/soc-usb.c     | 150 +++++++++++++++++++++++++++++++++++++++-
 2 files changed, 175 insertions(+), 2 deletions(-)

diff --git a/include/sound/soc-usb.h b/include/sound/soc-usb.h
index 195300510acc..b0dbb89316fe 100644
--- a/include/sound/soc-usb.h
+++ b/include/sound/soc-usb.h
@@ -6,6 +6,24 @@
 #ifndef __LINUX_SND_SOC_USB_H
 #define __LINUX_SND_SOC_USB_H
 
+enum snd_soc_usb_dai_state {
+	SND_SOC_USB_IDLE,
+	SND_SOC_USB_PREPARED,
+	SND_SOC_USB_RUNNING,
+};
+
+/**
+ * struct snd_soc_usb_session
+ * @active_card_idx - active offloaded sound card
+ * @active_pcm_idx - active offloaded PCM device
+ * @state - USB BE DAI link PCM state
+ */
+struct snd_soc_usb_session {
+	int active_card_idx;
+	int active_pcm_idx;
+	enum snd_soc_usb_dai_state state;
+};
+
 /**
  * struct snd_soc_usb_device
  * @card_idx - sound card index associated with USB device
@@ -25,6 +43,8 @@ struct snd_soc_usb_device {
  * @list - list head for SND SOC struct list
  * @dev - USB backend device reference
  * @component - reference to ASoC component
+ * @active_list - active sessions
+ * @num_supported_streams - number of supported concurrent sessions
  * @connection_status_cb - callback to notify connection events
  * @put_offload_dev - callback to select USB sound card/PCM device
  * @get_offload_dev - callback to fetch selected USB sound card/PCM device
@@ -33,6 +53,8 @@ struct snd_soc_usb_device {
 struct snd_soc_usb {
 	struct list_head list;
 	struct snd_soc_component *component;
+	struct snd_soc_usb_session *active_list;
+	unsigned int num_supported_streams;
 	int (*connection_status_cb)(struct snd_soc_usb *usb,
 			struct snd_soc_usb_device *sdev, bool connected);
 	int (*put_offload_dev)(struct snd_kcontrol *kcontrol,
@@ -50,6 +72,11 @@ int snd_soc_usb_connect(struct device *usbdev, struct snd_soc_usb_device *sdev);
 int snd_soc_usb_disconnect(struct device *usbdev, struct snd_soc_usb_device *sdev);
 void *snd_soc_usb_find_priv_data(struct device *dev);
 
+int snd_soc_usb_prepare_session(struct snd_soc_usb *usb, int card_idx, int pcm_idx);
+int snd_soc_usb_shutdown_session(struct snd_soc_usb *usb, int session_id);
+int snd_soc_usb_set_session_state(struct snd_soc_usb *usb, int session_id,
+				  enum snd_soc_usb_dai_state state);
+
 struct snd_soc_usb *snd_soc_usb_allocate_port(struct snd_soc_component *component,
 			int num_supported_streams, void *data);
 void snd_soc_usb_free_port(struct snd_soc_usb *usb);
diff --git a/sound/soc/soc-usb.c b/sound/soc/soc-usb.c
index 622916a82b77..50cd53db365f 100644
--- a/sound/soc/soc-usb.c
+++ b/sound/soc/soc-usb.c
@@ -42,11 +42,62 @@ static struct snd_soc_usb *snd_soc_find_usb_ctx(struct device_node *node)
 }
 
 /* SOC USB sound kcontrols */
+static int snd_soc_usb_get_offload_status(struct snd_kcontrol *kcontrol,
+				   struct snd_ctl_elem_value *ucontrol)
+{
+	struct snd_soc_component *component = snd_kcontrol_chip(kcontrol);
+	struct snd_soc_usb *ctx = snd_soc_find_usb_ctx(component->dev->of_node);
+	int control_idx = 0;
+	int pcm_idx;
+	int card_idx;
+	int i;
+
+	for (i = 0; i < ctx->num_supported_streams; i++) {
+		card_idx = -1;
+		pcm_idx = -1;
+
+		if (ctx->active_list[i].state == SND_SOC_USB_RUNNING) {
+			card_idx = ctx->active_list[i].active_card_idx;
+			pcm_idx = ctx->active_list[i].active_pcm_idx;
+		}
+
+		ucontrol->value.integer.value[control_idx] = card_idx;
+		control_idx++;
+		ucontrol->value.integer.value[control_idx] = pcm_idx;
+		control_idx++;
+	}
+
+	return 0;
+}
+
+static int snd_soc_usb_offload_status_info(struct snd_kcontrol *kcontrol,
+			      struct snd_ctl_elem_info *uinfo)
+{
+	struct snd_soc_component *component = snd_kcontrol_chip(kcontrol);
+	struct snd_soc_usb *ctx = snd_soc_find_usb_ctx(component->dev->of_node);
+
+	uinfo->type = SNDRV_CTL_ELEM_TYPE_INTEGER;
+	uinfo->count = 2*ctx->num_supported_streams;
+	uinfo->value.integer.min = -1;
+	uinfo->value.integer.max = SNDRV_CARDS;
+
+	return 0;
+}
+
+static const struct snd_kcontrol_new soc_usb_status_ctrl = {
+	.iface = SNDRV_CTL_ELEM_IFACE_CARD,
+	.access = SNDRV_CTL_ELEM_ACCESS_READ,
+	.name = "SNDUSB OFFLD playback status",
+	.info = snd_soc_usb_offload_status_info,
+	.get = snd_soc_usb_get_offload_status,
+	.put = NULL,
+};
+
 static int soc_usb_put_offload_dev(struct snd_kcontrol *kcontrol,
 			      struct snd_ctl_elem_value *ucontrol)
 {
 	struct snd_soc_component *component = snd_kcontrol_chip(kcontrol);
-	struct snd_soc_usb *ctx = snd_soc_usb_find_priv_data(component->dev);
+	struct snd_soc_usb *ctx = snd_soc_find_usb_ctx(component->dev->of_node);
 	int ret = 0;
 
 	mutex_lock(&ctx_mutex);
@@ -61,7 +112,7 @@ static int soc_usb_get_offload_dev(struct snd_kcontrol *kcontrol,
 				   struct snd_ctl_elem_value *ucontrol)
 {
 	struct snd_soc_component *component = snd_kcontrol_chip(kcontrol);
-	struct snd_soc_usb *ctx = snd_soc_usb_find_priv_data(component->dev);
+	struct snd_soc_usb *ctx = snd_soc_find_usb_ctx(component->dev->of_node);
 	int ret = 0;
 
 	mutex_lock(&ctx_mutex);
@@ -95,10 +146,96 @@ static const struct snd_kcontrol_new soc_usb_dev_ctrl = {
 
 static int snd_soc_usb_control_init(struct snd_soc_component *component)
 {
+	int ret;
+
+	ret = snd_ctl_add(component->card->snd_card,
+				snd_ctl_new1(&soc_usb_status_ctrl, component));
+	if (ret < 0)
+		return ret;
+
 	return snd_ctl_add(component->card->snd_card,
 				snd_ctl_new1(&soc_usb_dev_ctrl, component));
 }
 
+/**
+ * snd_soc_usb_set_session_state() - Set the session state for a session
+ * @usb: SOC USB device
+ * @session_id: index to active_list
+ * @state: USB PCM device index
+ *
+ * Set the session state for an entry in active_list.  This should be only
+ * called after snd_soc_usb_prepare_session.
+ *
+ * Returns 0 on success, negative on error.
+ *
+ */
+int snd_soc_usb_set_session_state(struct snd_soc_usb *usb, int session_id,
+				  enum snd_soc_usb_dai_state state)
+{
+	if (session_id < 0 || session_id >= usb->num_supported_streams)
+		return -EINVAL;
+
+	mutex_lock(&ctx_mutex);
+	if (usb->active_list[session_id].state == state) {
+		mutex_unlock(&ctx_mutex);
+		return 0;
+	}
+
+	usb->active_list[session_id].state = state;
+	mutex_unlock(&ctx_mutex);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(snd_soc_usb_set_session_state);
+
+/**
+ * snd_soc_usb_prepare_session() - Find and prepare a session
+ * @usb: SOC USB device
+ * @card_idx: USB card index
+ * @pcm_idx: USB PCM device index
+ *
+ * Find an open active session slot on the SOC USB device.  If all slots
+ * are busy, return an error.  If not, claim the slot and place it into
+ * the SND_SOC_USB_PREPARED state.  This should be called first before
+ * calling snd_soc_usb_set_session_state or snd_soc_usb_shutdown_session.
+ *
+ * Returns the session id (index) to active_list, negative on error.
+ *
+ */
+int snd_soc_usb_prepare_session(struct snd_soc_usb *usb, int card_idx, int pcm_idx)
+{
+	int i;
+
+	mutex_lock(&ctx_mutex);
+	for (i = 0; i < usb->num_supported_streams; i++) {
+		if (usb->active_list[i].state == SND_SOC_USB_IDLE) {
+			usb->active_list[i].active_card_idx = card_idx;
+			usb->active_list[i].active_pcm_idx = pcm_idx;
+			usb->active_list[i].state = SND_SOC_USB_PREPARED;
+			mutex_unlock(&ctx_mutex);
+			return i;
+		}
+	}
+	mutex_unlock(&ctx_mutex);
+
+	return -EBUSY;
+}
+EXPORT_SYMBOL_GPL(snd_soc_usb_prepare_session);
+
+/**
+ * snd_soc_usb_shutdown_session() - Set USB SOC to idle state
+ * @usb: SOC USB device
+ * @session_id: index to active_list
+ *
+ * Place the session specified by session_id into the idle/shutdown state.
+ *
+ */
+int snd_soc_usb_shutdown_session(struct snd_soc_usb *usb, int session_id)
+{
+	return snd_soc_usb_set_session_state(usb, session_id, SND_SOC_USB_IDLE);
+}
+EXPORT_SYMBOL_GPL(snd_soc_usb_shutdown_session);
+
 /**
  * snd_soc_usb_get_components_tag() - Retrieve SOC USB component tag
  * @playback: direction of audio stream
@@ -185,8 +322,16 @@ struct snd_soc_usb *snd_soc_usb_allocate_port(struct snd_soc_component *componen
 	if (!usb)
 		return ERR_PTR(-ENOMEM);
 
+	usb->active_list = kcalloc(num_streams, sizeof(struct snd_soc_usb_session),
+				   GFP_KERNEL);
+	if (!usb->active_list) {
+		kfree(usb);
+		return ERR_PTR(-ENOMEM);
+	}
+
 	usb->component = component;
 	usb->priv_data = data;
+	usb->num_supported_streams = num_streams;
 
 	return usb;
 }
@@ -202,6 +347,7 @@ EXPORT_SYMBOL_GPL(snd_soc_usb_allocate_port);
 void snd_soc_usb_free_port(struct snd_soc_usb *usb)
 {
 	snd_soc_usb_remove_port(usb);
+	kfree(usb->active_list);
 	kfree(usb);
 }
 EXPORT_SYMBOL_GPL(snd_soc_usb_free_port);