[RFC PATCH 01/14] ASoC: Add SOC USB APIs for adding an USB backend

[Wesley Cheng]

Some platforms may want to register its USB port to be handled by the ASoC
framework.  Audio playback/capture support is also handled entirely by the
vendor ASoC drivers.

Signed-off-by: Wesley Cheng <quic_wcheng at quicinc.com>
---
 include/sound/soc-usb.h | 31 +++++++++++++++++++
 sound/soc/Makefile      |  2 +-
 sound/soc/soc-usb.c     | 66 +++++++++++++++++++++++++++++++++++++++++
 3 files changed, 98 insertions(+), 1 deletion(-)
 create mode 100644 include/sound/soc-usb.h
 create mode 100644 sound/soc/soc-usb.c

diff --git a/include/sound/soc-usb.h b/include/sound/soc-usb.h
new file mode 100644
index 000000000000..7d52e5d2371c
--- /dev/null
+++ b/include/sound/soc-usb.h
@@ -0,0 +1,31 @@
+/* SPDX-License-Identifier: GPL-2.0
+ *
+ * Copyright (c) 2022 Qualcomm Innovation Center, Inc. All rights reserved.
+ */
+
+#ifndef __LINUX_SND_SOC_USB_H
+#define __LINUX_SND_SOC_USB_H
+
+/**
+ * struct snd_soc_usb
+ * @component - Reference to DAPM component
+ * @connection_status_cb - callback to notify connection events
+ * @priv_data - vendor data
+ **/
+struct snd_soc_usb {
+	struct snd_soc_component *component;
+	int (*connection_status_cb)(struct snd_soc_usb *usb, int card_idx,
+				int connected);
+	void *priv_data;
+};
+
+int snd_soc_usb_connect(int card_idx);
+int snd_soc_usb_disconnect(void);
+void snd_soc_usb_set_priv_data(void *priv);
+void *snd_soc_usb_get_priv_data(void);
+
+struct snd_soc_usb *snd_soc_usb_add_port(struct device *dev,
+			int (*connection_cb)(struct snd_soc_usb *usb, int card_idx,
+			int connected));
+int snd_soc_usb_remove_port(void);
+#endif
diff --git a/sound/soc/Makefile b/sound/soc/Makefile
index 507eaed1d6a1..3305ceb59d84 100644
--- a/sound/soc/Makefile
+++ b/sound/soc/Makefile
@@ -1,5 +1,5 @@
 # SPDX-License-Identifier: GPL-2.0
-snd-soc-core-objs := soc-core.o soc-dapm.o soc-jack.o soc-utils.o soc-dai.o soc-component.o
+snd-soc-core-objs := soc-core.o soc-dapm.o soc-jack.o soc-usb.o soc-utils.o soc-dai.o soc-component.o
 snd-soc-core-objs += soc-pcm.o soc-devres.o soc-ops.o soc-link.o soc-card.o
 snd-soc-core-$(CONFIG_SND_SOC_COMPRESS) += soc-compress.o
 
diff --git a/sound/soc/soc-usb.c b/sound/soc/soc-usb.c
new file mode 100644
index 000000000000..c6c376960e4d
--- /dev/null
+++ b/sound/soc/soc-usb.c
@@ -0,0 +1,66 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2022 Qualcomm Innovation Center, Inc. All rights reserved.
+ */
+#include <linux/usb.h>
+#include <sound/soc.h>
+#include <sound/soc-usb.h>
+#include "../usb/card.h"
+
+struct snd_soc_usb *ctx;
+
+void *snd_soc_usb_get_priv_data(void)
+{
+	if (ctx)
+		return ctx->priv_data;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(snd_soc_usb_get_priv_data);
+
+void snd_soc_usb_set_priv_data(void *priv)
+{
+	if (ctx)
+		ctx->priv_data = priv;
+}
+EXPORT_SYMBOL_GPL(snd_soc_usb_set_priv_data);
+
+struct snd_soc_usb *snd_soc_usb_add_port(struct device *dev,
+			int (*connection_cb)(struct snd_soc_usb *usb, int card_idx,
+			int connected))
+{
+	struct snd_soc_usb *usb;
+
+	usb = devm_kzalloc(dev, sizeof(*usb), GFP_KERNEL);
+	if (!usb)
+		return ERR_PTR(-ENOMEM);
+
+	usb->connection_status_cb = connection_cb;
+	ctx = usb;
+
+	return usb;
+}
+EXPORT_SYMBOL_GPL(snd_soc_usb_add_port);
+
+int snd_soc_usb_remove_port(void)
+{
+	ctx = NULL;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(snd_soc_usb_remove_port);
+
+int snd_soc_usb_connect(int card_idx)
+{
+	if (ctx && ctx->connection_status_cb)
+		ctx->connection_status_cb(ctx, card_idx, 1);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(snd_soc_usb_connect);
+
+int snd_soc_usb_disconnect(void)
+{
+	if (ctx && ctx->connection_status_cb)
+		ctx->connection_status_cb(ctx, -1, 0);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(snd_soc_usb_disconnect);