[PATCH v19 29/41] ASoC: Introduce SND kcontrols to select sound card and PCM device

[Wesley Cheng]

Add SND kcontrol to SOC USB, which will allow for userpsace to determine
which USB card number and PCM device to offload.  This allows for userspace
to potentially tag an alternate path for a specific USB SND card and PCM
device.  Previously, control was absent, and the offload path would be
enabled on the last USB SND device which was connected.  This logic will
continue to be applicable if no mixer input is received for specific device
selection.

An example to configure the offload device using tinymix:
tinymix -D 0 set 'USB Offload Playback Route Select' 1 0

The above command will configure the offload path to utilize card#1 and PCM
stream#0.

Signed-off-by: Wesley Cheng <quic_wcheng@xxxxxxxxxxx>
---
 include/sound/soc-usb.h |  16 ++++
 sound/soc/soc-usb.c     | 157 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 173 insertions(+)

diff --git a/include/sound/soc-usb.h b/include/sound/soc-usb.h
index 8f2d3064b520..18cdc59df9aa 100644
--- a/include/sound/soc-usb.h
+++ b/include/sound/soc-usb.h
@@ -6,6 +6,12 @@
 #ifndef __LINUX_SND_SOC_USB_H
 #define __LINUX_SND_SOC_USB_H
 
+enum snd_soc_usb_kctl {
+	SND_SOC_USB_KCTL_CARD_ROUTE,
+	SND_SOC_USB_KCTL_PCM_ROUTE,
+	SND_SOC_USB_KCTL_MAX,
+};
+
 /**
  * struct snd_soc_usb_device
  * @card_idx - sound card index associated with USB device
@@ -24,16 +30,26 @@ struct snd_soc_usb_device {
  * struct snd_soc_usb
  * @list - list head for SND SOC struct list
  * @component - reference to ASoC component
+ * @kctl - list of kcontrols created
  * @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
  * @priv_data - driver data
  **/
 struct snd_soc_usb {
 	struct list_head list;
 	struct snd_soc_component *component;
+	struct snd_kcontrol *kctl[SND_SOC_USB_KCTL_MAX];
 	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,
+			       struct snd_ctl_elem_value *ucontrol,
+			       enum snd_soc_usb_kctl type);
+	int (*get_offload_dev)(struct snd_kcontrol *kcontrol,
+			       struct snd_ctl_elem_value *ucontrol,
+			       enum snd_soc_usb_kctl type);
 	void *priv_data;
 };
 
diff --git a/sound/soc/soc-usb.c b/sound/soc/soc-usb.c
index bc77204fd2db..ade09b416d45 100644
--- a/sound/soc/soc-usb.c
+++ b/sound/soc/soc-usb.c
@@ -15,6 +15,9 @@ static struct device_node *snd_soc_find_phandle(struct device *dev)
 {
 	struct device_node *node;
 
+	if (!dev)
+		return ERR_PTR(-ENODEV);
+
 	node = of_parse_phandle(dev->of_node, "usb-soc-be", 0);
 	if (!node)
 		return ERR_PTR(-ENODEV);
@@ -38,6 +41,152 @@ static struct snd_soc_usb *snd_soc_find_usb_ctx(struct device_node *node)
 	return NULL;
 }
 
+/* SOC USB sound kcontrols */
+static int soc_usb_put_offload_pcm_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_find_usb_ctx(component->dev->of_node);
+	int ret = 0;
+
+	mutex_lock(&ctx_mutex);
+	if (ctx && ctx->put_offload_dev)
+		ret = ctx->put_offload_dev(kcontrol, ucontrol,
+						SND_SOC_USB_KCTL_PCM_ROUTE);
+	mutex_unlock(&ctx_mutex);
+
+	return ret;
+}
+
+static int soc_usb_get_offload_pcm_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_find_usb_ctx(component->dev->of_node);
+	int ret = 0;
+
+	ucontrol->value.integer.value[0] = -1;
+
+	mutex_lock(&ctx_mutex);
+	if (ctx && ctx->get_offload_dev)
+		ret = ctx->get_offload_dev(kcontrol, ucontrol,
+						SND_SOC_USB_KCTL_PCM_ROUTE);
+	mutex_unlock(&ctx_mutex);
+
+	return ret;
+
+}
+
+static int soc_usb_put_offload_card_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_find_usb_ctx(component->dev->of_node);
+	int ret = 0;
+
+	mutex_lock(&ctx_mutex);
+	if (ctx && ctx->put_offload_dev)
+		ret = ctx->put_offload_dev(kcontrol, ucontrol,
+						SND_SOC_USB_KCTL_CARD_ROUTE);
+	mutex_unlock(&ctx_mutex);
+
+	return ret;
+}
+
+static int soc_usb_get_offload_card_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_find_usb_ctx(component->dev->of_node);
+	int ret = 0;
+
+	ucontrol->value.integer.value[0] = -1;
+
+	mutex_lock(&ctx_mutex);
+	if (ctx && ctx->get_offload_dev)
+		ret = ctx->get_offload_dev(kcontrol, ucontrol,
+						SND_SOC_USB_KCTL_CARD_ROUTE);
+	mutex_unlock(&ctx_mutex);
+
+	return ret;
+
+}
+
+static int soc_usb_offload_pcm_info(struct snd_kcontrol *kcontrol,
+			      struct snd_ctl_elem_info *uinfo)
+{
+	uinfo->type = SNDRV_CTL_ELEM_TYPE_INTEGER;
+	uinfo->count = 1;
+	uinfo->value.integer.min = -1;
+	/* Arbitrary max value, as there is no 'limit' on number of PCM devices */
+	uinfo->value.integer.max = 0xff;
+
+	return 0;
+}
+
+static int soc_usb_offload_card_info(struct snd_kcontrol *kcontrol,
+			      struct snd_ctl_elem_info *uinfo)
+{
+	uinfo->type = SNDRV_CTL_ELEM_TYPE_INTEGER;
+	uinfo->count = 1;
+	uinfo->value.integer.min = -1;
+	uinfo->value.integer.max = SNDRV_CARDS;
+
+	return 0;
+}
+
+static const struct snd_kcontrol_new soc_usb_kcontrols[] = {
+	[SND_SOC_USB_KCTL_CARD_ROUTE] = {
+		.iface = SNDRV_CTL_ELEM_IFACE_CARD,
+		.access = SNDRV_CTL_ELEM_ACCESS_READWRITE,
+		.name = "USB Offload Playback Route Card Select",
+		.info = soc_usb_offload_card_info,
+		.get = soc_usb_get_offload_card_dev,
+		.put = soc_usb_put_offload_card_dev,
+	},
+	[SND_SOC_USB_KCTL_PCM_ROUTE] = {
+		.iface = SNDRV_CTL_ELEM_IFACE_CARD,
+		.access = SNDRV_CTL_ELEM_ACCESS_READWRITE,
+		.name = "USB Offload Playback Route PCM Select",
+		.info = soc_usb_offload_pcm_info,
+		.get = soc_usb_get_offload_pcm_dev,
+		.put = soc_usb_put_offload_pcm_dev,
+	},
+};
+
+static int snd_soc_usb_control_remove(struct snd_soc_usb *usb)
+{
+	struct snd_soc_component *component = usb->component;
+	int i;
+
+	for (i = 0; i < SND_SOC_USB_KCTL_MAX; i++) {
+		if (usb->kctl[i]) {
+			snd_ctl_remove(component->card->snd_card,
+					usb->kctl[i]);
+			snd_ctl_free_one(usb->kctl[i]);
+			usb->kctl[i] = NULL;
+		}
+	}
+
+	return 0;
+}
+
+static int snd_soc_usb_control_init(struct snd_soc_usb *usb)
+{
+	struct snd_soc_component *component = usb->component;
+	int ret;
+	int i;
+
+	for (i = 0; i < SND_SOC_USB_KCTL_MAX; i++) {
+		usb->kctl[i] = snd_ctl_new1(&soc_usb_kcontrols[i], component);
+		ret = snd_ctl_add(component->card->snd_card, usb->kctl[i]);
+		if (ret < 0)
+			return ret;
+	}
+
+	return ret;
+}
+
 /**
  * snd_soc_usb_get_components_tag() - Retrieve SOC USB component tag
  * @playback: direction of audio stream
@@ -158,6 +307,12 @@ EXPORT_SYMBOL_GPL(snd_soc_usb_free_port);
  */
 int snd_soc_usb_add_port(struct snd_soc_usb *usb)
 {
+	int ret;
+
+	ret = snd_soc_usb_control_init(usb);
+	if (ret < 0)
+		return ret;
+
 	mutex_lock(&ctx_mutex);
 	list_add_tail(&usb->list, &usb_ctx_list);
 	mutex_unlock(&ctx_mutex);
@@ -187,6 +342,8 @@ int snd_soc_usb_remove_port(struct snd_soc_usb *usb)
 	}
 	mutex_unlock(&ctx_mutex);
 
+	snd_soc_usb_control_remove(usb);
+
 	return 0;
 }
 EXPORT_SYMBOL_GPL(snd_soc_usb_remove_port);