USB: gadget: add USB Audio Gadget driver

Funtions added:
 - setup all the USB audio class device descriptors
 - handle class specific setup request
 - receive data from USB host by ISO transfer
 - play audio data by ALSA sound card
 - open and setup playback PCM interface
 - set default playback PCM parameters
 - provide playback functions for USB audio driver
 - provide PCM parameters set/get functions

Test on:
 - Host: Ubuntu 8.10, kernel 2.6.27
 - Gadget: EZKIT-BF548 with ASoC AD1980 codec

Todo:
 - add real Mute control code
 - add real Volume control code
 - maybe find another way to replace dynamic buffer handling
   with static buffer allocation
 - test on Windows system
 - provide control interface to handle mute/volume control
 - provide capture interface in the future
 - test on BF527, other USB device controler and other audio codec

Signed-off-by: Bryan Wu <cooloney@kernel.org>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

6 files changed, 1400 insertions, 0 deletions

diff --git a/drivers/usb/gadget/Kconfig b/drivers/usb/gadget/Kconfig
index 924bb7a..ef9d908 100644
--- a/drivers/usb/gadget/Kconfig
+++ b/drivers/usb/gadget/Kconfig
@@ -580,6 +580,20 @@ config USB_ZERO_HNPTEST
 	  the "B-Peripheral" role, that device will use HNP to let this
 	  one serve as the USB host instead (in the "B-Host" role).
 
+config USB_AUDIO
+	tristate "Audio Gadget (EXPERIMENTAL)"
+	depends on SND
+	help
+	  Gadget Audio is compatible with USB Audio Class specification 1.0.
+	  It will include at least one AudioControl interface, zero or more
+	  AudioStream interface and zero or more MIDIStream interface.
+
+	  Gadget Audio will use on-board ALSA (CONFIG_SND) audio card to
+	  playback or capture audio stream.
+
+	  Say "y" to link the driver statically, or "m" to build a
+	  dynamically linked module called "g_audio".
+
 config USB_ETH
 	tristate "Ethernet Gadget (with CDC Ethernet support)"
 	depends on NET
diff --git a/drivers/usb/gadget/Makefile b/drivers/usb/gadget/Makefile
index 9be2fbd..fc9a7dc 100644
--- a/drivers/usb/gadget/Makefile
+++ b/drivers/usb/gadget/Makefile
@@ -31,6 +31,7 @@ obj-$(CONFIG_USB_S3C_HSOTG)	+= s3c-hsotg.o
 # USB gadget drivers
 #
 g_zero-objs			:= zero.o
+g_audio-objs			:= audio.o
 g_ether-objs			:= ether.o
 g_serial-objs			:= serial.o
 g_midi-objs			:= gmidi.o
@@ -40,6 +41,7 @@ g_printer-objs			:= printer.o
 g_cdc-objs			:= cdc2.o
 
 obj-$(CONFIG_USB_ZERO)		+= g_zero.o
+obj-$(CONFIG_USB_AUDIO)		+= g_audio.o
 obj-$(CONFIG_USB_ETH)		+= g_ether.o
 obj-$(CONFIG_USB_GADGETFS)	+= gadgetfs.o
 obj-$(CONFIG_USB_FILE_STORAGE)	+= g_file_storage.o
diff --git a/drivers/usb/gadget/audio.c b/drivers/usb/gadget/audio.c
new file mode 100644
index 0000000..94de7e8
--- /dev/null
+++ b/drivers/usb/gadget/audio.c
@@ -0,0 +1,302 @@
+/*
+ * audio.c -- Audio gadget driver
+ *
+ * Copyright (C) 2008 Bryan Wu <cooloney@kernel.org>
+ * Copyright (C) 2008 Analog Devices, Inc
+ *
+ * Enter bugs at http://blackfin.uclinux.org/
+ *
+ * Licensed under the GPL-2 or later.
+ */
+
+/* #define VERBOSE_DEBUG */
+
+#include <linux/kernel.h>
+#include <linux/utsname.h>
+
+#include "u_audio.h"
+
+#define DRIVER_DESC		"Linux USB Audio Gadget"
+#define DRIVER_VERSION		"Dec 18, 2008"
+
+/*-------------------------------------------------------------------------*/
+
+/*
+ * Kbuild is not very cooperative with respect to linking separately
+ * compiled library objects into one module.  So for now we won't use
+ * separate compilation ... ensuring init/exit sections work to shrink
+ * the runtime footprint, and giving us at least some parts of what
+ * a "gcc --combine ... part1.c part2.c part3.c ... " build would.
+ */
+#include "composite.c"
+#include "usbstring.c"
+#include "config.c"
+#include "epautoconf.c"
+
+#include "u_audio.c"
+#include "f_audio.c"
+
+/*-------------------------------------------------------------------------*/
+
+/* DO NOT REUSE THESE IDs with a protocol-incompatible driver!!  Ever!!
+ * Instead:  allocate your own, using normal USB-IF procedures.
+ */
+
+/* Thanks to NetChip Technologies for donating this product ID. */
+#define AUDIO_VENDOR_NUM		0x0525	/* NetChip */
+#define AUDIO_PRODUCT_NUM		0xa4a1	/* Linux-USB Audio Gadget */
+
+/*-------------------------------------------------------------------------*/
+
+static struct usb_device_descriptor device_desc = {
+	.bLength =		sizeof device_desc,
+	.bDescriptorType =	USB_DT_DEVICE,
+
+	.bcdUSB =		__constant_cpu_to_le16(0x200),
+
+	.bDeviceClass =		USB_CLASS_PER_INTERFACE,
+	.bDeviceSubClass =	0,
+	.bDeviceProtocol =	0,
+	/* .bMaxPacketSize0 = f(hardware) */
+
+	/* Vendor and product id defaults change according to what configs
+	 * we support.  (As does bNumConfigurations.)  These values can
+	 * also be overridden by module parameters.
+	 */
+	.idVendor =		__constant_cpu_to_le16(AUDIO_VENDOR_NUM),
+	.idProduct =		__constant_cpu_to_le16(AUDIO_PRODUCT_NUM),
+	/* .bcdDevice = f(hardware) */
+	/* .iManufacturer = DYNAMIC */
+	/* .iProduct = DYNAMIC */
+	/* NO SERIAL NUMBER */
+	.bNumConfigurations =	1,
+};
+
+static struct usb_otg_descriptor otg_descriptor = {
+	.bLength =		sizeof otg_descriptor,
+	.bDescriptorType =	USB_DT_OTG,
+
+	/* REVISIT SRP-only hardware is possible, although
+	 * it would not be called "OTG" ...
+	 */
+	.bmAttributes =		USB_OTG_SRP | USB_OTG_HNP,
+};
+
+static const struct usb_descriptor_header *otg_desc[] = {
+	(struct usb_descriptor_header *) &otg_descriptor,
+	NULL,
+};
+
+/*-------------------------------------------------------------------------*/
+
+/**
+ * Handle USB audio endpoint set/get command in setup class request
+ */
+
+static int audio_set_endpoint_req(struct usb_configuration *c,
+		const struct usb_ctrlrequest *ctrl)
+{
+	struct usb_composite_dev *cdev = c->cdev;
+	int			value = -EOPNOTSUPP;
+	u16			ep = le16_to_cpu(ctrl->wIndex);
+	u16			len = le16_to_cpu(ctrl->wLength);
+	u16			w_value = le16_to_cpu(ctrl->wValue);
+
+	DBG(cdev, "bRequest 0x%x, w_value 0x%04x, len %d, endpoint %d\n",
+			ctrl->bRequest, w_value, len, ep);
+
+	switch (ctrl->bRequest) {
+	case SET_CUR:
+		value = 0;
+		break;
+
+	case SET_MIN:
+		break;
+
+	case SET_MAX:
+		break;
+
+	case SET_RES:
+		break;
+
+	case SET_MEM:
+		break;
+
+	default:
+		break;
+	}
+
+	return value;
+}
+
+static int audio_get_endpoint_req(struct usb_configuration *c,
+		const struct usb_ctrlrequest *ctrl)
+{
+	struct usb_composite_dev *cdev = c->cdev;
+	int value = -EOPNOTSUPP;
+	u8 ep = ((le16_to_cpu(ctrl->wIndex) >> 8) & 0xFF);
+	u16 len = le16_to_cpu(ctrl->wLength);
+	u16 w_value = le16_to_cpu(ctrl->wValue);
+
+	DBG(cdev, "bRequest 0x%x, w_value 0x%04x, len %d, endpoint %d\n",
+			ctrl->bRequest, w_value, len, ep);
+
+	switch (ctrl->bRequest) {
+	case GET_CUR:
+	case GET_MIN:
+	case GET_MAX:
+	case GET_RES:
+		value = 3;
+		break;
+	case GET_MEM:
+		break;
+	default:
+		break;
+	}
+
+	return value;
+}
+
+static int
+audio_setup(struct usb_configuration *c, const struct usb_ctrlrequest *ctrl)
+{
+	struct usb_composite_dev *cdev = c->cdev;
+	struct usb_request *req = cdev->req;
+	int value = -EOPNOTSUPP;
+	u16 w_index = le16_to_cpu(ctrl->wIndex);
+	u16 w_value = le16_to_cpu(ctrl->wValue);
+	u16 w_length = le16_to_cpu(ctrl->wLength);
+
+	/* composite driver infrastructure handles everything except
+	 * Audio class messages; interface activation uses set_alt().
+	 */
+	switch (ctrl->bRequestType) {
+	case USB_AUDIO_SET_ENDPOINT:
+		value = audio_set_endpoint_req(c, ctrl);
+		break;
+
+	case USB_AUDIO_GET_ENDPOINT:
+		value = audio_get_endpoint_req(c, ctrl);
+		break;
+
+	default:
+		ERROR(cdev, "Invalid control req%02x.%02x v%04x i%04x l%d\n",
+			ctrl->bRequestType, ctrl->bRequest,
+			w_value, w_index, w_length);
+	}
+
+	/* respond with data transfer or status phase? */
+	if (value >= 0) {
+		DBG(cdev, "Audio req%02x.%02x v%04x i%04x l%d\n",
+			ctrl->bRequestType, ctrl->bRequest,
+			w_value, w_index, w_length);
+		req->zero = 0;
+		req->length = value;
+		value = usb_ep_queue(cdev->gadget->ep0, req, GFP_ATOMIC);
+		if (value < 0)
+			ERROR(cdev, "Audio response on err %d\n", value);
+	}
+
+	/* device either stalls (value < 0) or reports success */
+	return value;
+}
+
+/*-------------------------------------------------------------------------*/
+
+static int __init audio_do_config(struct usb_configuration *c)
+{
+	/* FIXME alloc iConfiguration string, set it in c->strings */
+
+	if (gadget_is_otg(c->cdev->gadget)) {
+		c->descriptors = otg_desc;
+		c->bmAttributes |= USB_CONFIG_ATT_WAKEUP;
+	}
+
+	audio_bind_config(c);
+
+	return 0;
+}
+
+static struct usb_configuration audio_config_driver = {
+	.label			= DRIVER_DESC,
+	.bind			= audio_do_config,
+	.setup			= audio_setup,
+	.bConfigurationValue	= 1,
+	/* .iConfiguration = DYNAMIC */
+	.bmAttributes		= USB_CONFIG_ATT_SELFPOWER,
+};
+
+/*-------------------------------------------------------------------------*/
+
+static int __init audio_bind(struct usb_composite_dev *cdev)
+{
+	int			gcnum;
+	int			status;
+
+	gcnum = usb_gadget_controller_number(cdev->gadget);
+	if (gcnum >= 0)
+		device_desc.bcdDevice = cpu_to_le16(0x0300 | gcnum);
+	else {
+		ERROR(cdev, "controller '%s' not recognized; trying %s\n",
+			cdev->gadget->name,
+			audio_config_driver.label);
+		device_desc.bcdDevice =
+			__constant_cpu_to_le16(0x0300 | 0x0099);
+	}
+
+	/* device descriptor strings: manufacturer, product */
+	snprintf(manufacturer, sizeof manufacturer, "%s %s with %s",
+		init_utsname()->sysname, init_utsname()->release,
+		cdev->gadget->name);
+	status = usb_string_id(cdev);
+	if (status < 0)
+		goto fail;
+	strings_dev[STRING_MANUFACTURER_IDX].id = status;
+	device_desc.iManufacturer = status;
+
+	status = usb_string_id(cdev);
+	if (status < 0)
+		goto fail;
+	strings_dev[STRING_PRODUCT_IDX].id = status;
+	device_desc.iProduct = status;
+
+	status = usb_add_config(cdev, &audio_config_driver);
+	if (status < 0)
+		goto fail;
+
+	INFO(cdev, "%s, version: %s\n", DRIVER_DESC, DRIVER_VERSION);
+	return 0;
+
+fail:
+	return status;
+}
+
+static int __exit audio_unbind(struct usb_composite_dev *cdev)
+{
+	return 0;
+}
+
+static struct usb_composite_driver audio_driver = {
+	.name		= "g_audio",
+	.dev		= &device_desc,
+	.strings	= audio_strings,
+	.bind		= audio_bind,
+	.unbind		= __exit_p(audio_unbind),
+};
+
+static int __init init(void)
+{
+	return usb_composite_register(&audio_driver);
+}
+module_init(init);
+
+static void __exit cleanup(void)
+{
+	usb_composite_unregister(&audio_driver);
+}
+module_exit(cleanup);
+
+MODULE_DESCRIPTION(DRIVER_DESC);
+MODULE_AUTHOR("Bryan Wu <cooloney@kernel.org>");
+MODULE_LICENSE("GPL");
+
diff --git a/drivers/usb/gadget/f_audio.c b/drivers/usb/gadget/f_audio.c
new file mode 100644
index 0000000..66527ba
--- /dev/null
+++ b/drivers/usb/gadget/f_audio.c
@@ -0,0 +1,707 @@
+/*
+ * f_audio.c -- USB Audio class function driver
+  *
+ * Copyright (C) 2008 Bryan Wu <cooloney@kernel.org>
+ * Copyright (C) 2008 Analog Devices, Inc
+ *
+ * Enter bugs at http://blackfin.uclinux.org/
+ *
+ * Licensed under the GPL-2 or later.
+ */
+
+#include <linux/kernel.h>
+#include <linux/device.h>
+#include <asm/atomic.h>
+
+#include "u_audio.h"
+
+#define OUT_EP_MAX_PACKET_SIZE	200
+static int req_buf_size = OUT_EP_MAX_PACKET_SIZE;
+module_param(req_buf_size, int, S_IRUGO);
+MODULE_PARM_DESC(req_buf_size, "ISO OUT endpoint request buffer size");
+
+static int req_count = 256;
+module_param(req_count, int, S_IRUGO);
+MODULE_PARM_DESC(req_count, "ISO OUT endpoint request count");
+
+static int audio_buf_size = 48000;
+module_param(audio_buf_size, int, S_IRUGO);
+MODULE_PARM_DESC(audio_buf_size, "Audio buffer size");
+
+/*
+ * DESCRIPTORS ... most are static, but strings and full
+ * configuration descriptors are built on demand.
+ */
+
+/*
+ * We have two interfaces- AudioControl and AudioStreaming
+ * TODO: only supcard playback currently
+ */
+#define F_AUDIO_AC_INTERFACE	0
+#define F_AUDIO_AS_INTERFACE	1
+#define F_AUDIO_NUM_INTERFACES	2
+
+/* B.3.1  Standard AC Interface Descriptor */
+static struct usb_interface_descriptor ac_interface_desc __initdata = {
+	.bLength =		USB_DT_INTERFACE_SIZE,
+	.bDescriptorType =	USB_DT_INTERFACE,
+	.bNumEndpoints =	0,
+	.bInterfaceClass =	USB_CLASS_AUDIO,
+	.bInterfaceSubClass =	USB_SUBCLASS_AUDIOCONTROL,
+};
+
+DECLARE_USB_AC_HEADER_DESCRIPTOR(2);
+
+#define USB_DT_AC_HEADER_LENGH	USB_DT_AC_HEADER_SIZE(F_AUDIO_NUM_INTERFACES)
+/* B.3.2  Class-Specific AC Interface Descriptor */
+static struct usb_ac_header_descriptor_2 ac_header_desc = {
+	.bLength =		USB_DT_AC_HEADER_LENGH,
+	.bDescriptorType =	USB_DT_CS_INTERFACE,
+	.bDescriptorSubtype =	HEADER,
+	.bcdADC =		__constant_cpu_to_le16(0x0100),
+	.wTotalLength =		__constant_cpu_to_le16(USB_DT_AC_HEADER_LENGH),
+	.bInCollection =	F_AUDIO_NUM_INTERFACES,
+	.baInterfaceNr = {
+		[0] =		F_AUDIO_AC_INTERFACE,
+		[1] =		F_AUDIO_AS_INTERFACE,
+	}
+};
+
+#define INPUT_TERMINAL_ID	1
+static struct usb_input_terminal_descriptor input_terminal_desc = {
+	.bLength =		USB_DT_AC_INPUT_TERMINAL_SIZE,
+	.bDescriptorType =	USB_DT_CS_INTERFACE,
+	.bDescriptorSubtype =	INPUT_TERMINAL,
+	.bTerminalID =		INPUT_TERMINAL_ID,
+	.wTerminalType =	USB_AC_TERMINAL_STREAMING,
+	.bAssocTerminal =	0,
+	.wChannelConfig =	0x3,
+};
+
+DECLARE_USB_AC_FEATURE_UNIT_DESCRIPTOR(0);
+
+#define FEATURE_UNIT_ID		2
+static struct usb_ac_feature_unit_descriptor_0 feature_unit_desc = {
+	.bLength		= USB_DT_AC_FEATURE_UNIT_SIZE(0),
+	.bDescriptorType	= USB_DT_CS_INTERFACE,
+	.bDescriptorSubtype	= FEATURE_UNIT,
+	.bUnitID		= FEATURE_UNIT_ID,
+	.bSourceID		= INPUT_TERMINAL_ID,
+	.bControlSize		= 2,
+	.bmaControls[0]		= (FU_MUTE | FU_VOLUME),
+};
+
+static struct usb_audio_control mute_control = {
+	.list = LIST_HEAD_INIT(mute_control.list),
+	.name = "Mute Control",
+	.type = MUTE_CONTROL,
+	/* Todo: add real Mute control code */
+	.set = generic_set_cmd,
+	.get = generic_get_cmd,
+};
+
+static struct usb_audio_control volume_control = {
+	.list = LIST_HEAD_INIT(volume_control.list),
+	.name = "Volume Control",
+	.type = VOLUME_CONTROL,
+	/* Todo: add real Volume control code */
+	.set = generic_set_cmd,
+	.get = generic_get_cmd,
+};
+
+static struct usb_audio_control_selector feature_unit = {
+	.list = LIST_HEAD_INIT(feature_unit.list),
+	.id = FEATURE_UNIT_ID,
+	.name = "Mute & Volume Control",
+	.type = FEATURE_UNIT,
+	.desc = (struct usb_descriptor_header *)&feature_unit_desc,
+};
+
+#define OUTPUT_TERMINAL_ID	3
+static struct usb_output_terminal_descriptor output_terminal_desc = {
+	.bLength		= USB_DT_AC_OUTPUT_TERMINAL_SIZE,
+	.bDescriptorType	= USB_DT_CS_INTERFACE,
+	.bDescriptorSubtype	= OUTPUT_TERMINAL,
+	.bTerminalID		= OUTPUT_TERMINAL_ID,
+	.wTerminalType		= USB_AC_OUTPUT_TERMINAL_SPEAKER,
+	.bAssocTerminal		= FEATURE_UNIT_ID,
+	.bSourceID		= FEATURE_UNIT_ID,
+};
+
+/* B.4.1  Standard AS Interface Descriptor */
+static struct usb_interface_descriptor as_interface_alt_0_desc = {
+	.bLength =		USB_DT_INTERFACE_SIZE,
+	.bDescriptorType =	USB_DT_INTERFACE,
+	.bAlternateSetting =	0,
+	.bNumEndpoints =	0,
+	.bInterfaceClass =	USB_CLASS_AUDIO,
+	.bInterfaceSubClass =	USB_SUBCLASS_AUDIOSTREAMING,
+};
+
+static struct usb_interface_descriptor as_interface_alt_1_desc = {
+	.bLength =		USB_DT_INTERFACE_SIZE,
+	.bDescriptorType =	USB_DT_INTERFACE,
+	.bAlternateSetting =	1,
+	.bNumEndpoints =	1,
+	.bInterfaceClass =	USB_CLASS_AUDIO,
+	.bInterfaceSubClass =	USB_SUBCLASS_AUDIOSTREAMING,
+};
+
+/* B.4.2  Class-Specific AS Interface Descriptor */
+static struct usb_as_header_descriptor as_header_desc = {
+	.bLength =		USB_DT_AS_HEADER_SIZE,
+	.bDescriptorType =	USB_DT_CS_INTERFACE,
+	.bDescriptorSubtype =	AS_GENERAL,
+	.bTerminalLink =	INPUT_TERMINAL_ID,
+	.bDelay =		1,
+	.wFormatTag =		USB_AS_AUDIO_FORMAT_TYPE_I_PCM,
+};
+
+DECLARE_USB_AS_FORMAT_TYPE_I_DISCRETE_DESC(1);
+
+static struct usb_as_formate_type_i_discrete_descriptor_1 as_type_i_desc = {
+	.bLength =		USB_AS_FORMAT_TYPE_I_DISCRETE_DESC_SIZE(1),
+	.bDescriptorType =	USB_DT_CS_INTERFACE,
+	.bDescriptorSubtype =	FORMAT_TYPE,
+	.bFormatType =		USB_AS_FORMAT_TYPE_I,
+	.bSubframeSize =	2,
+	.bBitResolution =	16,
+	.bSamFreqType =		1,
+};
+
+/* Standard ISO OUT Endpoint Descriptor */
+static struct usb_endpoint_descriptor as_out_ep_desc __initdata = {
+	.bLength =		USB_DT_ENDPOINT_AUDIO_SIZE,
+	.bDescriptorType =	USB_DT_ENDPOINT,
+	.bEndpointAddress =	USB_DIR_OUT,
+	.bmAttributes =		USB_AS_ENDPOINT_ADAPTIVE
+				| USB_ENDPOINT_XFER_ISOC,
+	.wMaxPacketSize =	__constant_cpu_to_le16(OUT_EP_MAX_PACKET_SIZE),
+	.bInterval =		4,
+};
+
+/* Class-specific AS ISO OUT Endpoint Descriptor */
+static struct usb_as_iso_endpoint_descriptor as_iso_out_desc __initdata = {
+	.bLength =		USB_AS_ISO_ENDPOINT_DESC_SIZE,
+	.bDescriptorType =	USB_DT_CS_ENDPOINT,
+	.bDescriptorSubtype =	EP_GENERAL,
+	.bmAttributes = 	1,
+	.bLockDelayUnits =	1,
+	.wLockDelay =		__constant_cpu_to_le16(1),
+};
+
+static struct usb_descriptor_header *f_audio_desc[] __initdata = {
+	(struct usb_descriptor_header *)&ac_interface_desc,
+	(struct usb_descriptor_header *)&ac_header_desc,
+
+	(struct usb_descriptor_header *)&input_terminal_desc,
+	(struct usb_descriptor_header *)&output_terminal_desc,
+	(struct usb_descriptor_header *)&feature_unit_desc,
+
+	(struct usb_descriptor_header *)&as_interface_alt_0_desc,
+	(struct usb_descriptor_header *)&as_interface_alt_1_desc,
+	(struct usb_descriptor_header *)&as_header_desc,
+
+	(struct usb_descriptor_header *)&as_type_i_desc,
+
+	(struct usb_descriptor_header *)&as_out_ep_desc,
+	(struct usb_descriptor_header *)&as_iso_out_desc,
+	NULL,
+};
+
+/* string IDs are assigned dynamically */
+
+#define STRING_MANUFACTURER_IDX		0
+#define STRING_PRODUCT_IDX		1
+
+static char manufacturer[50];
+
+static struct usb_string strings_dev[] = {
+	[STRING_MANUFACTURER_IDX].s = manufacturer,
+	[STRING_PRODUCT_IDX].s = DRIVER_DESC,
+	{  } /* end of list */
+};
+
+static struct usb_gadget_strings stringtab_dev = {
+	.language	= 0x0409,	/* en-us */
+	.strings	= strings_dev,
+};
+
+static struct usb_gadget_strings *audio_strings[] = {
+	&stringtab_dev,
+	NULL,
+};
+
+/*
+ * This function is an ALSA sound card following USB Audio Class Spec 1.0.
+ */
+
+/*-------------------------------------------------------------------------*/
+struct f_audio_buf {
+	u8 *buf;
+	int actual;
+	struct list_head list;
+};
+
+static struct f_audio_buf *f_audio_buffer_alloc(int buf_size)
+{
+	struct f_audio_buf *copy_buf;
+
+	copy_buf = kzalloc(sizeof *copy_buf, GFP_ATOMIC);
+	if (!copy_buf)
+		return (struct f_audio_buf *)-ENOMEM;
+
+	copy_buf->buf = kzalloc(buf_size, GFP_ATOMIC);
+	if (!copy_buf->buf) {
+		kfree(copy_buf);
+		return (struct f_audio_buf *)-ENOMEM;
+	}
+
+	return copy_buf;
+}
+
+static void f_audio_buffer_free(struct f_audio_buf *audio_buf)
+{
+	kfree(audio_buf->buf);
+	kfree(audio_buf);
+}
+/*-------------------------------------------------------------------------*/
+
+struct f_audio {
+	struct gaudio			card;
+
+	/* endpoints handle full and/or high speeds */
+	struct usb_ep			*out_ep;
+	struct usb_endpoint_descriptor	*out_desc;
+
+	spinlock_t			lock;
+	struct f_audio_buf *copy_buf;
+	struct work_struct playback_work;
+	struct list_head play_queue;
+
+	/* Control Set command */
+	struct list_head cs;
+	u8 set_cmd;
+	struct usb_audio_control *set_con;
+};
+
+static inline struct f_audio *func_to_audio(struct usb_function *f)
+{
+	return container_of(f, struct f_audio, card.func);
+}
+
+/*-------------------------------------------------------------------------*/
+
+static void f_audio_playback_work(struct work_struct *data)
+{
+	struct f_audio *audio = container_of(data, struct f_audio,
+					playback_work);
+	struct f_audio_buf *play_buf;
+
+	spin_lock_irq(&audio->lock);
+	if (list_empty(&audio->play_queue)) {
+		spin_unlock_irq(&audio->lock);
+		return;
+	}
+	play_buf = list_first_entry(&audio->play_queue,
+			struct f_audio_buf, list);
+	list_del(&play_buf->list);
+	spin_unlock_irq(&audio->lock);
+
+	u_audio_playback(&audio->card, play_buf->buf, play_buf->actual);
+	f_audio_buffer_free(play_buf);
+
+	return;
+}
+
+static int f_audio_out_ep_complete(struct usb_ep *ep, struct usb_request *req)
+{
+	struct f_audio *audio = req->context;
+	struct usb_composite_dev *cdev = audio->card.func.config->cdev;
+	struct f_audio_buf *copy_buf = audio->copy_buf;
+	int err;
+
+	if (!copy_buf)
+		return -EINVAL;
+
+	/* Copy buffer is full, add it to the play_queue */
+	if (audio_buf_size - copy_buf->actual < req->actual) {
+		list_add_tail(&copy_buf->list, &audio->play_queue);
+		schedule_work(&audio->playback_work);
+		copy_buf = f_audio_buffer_alloc(audio_buf_size);
+		if (copy_buf < 0)
+			return -ENOMEM;
+	}
+
+	memcpy(copy_buf->buf + copy_buf->actual, req->buf, req->actual);
+	copy_buf->actual += req->actual;
+	audio->copy_buf = copy_buf;
+
+	err = usb_ep_queue(ep, req, GFP_ATOMIC);
+	if (err)
+		ERROR(cdev, "%s queue req: %d\n", ep->name, err);
+
+	return 0;
+
+}
+
+static void f_audio_complete(struct usb_ep *ep, struct usb_request *req)
+{
+	struct f_audio *audio = req->context;
+	int status = req->status;
+	u32 data = 0;
+	struct usb_ep *out_ep = audio->out_ep;
+
+	switch (status) {
+
+	case 0:				/* normal completion? */
+		if (ep == out_ep)
+			f_audio_out_ep_complete(ep, req);
+		else if (audio->set_con) {
+			memcpy(&data, req->buf, req->length);
+			audio->set_con->set(audio->set_con, audio->set_cmd,
+					le16_to_cpu(data));
+			audio->set_con = NULL;
+		}
+		break;
+	default:
+		break;
+	}
+}
+
+static int audio_set_intf_req(struct usb_function *f,
+		const struct usb_ctrlrequest *ctrl)
+{
+	struct f_audio		*audio = func_to_audio(f);
+	struct usb_composite_dev *cdev = f->config->cdev;
+	struct usb_request	*req = cdev->req;
+	u8			id = ((le16_to_cpu(ctrl->wIndex) >> 8) & 0xFF);
+	u16			len = le16_to_cpu(ctrl->wLength);
+	u16			w_value = le16_to_cpu(ctrl->wValue);
+	u8			con_sel = (w_value >> 8) & 0xFF;
+	u8			cmd = (ctrl->bRequest & 0x0F);
+	struct usb_audio_control_selector *cs;
+	struct usb_audio_control *con;
+
+	DBG(cdev, "bRequest 0x%x, w_value 0x%04x, len %d, entity %d\n",
+			ctrl->bRequest, w_value, len, id);
+
+	list_for_each_entry(cs, &audio->cs, list) {
+		if (cs->id == id) {
+			list_for_each_entry(con, &cs->control, list) {
+				if (con->type == con_sel) {
+					audio->set_con = con;
+					break;
+				}
+			}
+			break;
+		}
+	}
+
+	audio->set_cmd = cmd;
+	req->context = audio;
+	req->complete = f_audio_complete;
+
+	return len;
+}
+
+static int audio_get_intf_req(struct usb_function *f,
+		const struct usb_ctrlrequest *ctrl)
+{
+	struct f_audio		*audio = func_to_audio(f);
+	struct usb_composite_dev *cdev = f->config->cdev;
+	struct usb_request	*req = cdev->req;
+	int			value = -EOPNOTSUPP;
+	u8			id = ((le16_to_cpu(ctrl->wIndex) >> 8) & 0xFF);
+	u16			len = le16_to_cpu(ctrl->wLength);
+	u16			w_value = le16_to_cpu(ctrl->wValue);
+	u8			con_sel = (w_value >> 8) & 0xFF;
+	u8			cmd = (ctrl->bRequest & 0x0F);
+	struct usb_audio_control_selector *cs;
+	struct usb_audio_control *con;
+
+	DBG(cdev, "bRequest 0x%x, w_value 0x%04x, len %d, entity %d\n",
+			ctrl->bRequest, w_value, len, id);
+
+	list_for_each_entry(cs, &audio->cs, list) {
+		if (cs->id == id) {
+			list_for_each_entry(con, &cs->control, list) {
+				if (con->type == con_sel && con->get) {
+					value = con->get(con, cmd);
+					break;
+				}
+			}
+			break;
+		}
+	}
+
+	req->context = audio;
+	req->complete = f_audio_complete;
+	memcpy(req->buf, &value, len);
+
+	return len;
+}
+
+static int
+f_audio_setup(struct usb_function *f, const struct usb_ctrlrequest *ctrl)
+{
+	struct usb_composite_dev *cdev = f->config->cdev;
+	struct usb_request	*req = cdev->req;
+	int			value = -EOPNOTSUPP;
+	u16			w_index = le16_to_cpu(ctrl->wIndex);
+	u16			w_value = le16_to_cpu(ctrl->wValue);
+	u16			w_length = le16_to_cpu(ctrl->wLength);
+
+	/* composite driver infrastructure handles everything except
+	 * Audio class messages; interface activation uses set_alt().
+	 */
+	switch (ctrl->bRequestType) {
+	case USB_AUDIO_SET_INTF:
+		value = audio_set_intf_req(f, ctrl);
+		break;
+
+	case USB_AUDIO_GET_INTF:
+		value = audio_get_intf_req(f, ctrl);
+		break;
+
+	default:
+		ERROR(cdev, "invalid control req%02x.%02x v%04x i%04x l%d\n",
+			ctrl->bRequestType, ctrl->bRequest,
+			w_value, w_index, w_length);
+	}
+
+	/* respond with data transfer or status phase? */
+	if (value >= 0) {
+		DBG(cdev, "audio req%02x.%02x v%04x i%04x l%d\n",
+			ctrl->bRequestType, ctrl->bRequest,
+			w_value, w_index, w_length);
+		req->zero = 0;
+		req->length = value;
+		value = usb_ep_queue(cdev->gadget->ep0, req, GFP_ATOMIC);
+		if (value < 0)
+			ERROR(cdev, "audio response on err %d\n", value);
+	}
+
+	/* device either stalls (value < 0) or reports success */
+	return value;
+}
+
+static int f_audio_set_alt(struct usb_function *f, unsigned intf, unsigned alt)
+{
+	struct f_audio		*audio = func_to_audio(f);
+	struct usb_composite_dev *cdev = f->config->cdev;
+	struct usb_ep *out_ep = audio->out_ep;
+	struct usb_request *req;
+	int i = 0, err = 0;
+
+	DBG(cdev, "intf %d, alt %d\n", intf, alt);
+
+	if (intf == 1) {
+		if (alt == 1) {
+			usb_ep_enable(out_ep, audio->out_desc);
+			out_ep->driver_data = audio;
+			audio->copy_buf = f_audio_buffer_alloc(audio_buf_size);
+
+			/*
+			 * allocate a bunch of read buffers
+			 * and queue them all at once.
+			 */
+			for (i = 0; i < req_count && err == 0; i++) {
+				req = usb_ep_alloc_request(out_ep, GFP_ATOMIC);
+				if (req) {
+					req->buf = kzalloc(req_buf_size,
+							GFP_ATOMIC);
+					if (req->buf) {
+						req->length = req_buf_size;
+						req->context = audio;
+						req->complete =
+							f_audio_complete;
+						err = usb_ep_queue(out_ep,
+							req, GFP_ATOMIC);
+						if (err)
+							ERROR(cdev,
+							"%s queue req: %d\n",
+							out_ep->name, err);
+					} else
+						err = -ENOMEM;
+				} else
+					err = -ENOMEM;
+			}
+
+		} else {
+			struct f_audio_buf *copy_buf = audio->copy_buf;
+			if (copy_buf) {
+				list_add_tail(&copy_buf->list,
+						&audio->play_queue);
+				schedule_work(&audio->playback_work);
+			}
+		}
+	}
+
+	return err;
+}
+
+static void f_audio_disable(struct usb_function *f)
+{
+	return;
+}
+
+/*-------------------------------------------------------------------------*/
+
+static void f_audio_build_desc(struct f_audio *audio)
+{
+	struct gaudio *card = &audio->card;
+	u8 *sam_freq;
+	int rate;
+
+	/* Set channel numbers */
+	input_terminal_desc.bNrChannels = u_audio_get_playback_channels(card);
+	as_type_i_desc.bNrChannels = u_audio_get_playback_channels(card);
+
+	/* Set sample rates */
+	rate = u_audio_get_playback_rate(card);
+	sam_freq = as_type_i_desc.tSamFreq[0];
+	memcpy(sam_freq, &rate, 3);
+
+	/* Todo: Set Sample bits and other parameters */
+
+	return;
+}
+
+/* audio function driver setup/binding */
+static int __init
+f_audio_bind(struct usb_configuration *c, struct usb_function *f)
+{
+	struct usb_composite_dev *cdev = c->cdev;
+	struct f_audio		*audio = func_to_audio(f);
+	int			status;
+	struct usb_ep		*ep;
+
+	f_audio_build_desc(audio);
+
+	/* allocate instance-specific interface IDs, and patch descriptors */
+	status = usb_interface_id(c, f);
+	if (status < 0)
+		goto fail;
+	ac_interface_desc.bInterfaceNumber = status;
+
+	status = usb_interface_id(c, f);
+	if (status < 0)
+		goto fail;
+	as_interface_alt_0_desc.bInterfaceNumber = status;
+	as_interface_alt_1_desc.bInterfaceNumber = status;
+
+	status = -ENODEV;
+
+	/* allocate instance-specific endpoints */
+	ep = usb_ep_autoconfig(cdev->gadget, &as_out_ep_desc);
+	if (!ep)
+		goto fail;
+	audio->out_ep = ep;
+	ep->driver_data = cdev;	/* claim */
+
+	status = -ENOMEM;
+
+	/* supcard all relevant hardware speeds... we expect that when
+	 * hardware is dual speed, all bulk-capable endpoints work at
+	 * both speeds
+	 */
+
+	/* copy descriptors, and track endpoint copies */
+	if (gadget_is_dualspeed(c->cdev->gadget)) {
+		c->highspeed = true;
+		f->hs_descriptors = usb_copy_descriptors(f_audio_desc);
+	} else
+		f->descriptors = usb_copy_descriptors(f_audio_desc);
+
+	return 0;
+
+fail:
+
+	return status;
+}
+
+static void
+f_audio_unbind(struct usb_configuration *c, struct usb_function *f)
+{
+	struct f_audio		*audio = func_to_audio(f);
+
+	usb_free_descriptors(f->descriptors);
+	kfree(audio);
+}
+
+/*-------------------------------------------------------------------------*/
+
+/* Todo: add more control selecotor dynamically */
+int __init control_selector_init(struct f_audio *audio)
+{
+	INIT_LIST_HEAD(&audio->cs);
+	list_add(&feature_unit.list, &audio->cs);
+
+	INIT_LIST_HEAD(&feature_unit.control);
+	list_add(&mute_control.list, &feature_unit.control);
+	list_add(&volume_control.list, &feature_unit.control);
+
+	volume_control.data[_CUR] = 0xffc0;
+	volume_control.data[_MIN] = 0xe3a0;
+	volume_control.data[_MAX] = 0xfff0;
+	volume_control.data[_RES] = 0x0030;
+
+	return 0;
+}
+
+/**
+ * audio_bind_config - add USB audio fucntion to a configuration
+ * @c: the configuration to supcard the USB audio function
+ * Context: single threaded during gadget setup
+ *
+ * Returns zero on success, else negative errno.
+ */
+int __init audio_bind_config(struct usb_configuration *c)
+{
+	struct f_audio *audio;
+	int status;
+
+	/* allocate and initialize one new instance */
+	audio = kzalloc(sizeof *audio, GFP_KERNEL);
+	if (!audio)
+		return -ENOMEM;
+
+	audio->card.func.name = "g_audio";
+	audio->card.gadget = c->cdev->gadget;
+
+	INIT_LIST_HEAD(&audio->play_queue);
+	spin_lock_init(&audio->lock);
+
+	/* set up ASLA audio devices */
+	status = gaudio_setup(&audio->card);
+	if (status < 0)
+		goto setup_fail;
+
+	audio->card.func.strings = audio_strings;
+	audio->card.func.bind = f_audio_bind;
+	audio->card.func.unbind = f_audio_unbind;
+	audio->card.func.set_alt = f_audio_set_alt;
+	audio->card.func.setup = f_audio_setup;
+	audio->card.func.disable = f_audio_disable;
+	audio->out_desc = &as_out_ep_desc;
+
+	control_selector_init(audio);
+
+	INIT_WORK(&audio->playback_work, f_audio_playback_work);
+
+	status = usb_add_function(c, &audio->card.func);
+	if (status)
+		goto add_fail;
+
+	INFO(c->cdev, "audio_buf_size %d, req_buf_size %d, req_count %d\n",
+		audio_buf_size, req_buf_size, req_count);
+
+	return status;
+
+add_fail:
+	gaudio_cleanup(&audio->card);
+setup_fail:
+	kfree(audio);
+	return status;
+}
diff --git a/drivers/usb/gadget/u_audio.c b/drivers/usb/gadget/u_audio.c
new file mode 100644
index 0000000..0f3d22f
--- /dev/null
+++ b/drivers/usb/gadget/u_audio.c
@@ -0,0 +1,319 @@
+/*
+ * u_audio.c -- ALSA audio utilities for Gadget stack
+ *
+ * Copyright (C) 2008 Bryan Wu <cooloney@kernel.org>
+ * Copyright (C) 2008 Analog Devices, Inc
+ *
+ * Enter bugs at http://blackfin.uclinux.org/
+ *
+ * Licensed under the GPL-2 or later.
+ */
+
+#include <linux/kernel.h>
+#include <linux/utsname.h>
+#include <linux/device.h>
+#include <linux/delay.h>
+#include <linux/ctype.h>
+#include <linux/random.h>
+#include <linux/syscalls.h>
+
+#include "u_audio.h"
+
+/*
+ * This component encapsulates the ALSA devices for USB audio gadget
+ */
+
+#define FILE_PCM_PLAYBACK	"/dev/snd/pcmC0D0p"
+#define FILE_PCM_CAPTURE	"/dev/snd/pcmC0D0c"
+#define FILE_CONTROL		"/dev/snd/controlC0"
+
+static char *fn_play = FILE_PCM_PLAYBACK;
+module_param(fn_play, charp, S_IRUGO);
+MODULE_PARM_DESC(fn_play, "Playback PCM device file name");
+
+static char *fn_cap = FILE_PCM_CAPTURE;
+module_param(fn_cap, charp, S_IRUGO);
+MODULE_PARM_DESC(fn_cap, "Capture PCM device file name");
+
+static char *fn_cntl = FILE_CONTROL;
+module_param(fn_cntl, charp, S_IRUGO);
+MODULE_PARM_DESC(fn_cntl, "Control device file name");
+
+/*-------------------------------------------------------------------------*/
+
+/**
+ * Some ALSA internal helper functions
+ */
+static int snd_interval_refine_set(struct snd_interval *i, unsigned int val)
+{
+	struct snd_interval t;
+	t.empty = 0;
+	t.min = t.max = val;
+	t.openmin = t.openmax = 0;
+	t.integer = 1;
+	return snd_interval_refine(i, &t);
+}
+
+static int _snd_pcm_hw_param_set(struct snd_pcm_hw_params *params,
+				 snd_pcm_hw_param_t var, unsigned int val,
+				 int dir)
+{
+	int changed;
+	if (hw_is_mask(var)) {
+		struct snd_mask *m = hw_param_mask(params, var);
+		if (val == 0 && dir < 0) {
+			changed = -EINVAL;
+			snd_mask_none(m);
+		} else {
+			if (dir > 0)
+				val++;
+			else if (dir < 0)
+				val--;
+			changed = snd_mask_refine_set(
+					hw_param_mask(params, var), val);
+		}
+	} else if (hw_is_interval(var)) {
+		struct snd_interval *i = hw_param_interval(params, var);
+		if (val == 0 && dir < 0) {
+			changed = -EINVAL;
+			snd_interval_none(i);
+		} else if (dir == 0)
+			changed = snd_interval_refine_set(i, val);
+		else {
+			struct snd_interval t;
+			t.openmin = 1;
+			t.openmax = 1;
+			t.empty = 0;
+			t.integer = 0;
+			if (dir < 0) {
+				t.min = val - 1;
+				t.max = val;
+			} else {
+				t.min = val;
+				t.max = val+1;
+			}
+			changed = snd_interval_refine(i, &t);
+		}
+	} else
+		return -EINVAL;
+	if (changed) {
+		params->cmask |= 1 << var;
+		params->rmask |= 1 << var;
+	}
+	return changed;
+}
+/*-------------------------------------------------------------------------*/
+
+/**
+ * Set default hardware params
+ */
+static int playback_default_hw_params(struct gaudio_snd_dev *snd)
+{
+	struct snd_pcm_substream *substream = snd->substream;
+	struct snd_pcm_hw_params *params;
+	snd_pcm_sframes_t result;
+
+       /*
+	* SNDRV_PCM_ACCESS_RW_INTERLEAVED,
+	* SNDRV_PCM_FORMAT_S16_LE
+	* CHANNELS: 2
+	* RATE: 48000
+	*/
+	snd->access = SNDRV_PCM_ACCESS_RW_INTERLEAVED;
+	snd->format = SNDRV_PCM_FORMAT_S16_LE;
+	snd->channels = 2;
+	snd->rate = 48000;
+
+	params = kzalloc(sizeof(*params), GFP_KERNEL);
+	if (!params)
+		return -ENOMEM;
+
+	_snd_pcm_hw_params_any(params);
+	_snd_pcm_hw_param_set(params, SNDRV_PCM_HW_PARAM_ACCESS,
+			snd->access, 0);
+	_snd_pcm_hw_param_set(params, SNDRV_PCM_HW_PARAM_FORMAT,
+			snd->format, 0);
+	_snd_pcm_hw_param_set(params, SNDRV_PCM_HW_PARAM_CHANNELS,
+			snd->channels, 0);
+	_snd_pcm_hw_param_set(params, SNDRV_PCM_HW_PARAM_RATE,
+			snd->rate, 0);
+
+	snd_pcm_kernel_ioctl(substream, SNDRV_PCM_IOCTL_DROP, NULL);
+	snd_pcm_kernel_ioctl(substream, SNDRV_PCM_IOCTL_HW_PARAMS, params);
+
+	result = snd_pcm_kernel_ioctl(substream, SNDRV_PCM_IOCTL_PREPARE, NULL);
+	if (result < 0) {
+		ERROR(snd->card,
+			"Preparing sound card failed: %d\n", (int)result);
+		kfree(params);
+		return result;
+	}
+
+	/* Store the hardware parameters */
+	snd->access = params_access(params);
+	snd->format = params_format(params);
+	snd->channels = params_channels(params);
+	snd->rate = params_rate(params);
+
+	kfree(params);
+
+	INFO(snd->card,
+		"Hardware params: access %x, format %x, channels %d, rate %d\n",
+		snd->access, snd->format, snd->channels, snd->rate);
+
+	return 0;
+}
+
+/**
+ * Playback audio buffer data by ALSA PCM device
+ */
+static size_t u_audio_playback(struct gaudio *card, void *buf, size_t count)
+{
+	struct gaudio_snd_dev	*snd = &card->playback;
+	struct snd_pcm_substream *substream = snd->substream;
+	struct snd_pcm_runtime *runtime = substream->runtime;
+	mm_segment_t old_fs;
+	ssize_t result;
+	snd_pcm_sframes_t frames;
+
+try_again:
+	if (runtime->status->state == SNDRV_PCM_STATE_XRUN ||
+		runtime->status->state == SNDRV_PCM_STATE_SUSPENDED) {
+		result = snd_pcm_kernel_ioctl(substream,
+				SNDRV_PCM_IOCTL_PREPARE, NULL);
+		if (result < 0) {
+			ERROR(card, "Preparing sound card failed: %d\n",
+					(int)result);
+			return result;
+		}
+	}
+
+	frames = bytes_to_frames(runtime, count);
+	old_fs = get_fs();
+	set_fs(KERNEL_DS);
+	result = snd_pcm_lib_write(snd->substream, buf, frames);
+	if (result != frames) {
+		ERROR(card, "Playback error: %d\n", (int)result);
+		set_fs(old_fs);
+		goto try_again;
+	}
+	set_fs(old_fs);
+
+	return 0;
+}
+
+static int u_audio_get_playback_channels(struct gaudio *card)
+{
+	return card->playback.channels;
+}
+
+static int u_audio_get_playback_rate(struct gaudio *card)
+{
+	return card->playback.rate;
+}
+
+/**
+ * Open ALSA PCM and control device files
+ * Initial the PCM or control device
+ */
+static int gaudio_open_snd_dev(struct gaudio *card)
+{
+	struct snd_pcm_file *pcm_file;
+	struct gaudio_snd_dev *snd;
+
+	if (!card)
+		return -ENODEV;
+
+	/* Open control device */
+	snd = &card->control;
+	snd->filp = filp_open(fn_cntl, O_RDWR, 0);
+	if (IS_ERR(snd->filp)) {
+		int ret = PTR_ERR(snd->filp);
+		ERROR(card, "unable to open sound control device file: %s\n",
+				fn_cntl);
+		snd->filp = NULL;
+		return ret;
+	}
+	snd->card = card;
+
+	/* Open PCM playback device and setup substream */
+	snd = &card->playback;
+	snd->filp = filp_open(fn_play, O_WRONLY, 0);
+	if (IS_ERR(snd->filp)) {
+		ERROR(card, "No such PCM playback device: %s\n", fn_play);
+		snd->filp = NULL;
+	}
+	pcm_file = snd->filp->private_data;
+	snd->substream = pcm_file->substream;
+	snd->card = card;
+	playback_default_hw_params(snd);
+
+	/* Open PCM capture device and setup substream */
+	snd = &card->capture;
+	snd->filp = filp_open(fn_cap, O_RDONLY, 0);
+	if (IS_ERR(snd->filp)) {
+		ERROR(card, "No such PCM capture device: %s\n", fn_cap);
+		snd->filp = NULL;
+	}
+	pcm_file = snd->filp->private_data;
+	snd->substream = pcm_file->substream;
+	snd->card = card;
+
+	return 0;
+}
+
+/**
+ * Close ALSA PCM and control device files
+ */
+static int gaudio_close_snd_dev(struct gaudio *gau)
+{
+	struct gaudio_snd_dev	*snd;
+
+	/* Close control device */
+	snd = &gau->control;
+	if (!IS_ERR(snd->filp))
+		filp_close(snd->filp, current->files);
+
+	/* Close PCM playback device and setup substream */
+	snd = &gau->playback;
+	if (!IS_ERR(snd->filp))
+		filp_close(snd->filp, current->files);
+
+	/* Close PCM capture device and setup substream */
+	snd = &gau->capture;
+	if (!IS_ERR(snd->filp))
+		filp_close(snd->filp, current->files);
+
+	return 0;
+}
+
+/**
+ * gaudio_setup - setup ALSA interface and preparing for USB transfer
+ *
+ * This sets up PCM, mixer or MIDI ALSA devices fore USB gadget using.
+ *
+ * Returns negative errno, or zero on success
+ */
+int __init gaudio_setup(struct gaudio *card)
+{
+	int	ret;
+
+	ret = gaudio_open_snd_dev(card);
+	if (ret)
+		ERROR(card, "we need at least one control device\n");
+
+	return ret;
+
+}
+
+/**
+ * gaudio_cleanup - remove ALSA device interface
+ *
+ * This is called to free all resources allocated by @gaudio_setup().
+ */
+void gaudio_cleanup(struct gaudio *card)
+{
+	if (card)
+		gaudio_close_snd_dev(card);
+}
+
diff --git a/drivers/usb/gadget/u_audio.h b/drivers/usb/gadget/u_audio.h
new file mode 100644
index 0000000..cc8d159
--- /dev/null
+++ b/drivers/usb/gadget/u_audio.h
@@ -0,0 +1,56 @@
+/*
+ * u_audio.h -- interface to USB gadget "ALSA AUDIO" utilities
+ *
+ * Copyright (C) 2008 Bryan Wu <cooloney@kernel.org>
+ * Copyright (C) 2008 Analog Devices, Inc
+ *
+ * Enter bugs at http://blackfin.uclinux.org/
+ *
+ * Licensed under the GPL-2 or later.
+ */
+
+#ifndef __U_AUDIO_H
+#define __U_AUDIO_H
+
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/usb/audio.h>
+#include <linux/usb/composite.h>
+
+#include <sound/core.h>
+#include <sound/pcm.h>
+#include <sound/pcm_params.h>
+
+#include "gadget_chips.h"
+
+/*
+ * This represents the USB side of an audio card device, managed by a USB
+ * function which provides control and stream interfaces.
+ */
+
+struct gaudio_snd_dev {
+	struct gaudio			*card;
+	struct file			*filp;
+	struct snd_pcm_substream	*substream;
+	int				access;
+	int				format;
+	int				channels;
+	int				rate;
+};
+
+struct gaudio {
+	struct usb_function		func;
+	struct usb_gadget		*gadget;
+
+	/* ALSA sound device interfaces */
+	struct gaudio_snd_dev		control;
+	struct gaudio_snd_dev		playback;
+	struct gaudio_snd_dev		capture;
+
+	/* TODO */
+};
+
+int gaudio_setup(struct gaudio *card);
+void gaudio_cleanup(struct gaudio *card);
+
+#endif /* __U_AUDIO_H */