[PATCH v16 18/50] ASoC: Add SOC USB APIs for adding an USB backend

@@ -0,0 +1,95 @@
+/* SPDX-License-Identifier: GPL-2.0
+ *
+ * Copyright (c) 2022-2024 Qualcomm Innovation Center, Inc. All rights reserved.
+ */
+
+#ifndef __LINUX_SND_SOC_USB_H
+#define __LINUX_SND_SOC_USB_H
+
+/**
+ * struct snd_soc_usb_device
+ * @card_idx - sound card index associated with USB device
+ * @chip_idx - USB sound chip array index
+ * @num_playback - number of playback streams
+ * @num_capture - number of capture streams
+ **/
+struct snd_soc_usb_device {
+	int card_idx;
+	int chip_idx;
+	int num_playback;
+	int num_capture;
+};
+
+/**
+ * struct snd_soc_usb
+ * @list - list head for SND SOC struct list
+ * @component - reference to ASoC component
+ * @num_supported_streams - number of supported concurrent sessions
+ * @connection_status_cb - callback to notify connection events
+ * @priv_data - driver data
+ **/
+struct snd_soc_usb {
+	struct list_head list;
+	struct snd_soc_component *component;
+	unsigned int num_supported_streams;
+	int (*connection_status_cb)(struct snd_soc_usb *usb,
+			struct snd_soc_usb_device *sdev, bool connected);
+	void *priv_data;
+};
+
+#if IS_ENABLED(CONFIG_SND_SOC_USB)
+const char *snd_soc_usb_get_components_tag(bool playback);
+
+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);
+
+struct snd_soc_usb *snd_soc_usb_allocate_port(struct snd_soc_component *component,
+					      int num_streams, void *data);
+void snd_soc_usb_free_port(struct snd_soc_usb *usb);
+int snd_soc_usb_add_port(struct snd_soc_usb *usb);
+int snd_soc_usb_remove_port(struct snd_soc_usb *usb);
+#else
+static inline const char *snd_soc_usb_get_components_tag(bool playback)
+{
+	return "";
+}
+
+static inline int snd_soc_usb_connect(struct device *usbdev,
+					struct snd_soc_usb_device *sdev)
+{
+	return -ENODEV;
+}
+
+static inline int snd_soc_usb_disconnect(struct device *usbdev,
+					 struct snd_soc_usb_device *sdev)
+{
+	return -EINVAL;
+}
+
+static inline void *snd_soc_usb_find_priv_data(struct device *dev)
+{
+	return NULL;
+}
+
+static inline struct snd_soc_usb *snd_soc_usb_allocate_port(
+					      struct snd_soc_component *component,
+					      int num_streams, void *data)
+{
+	return ERR_PTR(-ENOMEM);
+}
+
+static inline void snd_soc_usb_free_port(struct snd_soc_usb *usb)
+{ }
+
+static inline int snd_soc_usb_add_port(struct snd_soc_usb *usb)
+{
+	return -EINVAL;
+}
+
+static inline int snd_soc_usb_remove_port(struct snd_soc_usb *usb)
+{
+	return -ENODEV;
+}
+#endif /* IS_ENABLED(CONFIG_SND_SOC_USB) */
+#endif /*__LINUX_SND_SOC_USB_H */

@@ -76,6 +76,15 @@ config SND_SOC_UTILS_KUNIT_TEST
 config SND_SOC_ACPI
 	tristate
 
+config SND_SOC_USB
+	tristate "SoC based USB audio offloading"
+	help
+	  Enable this option if an ASoC platform card has support to handle
+	  USB audio offloading.  This enables the SoC USB layer, which will
+	  notifies the ASoC USB DPCM backend DAI link about available USB audio
+	  devices.  Based on the notifications, sequences to enable the audio
+	  stream can be taken based on the design.
+
 # All the supported SoCs
 source "sound/soc/adi/Kconfig"
 source "sound/soc/amd/Kconfig"

@@ -31,6 +31,8 @@ endif
 
 obj-$(CONFIG_SND_SOC_ACPI) += snd-soc-acpi.o
 
+obj-$(CONFIG_SND_SOC_USB) += soc-usb.o
+
 obj-$(CONFIG_SND_SOC)	+= snd-soc-core.o
 obj-$(CONFIG_SND_SOC)	+= codecs/
 obj-$(CONFIG_SND_SOC)	+= generic/

@@ -0,0 +1,239 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2022-2024 Qualcomm Innovation Center, Inc. All rights reserved.
+ */
+#include <linux/of.h>
+#include <linux/usb.h>
+#include <sound/soc.h>
+#include <sound/soc-usb.h>
+#include "../usb/card.h"
+
+static DEFINE_MUTEX(ctx_mutex);
+static LIST_HEAD(usb_ctx_list);
+
+static struct device_node *snd_soc_find_phandle(struct device *dev)
+{
+	struct device_node *node;
+
+	node = of_parse_phandle(dev->of_node, "usb-soc-be", 0);
+	if (!node)
+		return ERR_PTR(-ENODEV);
+
+	return node;
+}
+
+static struct snd_soc_usb *snd_soc_find_usb_ctx(struct device_node *node)
+{
+	struct snd_soc_usb *ctx;
+
+	mutex_lock(&ctx_mutex);
+	list_for_each_entry(ctx, &usb_ctx_list, list) {
+		if (ctx->component->dev->of_node == node) {
+			mutex_unlock(&ctx_mutex);
+			return ctx;
+		}
+	}
+	mutex_unlock(&ctx_mutex);
+
+	return NULL;
+}
+
+/**
+ * snd_soc_usb_get_components_tag() - Retrieve SOC USB component tag
+ * @playback: direction of audio stream
+ *
+ * Returns the USB offload component tag used in the ASoC components
+ * string.
+ *
+ */
+const char *snd_soc_usb_get_components_tag(bool playback)
+{
+	if (playback)
+		return "usbplybkoffld: 1";
+	else
+		return "usbcapoffld: 1";
+}
+EXPORT_SYMBOL_GPL(snd_soc_usb_get_components_tag);
+
+/**
+ * snd_soc_usb_find_priv_data() - Retrieve private data stored
+ * @dev: device reference
+ *
+ * Fetch the private data stored in the USB SND SOC structure.
+ *
+ */
+void *snd_soc_usb_find_priv_data(struct device *dev)
+{
+	struct snd_soc_usb *ctx;
+	struct device_node *node;
+
+	node = snd_soc_find_phandle(dev);
+	if (!IS_ERR(node)) {
+		ctx = snd_soc_find_usb_ctx(node);
+		of_node_put(node);
+	} else {
+		/* Check if backend device */
+		ctx = snd_soc_find_usb_ctx(dev->of_node);
+	}
+
+	return ctx ? ctx->priv_data : NULL;
+}
+EXPORT_SYMBOL_GPL(snd_soc_usb_find_priv_data);
+
+/**
+ * snd_soc_usb_allocate_port() - allocate a SOC USB device
+ * @component: USB DPCM backend DAI component
+ * @num_streams: number of offloading sessions supported
+ * @data: private data
+ *
+ * Allocate and initialize a SOC USB device.  This will populate parameters that
+ * are used in subsequent sequences.
+ *
+ */
+struct snd_soc_usb *snd_soc_usb_allocate_port(struct snd_soc_component *component,
+					      int num_streams, void *data)
+{
+	struct snd_soc_usb *usb;
+
+	usb = kzalloc(sizeof(*usb), GFP_KERNEL);
+	if (!usb)
+		return ERR_PTR(-ENOMEM);
+
+	usb->component = component;
+	usb->priv_data = data;
+	usb->num_supported_streams = num_streams;
+
+	return usb;
+}
+EXPORT_SYMBOL_GPL(snd_soc_usb_allocate_port);
+
+/**
+ * snd_soc_usb_free_port() - free a SOC USB device
+ * @usb: allocated SOC USB device
+
+ * Free and remove the SOC USB device from the available list of devices.
+ *
+ */
+void snd_soc_usb_free_port(struct snd_soc_usb *usb)
+{
+	snd_soc_usb_remove_port(usb);
+	kfree(usb);
+}
+EXPORT_SYMBOL_GPL(snd_soc_usb_free_port);
+
+/**
+ * snd_soc_usb_add_port() - Add a USB backend port
+ * @dev: USB backend device
+ * @priv: private data
+ * @connection_cb: connection status callback
+ *
+ * Register a USB backend device to the SND USB SOC framework.  Memory is
+ * allocated as part of the USB backend device.
+ *
+ */
+int snd_soc_usb_add_port(struct snd_soc_usb *usb)
+{
+	mutex_lock(&ctx_mutex);
+	list_add_tail(&usb->list, &usb_ctx_list);
+	mutex_unlock(&ctx_mutex);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(snd_soc_usb_add_port);
+
+/**
+ * snd_soc_usb_remove_port() - Remove a USB backend port
+ * @dev: USB backend device
+ *
+ * Remove a USB backend device from USB SND SOC.  Memory is freed when USB
+ * backend is removed.
+ *
+ */
+int snd_soc_usb_remove_port(struct snd_soc_usb *usb)
+{
+	struct snd_soc_usb *ctx, *tmp;
+
+	mutex_lock(&ctx_mutex);
+	list_for_each_entry_safe(ctx, tmp, &usb_ctx_list, list) {
+		if (ctx == usb) {
+			list_del(&ctx->list);
+			break;
+		}
+	}
+	mutex_unlock(&ctx_mutex);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(snd_soc_usb_remove_port);
+
+/**
+ * snd_soc_usb_connect() - Notification of USB device connection
+ * @usbdev: USB bus device
+ * @card_idx: USB SND card instance
+ *
+ * Notify of a new USB SND device connection.  The card_idx can be used to
+ * handle how the DPCM backend selects, which device to enable USB offloading
+ * on.
+ *
+ */
+int snd_soc_usb_connect(struct device *usbdev, struct snd_soc_usb_device *sdev)
+{
+	struct snd_soc_usb *ctx;
+	struct device_node *node;
+
+	if (!usbdev)
+		return -ENODEV;
+
+	node = snd_soc_find_phandle(usbdev);
+	if (IS_ERR(node))
+		return -ENODEV;
+
+	ctx = snd_soc_find_usb_ctx(node);
+	of_node_put(node);
+	if (!ctx)
+		return -ENODEV;
+
+	mutex_lock(&ctx_mutex);
+	if (ctx->connection_status_cb)
+		ctx->connection_status_cb(ctx, sdev, true);
+	mutex_unlock(&ctx_mutex);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(snd_soc_usb_connect);
+
+/**
+ * snd_soc_usb_disconnect() - Notification of USB device disconnection
+ * @usbdev: USB bus device
+ *
+ * Notify of a new USB SND device disconnection to the USB backend.
+ *
+ */
+int snd_soc_usb_disconnect(struct device *usbdev, struct snd_soc_usb_device *sdev)
+{
+	struct snd_soc_usb *ctx;
+	struct device_node *node;
+
+	if (!usbdev)
+		return -ENODEV;
+
+	node = snd_soc_find_phandle(usbdev);
+	if (IS_ERR(node))
+		return -ENODEV;
+
+	ctx = snd_soc_find_usb_ctx(node);
+	of_node_put(node);
+	if (!ctx)
+		return -ENODEV;
+
+	mutex_lock(&ctx_mutex);
+	if (ctx->connection_status_cb)
+		ctx->connection_status_cb(ctx, sdev, false);
+	mutex_unlock(&ctx_mutex);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(snd_soc_usb_disconnect);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("SoC USB driver for offloading");