usb: gadget: accessory: Add Android Accessory function

USB accessory mode allows users to connect USB host hardware
specifically designed for Android-powered devices. The accessories
must adhere to the Android accessory protocol outlined in the
http://accessories.android.com documentation. This allows
Android devices that cannot act as a USB host to still interact with
USB hardware. When an Android device is in USB accessory mode, the
attached Android USB accessory acts as the host, provides power
to the USB bus, and enumerates connected devices.

Signed-off-by: Mike Lockwood <lockwood@android.com>

3 files changed, 924 insertions, 0 deletions

diff --git a/drivers/usb/gadget/android.c b/drivers/usb/gadget/android.c
index b9cb65d..b39ae67 100644
--- a/drivers/usb/gadget/android.c
+++ b/drivers/usb/gadget/android.c
@@ -47,6 +47,7 @@
 #include "f_acm.c"
 #include "f_adb.c"
 #include "f_mtp.c"
+#include "f_accessory.c"
 #define USB_ETH_RNDIS y
 #include "f_rndis.c"
 #include "rndis.c"
@@ -633,6 +634,39 @@ static struct android_usb_function mass_storage_function = {
 };
 
 
+static int accessory_function_init(struct android_usb_function *f,
+					struct usb_composite_dev *cdev)
+{
+	return acc_setup();
+}
+
+static void accessory_function_cleanup(struct android_usb_function *f)
+{
+	acc_cleanup();
+}
+
+static int accessory_function_bind_config(struct android_usb_function *f,
+						struct usb_configuration *c)
+{
+	return acc_bind_config(c);
+}
+
+static int accessory_function_ctrlrequest(struct android_usb_function *f,
+						struct usb_composite_dev *cdev,
+						const struct usb_ctrlrequest *c)
+{
+	return acc_ctrlrequest(cdev, c);
+}
+
+static struct android_usb_function accessory_function = {
+	.name		= "accessory",
+	.init		= accessory_function_init,
+	.cleanup	= accessory_function_cleanup,
+	.bind_config	= accessory_function_bind_config,
+	.ctrlrequest	= accessory_function_ctrlrequest,
+};
+
+
 static struct android_usb_function *supported_functions[] = {
 	&adb_function,
 	&acm_function,
@@ -640,6 +674,7 @@ static struct android_usb_function *supported_functions[] = {
 	&ptp_function,
 	&rndis_function,
 	&mass_storage_function,
+	&accessory_function,
 	NULL
 };
 
@@ -825,6 +860,10 @@ static ssize_t enable_store(struct device *pdev, struct device_attribute *attr,
 	struct usb_composite_dev *cdev = dev->cdev;
 	int enabled = 0;
 
+
+	if (!cdev)
+		return -ENODEV;
+
 	mutex_lock(&dev->mutex);
 
 	sscanf(buff, "%d", &enabled);
@@ -1072,6 +1111,12 @@ android_setup(struct usb_gadget *gadget, const struct usb_ctrlrequest *c)
 		}
 	}
 
+	/* Special case the accessory function.
+	 * It needs to handle control requests before it is enabled.
+	 */
+	if (value < 0)
+		value = acc_ctrlrequest(cdev, c);
+
 	if (value < 0)
 		value = composite_setup(gadget, c);
 
diff --git a/drivers/usb/gadget/f_accessory.c b/drivers/usb/gadget/f_accessory.c
new file mode 100644
index 0000000..a581822
--- /dev/null
+++ b/drivers/usb/gadget/f_accessory.c
@@ -0,0 +1,796 @@
+/*
+ * Gadget Function Driver for Android USB accessories
+ *
+ * Copyright (C) 2011 Google, Inc.
+ * Author: Mike Lockwood <lockwood@android.com>
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+/* #define DEBUG */
+/* #define VERBOSE_DEBUG */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/poll.h>
+#include <linux/delay.h>
+#include <linux/wait.h>
+#include <linux/err.h>
+#include <linux/interrupt.h>
+#include <linux/kthread.h>
+#include <linux/freezer.h>
+
+#include <linux/types.h>
+#include <linux/file.h>
+#include <linux/device.h>
+#include <linux/miscdevice.h>
+
+#include <linux/usb.h>
+#include <linux/usb/ch9.h>
+#include <linux/usb/f_accessory.h>
+
+#define BULK_BUFFER_SIZE    16384
+#define ACC_STRING_SIZE     256
+
+#define PROTOCOL_VERSION    1
+
+/* String IDs */
+#define INTERFACE_STRING_INDEX	0
+
+/* number of tx and rx requests to allocate */
+#define TX_REQ_MAX 4
+#define RX_REQ_MAX 2
+
+struct acc_dev {
+	struct usb_function function;
+	struct usb_composite_dev *cdev;
+	spinlock_t lock;
+
+	struct usb_ep *ep_in;
+	struct usb_ep *ep_out;
+
+	/* set to 1 when we connect */
+	int online:1;
+	/* Set to 1 when we disconnect.
+	 * Not cleared until our file is closed.
+	 */
+	int disconnected:1;
+
+	/* strings sent by the host */
+	char manufacturer[ACC_STRING_SIZE];
+	char model[ACC_STRING_SIZE];
+	char description[ACC_STRING_SIZE];
+	char version[ACC_STRING_SIZE];
+	char uri[ACC_STRING_SIZE];
+	char serial[ACC_STRING_SIZE];
+
+	/* for acc_complete_set_string */
+	int string_index;
+
+	/* set to 1 if we have a pending start request */
+	int start_requested;
+
+	/* synchronize access to our device file */
+	atomic_t open_excl;
+
+	struct list_head tx_idle;
+
+	wait_queue_head_t read_wq;
+	wait_queue_head_t write_wq;
+	struct usb_request *rx_req[RX_REQ_MAX];
+	int rx_done;
+	struct delayed_work work;
+};
+
+static struct usb_interface_descriptor acc_interface_desc = {
+	.bLength                = USB_DT_INTERFACE_SIZE,
+	.bDescriptorType        = USB_DT_INTERFACE,
+	.bInterfaceNumber       = 0,
+	.bNumEndpoints          = 2,
+	.bInterfaceClass        = USB_CLASS_VENDOR_SPEC,
+	.bInterfaceSubClass     = USB_SUBCLASS_VENDOR_SPEC,
+	.bInterfaceProtocol     = 0,
+};
+
+static struct usb_endpoint_descriptor acc_highspeed_in_desc = {
+	.bLength                = USB_DT_ENDPOINT_SIZE,
+	.bDescriptorType        = USB_DT_ENDPOINT,
+	.bEndpointAddress       = USB_DIR_IN,
+	.bmAttributes           = USB_ENDPOINT_XFER_BULK,
+	.wMaxPacketSize         = __constant_cpu_to_le16(512),
+};
+
+static struct usb_endpoint_descriptor acc_highspeed_out_desc = {
+	.bLength                = USB_DT_ENDPOINT_SIZE,
+	.bDescriptorType        = USB_DT_ENDPOINT,
+	.bEndpointAddress       = USB_DIR_OUT,
+	.bmAttributes           = USB_ENDPOINT_XFER_BULK,
+	.wMaxPacketSize         = __constant_cpu_to_le16(512),
+};
+
+static struct usb_endpoint_descriptor acc_fullspeed_in_desc = {
+	.bLength                = USB_DT_ENDPOINT_SIZE,
+	.bDescriptorType        = USB_DT_ENDPOINT,
+	.bEndpointAddress       = USB_DIR_IN,
+	.bmAttributes           = USB_ENDPOINT_XFER_BULK,
+};
+
+static struct usb_endpoint_descriptor acc_fullspeed_out_desc = {
+	.bLength                = USB_DT_ENDPOINT_SIZE,
+	.bDescriptorType        = USB_DT_ENDPOINT,
+	.bEndpointAddress       = USB_DIR_OUT,
+	.bmAttributes           = USB_ENDPOINT_XFER_BULK,
+};
+
+static struct usb_descriptor_header *fs_acc_descs[] = {
+	(struct usb_descriptor_header *) &acc_interface_desc,
+	(struct usb_descriptor_header *) &acc_fullspeed_in_desc,
+	(struct usb_descriptor_header *) &acc_fullspeed_out_desc,
+	NULL,
+};
+
+static struct usb_descriptor_header *hs_acc_descs[] = {
+	(struct usb_descriptor_header *) &acc_interface_desc,
+	(struct usb_descriptor_header *) &acc_highspeed_in_desc,
+	(struct usb_descriptor_header *) &acc_highspeed_out_desc,
+	NULL,
+};
+
+static struct usb_string acc_string_defs[] = {
+	[INTERFACE_STRING_INDEX].s	= "Android Accessory Interface",
+	{  },	/* end of list */
+};
+
+static struct usb_gadget_strings acc_string_table = {
+	.language		= 0x0409,	/* en-US */
+	.strings		= acc_string_defs,
+};
+
+static struct usb_gadget_strings *acc_strings[] = {
+	&acc_string_table,
+	NULL,
+};
+
+/* temporary variable used between acc_open() and acc_gadget_bind() */
+static struct acc_dev *_acc_dev;
+
+static inline struct acc_dev *func_to_dev(struct usb_function *f)
+{
+	return container_of(f, struct acc_dev, function);
+}
+
+static struct usb_request *acc_request_new(struct usb_ep *ep, int buffer_size)
+{
+	struct usb_request *req = usb_ep_alloc_request(ep, GFP_KERNEL);
+	if (!req)
+		return NULL;
+
+	/* now allocate buffers for the requests */
+	req->buf = kmalloc(buffer_size, GFP_KERNEL);
+	if (!req->buf) {
+		usb_ep_free_request(ep, req);
+		return NULL;
+	}
+
+	return req;
+}
+
+static void acc_request_free(struct usb_request *req, struct usb_ep *ep)
+{
+	if (req) {
+		kfree(req->buf);
+		usb_ep_free_request(ep, req);
+	}
+}
+
+/* add a request to the tail of a list */
+static void req_put(struct acc_dev *dev, struct list_head *head,
+		struct usb_request *req)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&dev->lock, flags);
+	list_add_tail(&req->list, head);
+	spin_unlock_irqrestore(&dev->lock, flags);
+}
+
+/* remove a request from the head of a list */
+static struct usb_request *req_get(struct acc_dev *dev, struct list_head *head)
+{
+	unsigned long flags;
+	struct usb_request *req;
+
+	spin_lock_irqsave(&dev->lock, flags);
+	if (list_empty(head)) {
+		req = 0;
+	} else {
+		req = list_first_entry(head, struct usb_request, list);
+		list_del(&req->list);
+	}
+	spin_unlock_irqrestore(&dev->lock, flags);
+	return req;
+}
+
+static void acc_set_disconnected(struct acc_dev *dev)
+{
+	dev->online = 0;
+	dev->disconnected = 1;
+}
+
+static void acc_complete_in(struct usb_ep *ep, struct usb_request *req)
+{
+	struct acc_dev *dev = _acc_dev;
+
+	if (req->status != 0)
+		acc_set_disconnected(dev);
+
+	req_put(dev, &dev->tx_idle, req);
+
+	wake_up(&dev->write_wq);
+}
+
+static void acc_complete_out(struct usb_ep *ep, struct usb_request *req)
+{
+	struct acc_dev *dev = _acc_dev;
+
+	dev->rx_done = 1;
+	if (req->status != 0)
+		acc_set_disconnected(dev);
+
+	wake_up(&dev->read_wq);
+}
+
+static void acc_complete_set_string(struct usb_ep *ep, struct usb_request *req)
+{
+	struct acc_dev	*dev = ep->driver_data;
+	char *string_dest = NULL;
+	int length = req->actual;
+
+	if (req->status != 0) {
+		pr_err("acc_complete_set_string, err %d\n", req->status);
+		return;
+	}
+
+	switch (dev->string_index) {
+	case ACCESSORY_STRING_MANUFACTURER:
+		string_dest = dev->manufacturer;
+		break;
+	case ACCESSORY_STRING_MODEL:
+		string_dest = dev->model;
+		break;
+	case ACCESSORY_STRING_DESCRIPTION:
+		string_dest = dev->description;
+		break;
+	case ACCESSORY_STRING_VERSION:
+		string_dest = dev->version;
+		break;
+	case ACCESSORY_STRING_URI:
+		string_dest = dev->uri;
+		break;
+	case ACCESSORY_STRING_SERIAL:
+		string_dest = dev->serial;
+		break;
+	}
+	if (string_dest) {
+		unsigned long flags;
+
+		if (length >= ACC_STRING_SIZE)
+			length = ACC_STRING_SIZE - 1;
+
+		spin_lock_irqsave(&dev->lock, flags);
+		memcpy(string_dest, req->buf, length);
+		/* ensure zero termination */
+		string_dest[length] = 0;
+		spin_unlock_irqrestore(&dev->lock, flags);
+	} else {
+		pr_err("unknown accessory string index %d\n",
+			dev->string_index);
+	}
+}
+
+static int __init create_bulk_endpoints(struct acc_dev *dev,
+				struct usb_endpoint_descriptor *in_desc,
+				struct usb_endpoint_descriptor *out_desc)
+{
+	struct usb_composite_dev *cdev = dev->cdev;
+	struct usb_request *req;
+	struct usb_ep *ep;
+	int i;
+
+	DBG(cdev, "create_bulk_endpoints dev: %p\n", dev);
+
+	ep = usb_ep_autoconfig(cdev->gadget, in_desc);
+	if (!ep) {
+		DBG(cdev, "usb_ep_autoconfig for ep_in failed\n");
+		return -ENODEV;
+	}
+	DBG(cdev, "usb_ep_autoconfig for ep_in got %s\n", ep->name);
+	ep->driver_data = dev;		/* claim the endpoint */
+	dev->ep_in = ep;
+
+	ep = usb_ep_autoconfig(cdev->gadget, out_desc);
+	if (!ep) {
+		DBG(cdev, "usb_ep_autoconfig for ep_out failed\n");
+		return -ENODEV;
+	}
+	DBG(cdev, "usb_ep_autoconfig for ep_out got %s\n", ep->name);
+	ep->driver_data = dev;		/* claim the endpoint */
+	dev->ep_out = ep;
+
+	ep = usb_ep_autoconfig(cdev->gadget, out_desc);
+	if (!ep) {
+		DBG(cdev, "usb_ep_autoconfig for ep_out failed\n");
+		return -ENODEV;
+	}
+	DBG(cdev, "usb_ep_autoconfig for ep_out got %s\n", ep->name);
+	ep->driver_data = dev;		/* claim the endpoint */
+	dev->ep_out = ep;
+
+	/* now allocate requests for our endpoints */
+	for (i = 0; i < TX_REQ_MAX; i++) {
+		req = acc_request_new(dev->ep_in, BULK_BUFFER_SIZE);
+		if (!req)
+			goto fail;
+		req->complete = acc_complete_in;
+		req_put(dev, &dev->tx_idle, req);
+	}
+	for (i = 0; i < RX_REQ_MAX; i++) {
+		req = acc_request_new(dev->ep_out, BULK_BUFFER_SIZE);
+		if (!req)
+			goto fail;
+		req->complete = acc_complete_out;
+		dev->rx_req[i] = req;
+	}
+
+	return 0;
+
+fail:
+	printk(KERN_ERR "acc_bind() could not allocate requests\n");
+	while ((req = req_get(dev, &dev->tx_idle)))
+		acc_request_free(req, dev->ep_in);
+	for (i = 0; i < RX_REQ_MAX; i++)
+		acc_request_free(dev->rx_req[i], dev->ep_out);
+	return -1;
+}
+
+static ssize_t acc_read(struct file *fp, char __user *buf,
+	size_t count, loff_t *pos)
+{
+	struct acc_dev *dev = fp->private_data;
+	struct usb_request *req;
+	int r = count, xfer;
+	int ret = 0;
+
+	pr_debug("acc_read(%d)\n", count);
+
+	if (dev->disconnected)
+		return -ENODEV;
+
+	if (count > BULK_BUFFER_SIZE)
+		count = BULK_BUFFER_SIZE;
+
+	/* we will block until we're online */
+	pr_debug("acc_read: waiting for online\n");
+	ret = wait_event_interruptible(dev->read_wq, dev->online);
+	if (ret < 0) {
+		r = ret;
+		goto done;
+	}
+
+requeue_req:
+	/* queue a request */
+	req = dev->rx_req[0];
+	req->length = count;
+	dev->rx_done = 0;
+	ret = usb_ep_queue(dev->ep_out, req, GFP_KERNEL);
+	if (ret < 0) {
+		r = -EIO;
+		goto done;
+	} else {
+		pr_debug("rx %p queue\n", req);
+	}
+
+	/* wait for a request to complete */
+	ret = wait_event_interruptible(dev->read_wq, dev->rx_done);
+	if (ret < 0) {
+		r = ret;
+		usb_ep_dequeue(dev->ep_out, req);
+		goto done;
+	}
+	if (dev->online) {
+		/* If we got a 0-len packet, throw it back and try again. */
+		if (req->actual == 0)
+			goto requeue_req;
+
+		pr_debug("rx %p %d\n", req, req->actual);
+		xfer = (req->actual < count) ? req->actual : count;
+		r = xfer;
+		if (copy_to_user(buf, req->buf, xfer))
+			r = -EFAULT;
+	} else
+		r = -EIO;
+
+done:
+	pr_debug("acc_read returning %d\n", r);
+	return r;
+}
+
+static ssize_t acc_write(struct file *fp, const char __user *buf,
+	size_t count, loff_t *pos)
+{
+	struct acc_dev *dev = fp->private_data;
+	struct usb_request *req = 0;
+	int r = count, xfer;
+	int ret;
+
+	pr_debug("acc_write(%d)\n", count);
+
+	if (!dev->online || dev->disconnected)
+		return -ENODEV;
+
+	while (count > 0) {
+		if (!dev->online) {
+			pr_debug("acc_write dev->error\n");
+			r = -EIO;
+			break;
+		}
+
+		/* get an idle tx request to use */
+		req = 0;
+		ret = wait_event_interruptible(dev->write_wq,
+			((req = req_get(dev, &dev->tx_idle)) || !dev->online));
+		if (!req) {
+			r = ret;
+			break;
+		}
+
+		if (count > BULK_BUFFER_SIZE)
+			xfer = BULK_BUFFER_SIZE;
+		else
+			xfer = count;
+		if (copy_from_user(req->buf, buf, xfer)) {
+			r = -EFAULT;
+			break;
+		}
+
+		req->length = xfer;
+		ret = usb_ep_queue(dev->ep_in, req, GFP_KERNEL);
+		if (ret < 0) {
+			pr_debug("acc_write: xfer error %d\n", ret);
+			r = -EIO;
+			break;
+		}
+
+		buf += xfer;
+		count -= xfer;
+
+		/* zero this so we don't try to free it on error exit */
+		req = 0;
+	}
+
+	if (req)
+		req_put(dev, &dev->tx_idle, req);
+
+	pr_debug("acc_write returning %d\n", r);
+	return r;
+}
+
+static long acc_ioctl(struct file *fp, unsigned code, unsigned long value)
+{
+	struct acc_dev *dev = fp->private_data;
+	char *src = NULL;
+	int ret;
+
+	switch (code) {
+	case ACCESSORY_GET_STRING_MANUFACTURER:
+		src = dev->manufacturer;
+		break;
+	case ACCESSORY_GET_STRING_MODEL:
+		src = dev->model;
+		break;
+	case ACCESSORY_GET_STRING_DESCRIPTION:
+		src = dev->description;
+		break;
+	case ACCESSORY_GET_STRING_VERSION:
+		src = dev->version;
+		break;
+	case ACCESSORY_GET_STRING_URI:
+		src = dev->uri;
+		break;
+	case ACCESSORY_GET_STRING_SERIAL:
+		src = dev->serial;
+		break;
+	case ACCESSORY_IS_START_REQUESTED:
+		return dev->start_requested;
+	}
+	if (!src)
+		return -EINVAL;
+
+	ret = strlen(src) + 1;
+	if (copy_to_user((void __user *)value, src, ret))
+		ret = -EFAULT;
+	return ret;
+}
+
+static int acc_open(struct inode *ip, struct file *fp)
+{
+	printk(KERN_INFO "acc_open\n");
+	if (atomic_xchg(&_acc_dev->open_excl, 1))
+		return -EBUSY;
+
+	_acc_dev->disconnected = 0;
+	fp->private_data = _acc_dev;
+	return 0;
+}
+
+static int acc_release(struct inode *ip, struct file *fp)
+{
+	printk(KERN_INFO "acc_release\n");
+
+	WARN_ON(!atomic_xchg(&_acc_dev->open_excl, 0));
+	_acc_dev->disconnected = 0;
+	return 0;
+}
+
+/* file operations for /dev/acc_usb */
+static const struct file_operations acc_fops = {
+	.owner = THIS_MODULE,
+	.read = acc_read,
+	.write = acc_write,
+	.unlocked_ioctl = acc_ioctl,
+	.open = acc_open,
+	.release = acc_release,
+};
+
+static struct miscdevice acc_device = {
+	.minor = MISC_DYNAMIC_MINOR,
+	.name = "usb_accessory",
+	.fops = &acc_fops,
+};
+
+
+static int acc_ctrlrequest(struct usb_composite_dev *cdev,
+				const struct usb_ctrlrequest *ctrl)
+{
+	struct acc_dev	*dev = _acc_dev;
+	int	value = -EOPNOTSUPP;
+	u8 b_requestType = ctrl->bRequestType;
+	u8 b_request = ctrl->bRequest;
+	u16	w_index = le16_to_cpu(ctrl->wIndex);
+	u16	w_value = le16_to_cpu(ctrl->wValue);
+	u16	w_length = le16_to_cpu(ctrl->wLength);
+
+/*
+	printk(KERN_INFO "acc_ctrlrequest "
+			"%02x.%02x v%04x i%04x l%u\n",
+			b_requestType, b_request,
+			w_value, w_index, w_length);
+*/
+
+	if (b_requestType == (USB_DIR_OUT | USB_TYPE_VENDOR)) {
+		if (b_request == ACCESSORY_START) {
+			dev->start_requested = 1;
+			schedule_delayed_work(
+				&dev->work, msecs_to_jiffies(10));
+			value = 0;
+		} else if (b_request == ACCESSORY_SEND_STRING) {
+			dev->string_index = w_index;
+			cdev->gadget->ep0->driver_data = dev;
+			cdev->req->complete = acc_complete_set_string;
+			value = w_length;
+		}
+	} else if (b_requestType == (USB_DIR_IN | USB_TYPE_VENDOR)) {
+		if (b_request == ACCESSORY_GET_PROTOCOL) {
+			*((u16 *)cdev->req->buf) = PROTOCOL_VERSION;
+			value = sizeof(u16);
+
+			/* clear any string left over from a previous session */
+			memset(dev->manufacturer, 0, sizeof(dev->manufacturer));
+			memset(dev->model, 0, sizeof(dev->model));
+			memset(dev->description, 0, sizeof(dev->description));
+			memset(dev->version, 0, sizeof(dev->version));
+			memset(dev->uri, 0, sizeof(dev->uri));
+			memset(dev->serial, 0, sizeof(dev->serial));
+			dev->start_requested = 0;
+		}
+	}
+
+	if (value >= 0) {
+		cdev->req->zero = 0;
+		cdev->req->length = value;
+		value = usb_ep_queue(cdev->gadget->ep0, cdev->req, GFP_ATOMIC);
+		if (value < 0)
+			ERROR(cdev, "%s setup response queue error\n",
+				__func__);
+	}
+
+	if (value == -EOPNOTSUPP)
+		VDBG(cdev,
+			"unknown class-specific control req "
+			"%02x.%02x v%04x i%04x l%u\n",
+			ctrl->bRequestType, ctrl->bRequest,
+			w_value, w_index, w_length);
+	return value;
+}
+
+static int
+acc_function_bind(struct usb_configuration *c, struct usb_function *f)
+{
+	struct usb_composite_dev *cdev = c->cdev;
+	struct acc_dev	*dev = func_to_dev(f);
+	int			id;
+	int			ret;
+
+	DBG(cdev, "acc_function_bind dev: %p\n", dev);
+
+	dev->start_requested = 0;
+
+	/* allocate interface ID(s) */
+	id = usb_interface_id(c, f);
+	if (id < 0)
+		return id;
+	acc_interface_desc.bInterfaceNumber = id;
+
+	/* allocate endpoints */
+	ret = create_bulk_endpoints(dev, &acc_fullspeed_in_desc,
+			&acc_fullspeed_out_desc);
+	if (ret)
+		return ret;
+
+	/* support high speed hardware */
+	if (gadget_is_dualspeed(c->cdev->gadget)) {
+		acc_highspeed_in_desc.bEndpointAddress =
+			acc_fullspeed_in_desc.bEndpointAddress;
+		acc_highspeed_out_desc.bEndpointAddress =
+			acc_fullspeed_out_desc.bEndpointAddress;
+	}
+
+	DBG(cdev, "%s speed %s: IN/%s, OUT/%s\n",
+			gadget_is_dualspeed(c->cdev->gadget) ? "dual" : "full",
+			f->name, dev->ep_in->name, dev->ep_out->name);
+	return 0;
+}
+
+static void
+acc_function_unbind(struct usb_configuration *c, struct usb_function *f)
+{
+	struct acc_dev	*dev = func_to_dev(f);
+	struct usb_request *req;
+	int i;
+
+	while ((req = req_get(dev, &dev->tx_idle)))
+		acc_request_free(req, dev->ep_in);
+	for (i = 0; i < RX_REQ_MAX; i++)
+		acc_request_free(dev->rx_req[i], dev->ep_out);
+}
+
+static void acc_work(struct work_struct *data)
+{
+	char *envp[2] = { "ACCESSORY=START", NULL };
+	kobject_uevent_env(&acc_device.this_device->kobj, KOBJ_CHANGE, envp);
+}
+
+static int acc_function_set_alt(struct usb_function *f,
+		unsigned intf, unsigned alt)
+{
+	struct acc_dev	*dev = func_to_dev(f);
+	struct usb_composite_dev *cdev = f->config->cdev;
+	int ret;
+
+	DBG(cdev, "acc_function_set_alt intf: %d alt: %d\n", intf, alt);
+
+	ret = config_ep_by_speed(cdev->gadget, f, dev->ep_in);
+	if (ret)
+		return ret;
+
+	ret = usb_ep_enable(dev->ep_in);
+	if (ret)
+		return ret;
+
+	ret = config_ep_by_speed(cdev->gadget, f, dev->ep_out);
+	if (ret)
+		return ret;
+
+	ret = usb_ep_enable(dev->ep_out);
+	if (ret) {
+		usb_ep_disable(dev->ep_in);
+		return ret;
+	}
+
+	dev->online = 1;
+
+	/* readers may be blocked waiting for us to go online */
+	wake_up(&dev->read_wq);
+	return 0;
+}
+
+static void acc_function_disable(struct usb_function *f)
+{
+	struct acc_dev	*dev = func_to_dev(f);
+	struct usb_composite_dev	*cdev = dev->cdev;
+
+	DBG(cdev, "acc_function_disable\n");
+	acc_set_disconnected(dev);
+	usb_ep_disable(dev->ep_in);
+	usb_ep_disable(dev->ep_out);
+
+	/* readers may be blocked waiting for us to go online */
+	wake_up(&dev->read_wq);
+
+	VDBG(cdev, "%s disabled\n", dev->function.name);
+}
+
+static int acc_bind_config(struct usb_configuration *c)
+{
+	struct acc_dev *dev = _acc_dev;
+	int ret;
+
+	printk(KERN_INFO "acc_bind_config\n");
+
+	/* allocate a string ID for our interface */
+	if (acc_string_defs[INTERFACE_STRING_INDEX].id == 0) {
+		ret = usb_string_id(c->cdev);
+		if (ret < 0)
+			return ret;
+		acc_string_defs[INTERFACE_STRING_INDEX].id = ret;
+		acc_interface_desc.iInterface = ret;
+	}
+
+	dev->cdev = c->cdev;
+	dev->function.name = "accessory";
+	dev->function.strings = acc_strings,
+	dev->function.descriptors = fs_acc_descs;
+	dev->function.hs_descriptors = hs_acc_descs;
+	dev->function.bind = acc_function_bind;
+	dev->function.unbind = acc_function_unbind;
+	dev->function.set_alt = acc_function_set_alt;
+	dev->function.disable = acc_function_disable;
+
+	return usb_add_function(c, &dev->function);
+}
+
+static int acc_setup(void)
+{
+	struct acc_dev *dev;
+	int ret;
+
+	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
+	if (!dev)
+		return -ENOMEM;
+
+	spin_lock_init(&dev->lock);
+	init_waitqueue_head(&dev->read_wq);
+	init_waitqueue_head(&dev->write_wq);
+	atomic_set(&dev->open_excl, 0);
+	INIT_LIST_HEAD(&dev->tx_idle);
+	INIT_DELAYED_WORK(&dev->work, acc_work);
+
+	/* _acc_dev must be set before calling usb_gadget_register_driver */
+	_acc_dev = dev;
+
+	ret = misc_register(&acc_device);
+	if (ret)
+		goto err;
+
+	return 0;
+
+err:
+	kfree(dev);
+	printk(KERN_ERR "USB accessory gadget driver failed to initialize\n");
+	return ret;
+}
+
+static void acc_cleanup(void)
+{
+	misc_deregister(&acc_device);
+	kfree(_acc_dev);
+	_acc_dev = NULL;
+}
diff --git a/include/linux/usb/f_accessory.h b/include/linux/usb/f_accessory.h
new file mode 100644
index 0000000..5b2dcf9
--- /dev/null
+++ b/include/linux/usb/f_accessory.h
@@ -0,0 +1,83 @@
+/*
+ * Gadget Function Driver for Android USB accessories
+ *
+ * Copyright (C) 2011 Google, Inc.
+ * Author: Mike Lockwood <lockwood@android.com>
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#ifndef __LINUX_USB_F_ACCESSORY_H
+#define __LINUX_USB_F_ACCESSORY_H
+
+/* Use Google Vendor ID when in accessory mode */
+#define USB_ACCESSORY_VENDOR_ID 0x18D1
+
+
+/* Product ID to use when in accessory mode */
+#define USB_ACCESSORY_PRODUCT_ID 0x2D00
+
+/* Product ID to use when in accessory mode and adb is enabled */
+#define USB_ACCESSORY_ADB_PRODUCT_ID 0x2D01
+
+/* Indexes for strings sent by the host via ACCESSORY_SEND_STRING */
+#define ACCESSORY_STRING_MANUFACTURER   0
+#define ACCESSORY_STRING_MODEL          1
+#define ACCESSORY_STRING_DESCRIPTION    2
+#define ACCESSORY_STRING_VERSION        3
+#define ACCESSORY_STRING_URI            4
+#define ACCESSORY_STRING_SERIAL         5
+
+/* Control request for retrieving device's protocol version (currently 1)
+ *
+ *	requestType:    USB_DIR_IN | USB_TYPE_VENDOR
+ *	request:        ACCESSORY_GET_PROTOCOL
+ *	value:          0
+ *	index:          0
+ *	data            version number (16 bits little endian)
+ */
+#define ACCESSORY_GET_PROTOCOL  51
+
+/* Control request for host to send a string to the device
+ *
+ *	requestType:    USB_DIR_OUT | USB_TYPE_VENDOR
+ *	request:        ACCESSORY_SEND_STRING
+ *	value:          0
+ *	index:          string ID
+ *	data            zero terminated UTF8 string
+ *
+ *  The device can later retrieve these strings via the
+ *  ACCESSORY_GET_STRING_* ioctls
+ */
+#define ACCESSORY_SEND_STRING   52
+
+/* Control request for starting device in accessory mode.
+ * The host sends this after setting all its strings to the device.
+ *
+ *	requestType:    USB_DIR_OUT | USB_TYPE_VENDOR
+ *	request:        ACCESSORY_START
+ *	value:          0
+ *	index:          0
+ *	data            none
+ */
+#define ACCESSORY_START         53
+
+/* ioctls for retrieving strings set by the host */
+#define ACCESSORY_GET_STRING_MANUFACTURER   _IOW('M', 1, char[256])
+#define ACCESSORY_GET_STRING_MODEL          _IOW('M', 2, char[256])
+#define ACCESSORY_GET_STRING_DESCRIPTION    _IOW('M', 3, char[256])
+#define ACCESSORY_GET_STRING_VERSION        _IOW('M', 4, char[256])
+#define ACCESSORY_GET_STRING_URI            _IOW('M', 5, char[256])
+#define ACCESSORY_GET_STRING_SERIAL         _IOW('M', 6, char[256])
+/* returns 1 if there is a start request pending */
+#define ACCESSORY_IS_START_REQUESTED        _IO('M', 7)
+
+#endif /* __LINUX_USB_F_ACCESSORY_H */