usb: gadget: Add Android Composite Gadget driver

The Android Gadget driver is a composite driver that allows
userspace to change at runtime the list of functions enabled in
its configuration and to configure these functions. It supports
multiple functions: acm, adb, rndis, mtp/ptp, mass storage and
accessory.

It is usually controlled by a daemon that changes the configuration
based on user settings. For example, rndis is enabled when the user
enables sharing the phone data connection and adb (Android Debug
Bridge) is only enabled when the user wants to debug applications
for security reasons.

As an example on how to use it, the following shell commands will
make the gadget disconnect from the host and make it be re-enumerated
as a composite with 1 rndis and 2 acm interfaces, and a different
product id:

echo 0       > /sys/class/android_usb/android0/enable
echo rndis,acm > /sys/class/android_usb/android0/functions
echo 2       > /sys/class/android_usb/android0/f_acm/instances
echo 2d01    > /sys/class/android_usb/android0/idProduct
echo 1       > /sys/class/android_usb/android0/enable

The driver requires a gadget controller that supports software
control of the D+ pullup and the controller driver must support
disabling the pullup during composite_bind.

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

3 files changed, 1087 insertions, 0 deletions

diff --git a/drivers/usb/gadget/Kconfig b/drivers/usb/gadget/Kconfig
index 2633f759511..a04b3f57814 100644
--- a/drivers/usb/gadget/Kconfig
+++ b/drivers/usb/gadget/Kconfig
@@ -846,6 +846,15 @@ config USB_G_PRINTER
 	  For more information, see Documentation/usb/gadget_printer.txt
 	  which includes sample code for accessing the device file.
 
+config USB_G_ANDROID
+	boolean "Android Composite Gadget"
+	help
+	  The Android Composite Gadget supports multiple USB
+	  functions: adb, acm, mass storage, mtp, accessory
+	  and rndis.
+	  Each function can be configured and enabled/disabled
+	  dynamically from userspace through a sysfs interface.
+
 config USB_CDC_COMPOSITE
 	tristate "CDC Composite Device (Ethernet and ACM)"
 	depends on NET
diff --git a/drivers/usb/gadget/Makefile b/drivers/usb/gadget/Makefile
index b7f6eefc392..b91866a6532 100644
--- a/drivers/usb/gadget/Makefile
+++ b/drivers/usb/gadget/Makefile
@@ -52,6 +52,7 @@ g_nokia-y			:= nokia.o
 g_webcam-y			:= webcam.o
 g_ncm-y				:= ncm.o
 g_acm_ms-y			:= acm_ms.o
+g_android-y			:= android.o
 
 obj-$(CONFIG_USB_ZERO)		+= g_zero.o
 obj-$(CONFIG_USB_AUDIO)		+= g_audio.o
@@ -71,3 +72,4 @@ obj-$(CONFIG_USB_G_NOKIA)	+= g_nokia.o
 obj-$(CONFIG_USB_G_WEBCAM)	+= g_webcam.o
 obj-$(CONFIG_USB_G_NCM)		+= g_ncm.o
 obj-$(CONFIG_USB_G_ACM_MS)	+= g_acm_ms.o
+obj-$(CONFIG_USB_G_ANDROID)	+= g_android.o
diff --git a/drivers/usb/gadget/android.c b/drivers/usb/gadget/android.c
new file mode 100644
index 00000000000..6d67d6d8057
--- /dev/null
+++ b/drivers/usb/gadget/android.c
@@ -0,0 +1,1076 @@
+/*
+ * Gadget Driver for Android
+ *
+ * Copyright (C) 2008 Google, Inc.
+ * Author: Mike Lockwood <lockwood@android.com>
+ *         Benoit Goby <benoit@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.
+ *
+ */
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <linux/delay.h>
+#include <linux/kernel.h>
+#include <linux/utsname.h>
+#include <linux/platform_device.h>
+
+#include <linux/usb/ch9.h>
+#include <linux/usb/composite.h>
+#include <linux/usb/gadget.h>
+
+#include "gadget_chips.h"
+
+/*
+ * 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 "usbstring.c"
+#include "config.c"
+#include "epautoconf.c"
+#include "composite.c"
+
+#include "f_mass_storage.c"
+#include "u_serial.c"
+#include "f_acm.c"
+#define USB_ETH_RNDIS y
+#include "f_rndis.c"
+#include "rndis.c"
+#include "u_ether.c"
+
+MODULE_AUTHOR("Mike Lockwood");
+MODULE_DESCRIPTION("Android Composite USB Driver");
+MODULE_LICENSE("GPL");
+MODULE_VERSION("1.0");
+
+static const char longname[] = "Gadget Android";
+
+/* Default vendor and product IDs, overridden by userspace */
+#define VENDOR_ID		0x18D1
+#define PRODUCT_ID		0x0001
+
+struct android_usb_function {
+	char *name;
+	void *config;
+
+	struct device *dev;
+	char *dev_name;
+	struct device_attribute **attributes;
+
+	/* for android_dev.enabled_functions */
+	struct list_head enabled_list;
+
+	/* Optional: initialization during gadget bind */
+	int (*init)(struct android_usb_function *, struct usb_composite_dev *);
+	/* Optional: cleanup during gadget unbind */
+	void (*cleanup)(struct android_usb_function *);
+
+	int (*bind_config)(struct android_usb_function *,
+			   struct usb_configuration *);
+
+	/* Optional: called when the configuration is removed */
+	void (*unbind_config)(struct android_usb_function *,
+			      struct usb_configuration *);
+	/* Optional: handle ctrl requests before the device is configured */
+	int (*ctrlrequest)(struct android_usb_function *,
+					struct usb_composite_dev *,
+					const struct usb_ctrlrequest *);
+};
+
+struct android_dev {
+	struct android_usb_function **functions;
+	struct list_head enabled_functions;
+	struct usb_composite_dev *cdev;
+	struct device *dev;
+
+	bool enabled;
+	struct mutex mutex;
+	bool connected;
+	bool sw_connected;
+	struct work_struct work;
+};
+
+static struct class *android_class;
+static struct android_dev *_android_dev;
+static int android_bind_config(struct usb_configuration *c);
+static void android_unbind_config(struct usb_configuration *c);
+
+/* string IDs are assigned dynamically */
+#define STRING_MANUFACTURER_IDX		0
+#define STRING_PRODUCT_IDX		1
+#define STRING_SERIAL_IDX		2
+
+static char manufacturer_string[256];
+static char product_string[256];
+static char serial_string[256];
+
+/* String Table */
+static struct usb_string strings_dev[] = {
+	[STRING_MANUFACTURER_IDX].s = manufacturer_string,
+	[STRING_PRODUCT_IDX].s = product_string,
+	[STRING_SERIAL_IDX].s = serial_string,
+	{  }			/* end of list */
+};
+
+static struct usb_gadget_strings stringtab_dev = {
+	.language	= 0x0409,	/* en-us */
+	.strings	= strings_dev,
+};
+
+static struct usb_gadget_strings *dev_strings[] = {
+	&stringtab_dev,
+	NULL,
+};
+
+static struct usb_device_descriptor device_desc = {
+	.bLength              = sizeof(device_desc),
+	.bDescriptorType      = USB_DT_DEVICE,
+	.bcdUSB               = __constant_cpu_to_le16(0x0200),
+	.bDeviceClass         = USB_CLASS_PER_INTERFACE,
+	.idVendor             = __constant_cpu_to_le16(VENDOR_ID),
+	.idProduct            = __constant_cpu_to_le16(PRODUCT_ID),
+	.bcdDevice            = __constant_cpu_to_le16(0xffff),
+	.bNumConfigurations   = 1,
+};
+
+static struct usb_configuration android_config_driver = {
+	.label		= "android",
+	.unbind		= android_unbind_config,
+	.bConfigurationValue = 1,
+	.bmAttributes	= USB_CONFIG_ATT_ONE | USB_CONFIG_ATT_SELFPOWER,
+	.bMaxPower	= 0xFA, /* 500ma */
+};
+
+static void android_work(struct work_struct *data)
+{
+	struct android_dev *dev = container_of(data, struct android_dev, work);
+	struct usb_composite_dev *cdev = dev->cdev;
+	char *disconnected[2] = { "USB_STATE=DISCONNECTED", NULL };
+	char *connected[2]    = { "USB_STATE=CONNECTED", NULL };
+	char *configured[2]   = { "USB_STATE=CONFIGURED", NULL };
+	char **uevent_envp = NULL;
+	unsigned long flags;
+
+	spin_lock_irqsave(&cdev->lock, flags);
+	if (cdev->config)
+		uevent_envp = configured;
+	else if (dev->connected != dev->sw_connected)
+		uevent_envp = dev->connected ? connected : disconnected;
+	dev->sw_connected = dev->connected;
+	spin_unlock_irqrestore(&cdev->lock, flags);
+
+	if (uevent_envp) {
+		kobject_uevent_env(&dev->dev->kobj, KOBJ_CHANGE, uevent_envp);
+		pr_info("%s: sent uevent %s\n", __func__, uevent_envp[0]);
+	} else {
+		pr_info("%s: did not send uevent (%d %d %p)\n", __func__,
+			 dev->connected, dev->sw_connected, cdev->config);
+	}
+}
+
+
+/*-------------------------------------------------------------------------*/
+/* Supported functions initialization */
+
+#define MAX_ACM_INSTANCES 4
+struct acm_function_config {
+	int instances;
+};
+
+static int
+acm_function_init(struct android_usb_function *f,
+		struct usb_composite_dev *cdev)
+{
+	f->config = kzalloc(sizeof(struct acm_function_config), GFP_KERNEL);
+	if (!f->config)
+		return -ENOMEM;
+
+	return gserial_setup(cdev->gadget, MAX_ACM_INSTANCES);
+}
+
+static void acm_function_cleanup(struct android_usb_function *f)
+{
+	gserial_cleanup();
+	kfree(f->config);
+	f->config = NULL;
+}
+
+static int
+acm_function_bind_config(struct android_usb_function *f,
+		struct usb_configuration *c)
+{
+	int i;
+	int ret = 0;
+	struct acm_function_config *config = f->config;
+
+	for (i = 0; i < config->instances; i++) {
+		ret = acm_bind_config(c, i);
+		if (ret) {
+			pr_err("Could not bind acm%u config\n", i);
+			break;
+		}
+	}
+
+	return ret;
+}
+
+static ssize_t acm_instances_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct android_usb_function *f = dev_get_drvdata(dev);
+	struct acm_function_config *config = f->config;
+	return sprintf(buf, "%d\n", config->instances);
+}
+
+static ssize_t acm_instances_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t size)
+{
+	struct android_usb_function *f = dev_get_drvdata(dev);
+	struct acm_function_config *config = f->config;
+	int value;
+
+	sscanf(buf, "%d", &value);
+	if (value > MAX_ACM_INSTANCES)
+		value = MAX_ACM_INSTANCES;
+	config->instances = value;
+	return size;
+}
+
+static DEVICE_ATTR(instances, S_IRUGO | S_IWUSR, acm_instances_show,
+						 acm_instances_store);
+static struct device_attribute *acm_function_attributes[] = {
+	&dev_attr_instances,
+	NULL
+};
+
+static struct android_usb_function acm_function = {
+	.name		= "acm",
+	.init		= acm_function_init,
+	.cleanup	= acm_function_cleanup,
+	.bind_config	= acm_function_bind_config,
+	.attributes	= acm_function_attributes,
+};
+
+
+struct rndis_function_config {
+	u8      ethaddr[ETH_ALEN];
+	u32     vendorID;
+	char	manufacturer[256];
+	/* "Wireless" RNDIS; auto-detected by Windows */
+	bool	wceis;
+};
+
+static int
+rndis_function_init(struct android_usb_function *f,
+		struct usb_composite_dev *cdev)
+{
+	f->config = kzalloc(sizeof(struct rndis_function_config), GFP_KERNEL);
+	if (!f->config)
+		return -ENOMEM;
+	return 0;
+}
+
+static void rndis_function_cleanup(struct android_usb_function *f)
+{
+	kfree(f->config);
+	f->config = NULL;
+}
+
+static int
+rndis_function_bind_config(struct android_usb_function *f,
+		struct usb_configuration *c)
+{
+	int ret;
+	struct rndis_function_config *rndis = f->config;
+
+	if (!rndis) {
+		pr_err("%s: rndis_pdata\n", __func__);
+		return -1;
+	}
+
+	pr_info("%s MAC: %02X:%02X:%02X:%02X:%02X:%02X\n", __func__,
+		rndis->ethaddr[0], rndis->ethaddr[1], rndis->ethaddr[2],
+		rndis->ethaddr[3], rndis->ethaddr[4], rndis->ethaddr[5]);
+
+	ret = gether_setup_name(c->cdev->gadget, rndis->ethaddr, "rndis");
+	if (ret) {
+		pr_err("%s: gether_setup failed\n", __func__);
+		return ret;
+	}
+
+	if (rndis->wceis) {
+		/* "Wireless" RNDIS; auto-detected by Windows */
+		rndis_iad_descriptor.bFunctionClass =
+						USB_CLASS_WIRELESS_CONTROLLER;
+		rndis_iad_descriptor.bFunctionSubClass = 0x01;
+		rndis_iad_descriptor.bFunctionProtocol = 0x03;
+		rndis_control_intf.bInterfaceClass =
+						USB_CLASS_WIRELESS_CONTROLLER;
+		rndis_control_intf.bInterfaceSubClass =	 0x01;
+		rndis_control_intf.bInterfaceProtocol =	 0x03;
+	}
+
+	return rndis_bind_config_vendor(c, rndis->ethaddr, rndis->vendorID,
+					   rndis->manufacturer);
+}
+
+static void rndis_function_unbind_config(struct android_usb_function *f,
+						struct usb_configuration *c)
+{
+	gether_cleanup();
+}
+
+static ssize_t rndis_manufacturer_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct android_usb_function *f = dev_get_drvdata(dev);
+	struct rndis_function_config *config = f->config;
+	return sprintf(buf, "%s\n", config->manufacturer);
+}
+
+static ssize_t rndis_manufacturer_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t size)
+{
+	struct android_usb_function *f = dev_get_drvdata(dev);
+	struct rndis_function_config *config = f->config;
+
+	if (size >= sizeof(config->manufacturer))
+		return -EINVAL;
+	if (sscanf(buf, "%s", config->manufacturer) == 1)
+		return size;
+	return -1;
+}
+
+static DEVICE_ATTR(manufacturer, S_IRUGO | S_IWUSR, rndis_manufacturer_show,
+						    rndis_manufacturer_store);
+
+static ssize_t rndis_wceis_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct android_usb_function *f = dev_get_drvdata(dev);
+	struct rndis_function_config *config = f->config;
+	return sprintf(buf, "%d\n", config->wceis);
+}
+
+static ssize_t rndis_wceis_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t size)
+{
+	struct android_usb_function *f = dev_get_drvdata(dev);
+	struct rndis_function_config *config = f->config;
+	int value;
+
+	if (sscanf(buf, "%d", &value) == 1) {
+		config->wceis = value;
+		return size;
+	}
+	return -EINVAL;
+}
+
+static DEVICE_ATTR(wceis, S_IRUGO | S_IWUSR, rndis_wceis_show,
+					     rndis_wceis_store);
+
+static ssize_t rndis_ethaddr_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct android_usb_function *f = dev_get_drvdata(dev);
+	struct rndis_function_config *rndis = f->config;
+	return sprintf(buf, "%02x:%02x:%02x:%02x:%02x:%02x\n",
+		rndis->ethaddr[0], rndis->ethaddr[1], rndis->ethaddr[2],
+		rndis->ethaddr[3], rndis->ethaddr[4], rndis->ethaddr[5]);
+}
+
+static ssize_t rndis_ethaddr_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t size)
+{
+	struct android_usb_function *f = dev_get_drvdata(dev);
+	struct rndis_function_config *rndis = f->config;
+
+	if (sscanf(buf, "%02x:%02x:%02x:%02x:%02x:%02x\n",
+		    (int *)&rndis->ethaddr[0], (int *)&rndis->ethaddr[1],
+		    (int *)&rndis->ethaddr[2], (int *)&rndis->ethaddr[3],
+		    (int *)&rndis->ethaddr[4], (int *)&rndis->ethaddr[5]) == 6)
+		return size;
+	return -EINVAL;
+}
+
+static DEVICE_ATTR(ethaddr, S_IRUGO | S_IWUSR, rndis_ethaddr_show,
+					       rndis_ethaddr_store);
+
+static ssize_t rndis_vendorID_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct android_usb_function *f = dev_get_drvdata(dev);
+	struct rndis_function_config *config = f->config;
+	return sprintf(buf, "%04x\n", config->vendorID);
+}
+
+static ssize_t rndis_vendorID_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t size)
+{
+	struct android_usb_function *f = dev_get_drvdata(dev);
+	struct rndis_function_config *config = f->config;
+	int value;
+
+	if (sscanf(buf, "%04x", &value) == 1) {
+		config->vendorID = value;
+		return size;
+	}
+	return -EINVAL;
+}
+
+static DEVICE_ATTR(vendorID, S_IRUGO | S_IWUSR, rndis_vendorID_show,
+						rndis_vendorID_store);
+
+static struct device_attribute *rndis_function_attributes[] = {
+	&dev_attr_manufacturer,
+	&dev_attr_wceis,
+	&dev_attr_ethaddr,
+	&dev_attr_vendorID,
+	NULL
+};
+
+static struct android_usb_function rndis_function = {
+	.name		= "rndis",
+	.init		= rndis_function_init,
+	.cleanup	= rndis_function_cleanup,
+	.bind_config	= rndis_function_bind_config,
+	.unbind_config	= rndis_function_unbind_config,
+	.attributes	= rndis_function_attributes,
+};
+
+
+struct mass_storage_function_config {
+	struct fsg_config fsg;
+	struct fsg_common *common;
+};
+
+static int mass_storage_function_init(struct android_usb_function *f,
+					struct usb_composite_dev *cdev)
+{
+	struct mass_storage_function_config *config;
+	struct fsg_common *common;
+	int err;
+
+	config = kzalloc(sizeof(struct mass_storage_function_config),
+								GFP_KERNEL);
+	if (!config)
+		return -ENOMEM;
+
+	config->fsg.nluns = 1;
+	config->fsg.luns[0].removable = 1;
+
+	common = fsg_common_init(NULL, cdev, &config->fsg);
+	if (IS_ERR(common)) {
+		kfree(config);
+		return PTR_ERR(common);
+	}
+
+	err = sysfs_create_link(&f->dev->kobj,
+				&common->luns[0].dev.kobj,
+				"lun");
+	if (err) {
+		kfree(config);
+		return err;
+	}
+
+	config->common = common;
+	f->config = config;
+	return 0;
+}
+
+static void mass_storage_function_cleanup(struct android_usb_function *f)
+{
+	kfree(f->config);
+	f->config = NULL;
+}
+
+static int mass_storage_function_bind_config(struct android_usb_function *f,
+						struct usb_configuration *c)
+{
+	struct mass_storage_function_config *config = f->config;
+	return fsg_bind_config(c->cdev, c, config->common);
+}
+
+static ssize_t mass_storage_inquiry_show(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	struct android_usb_function *f = dev_get_drvdata(dev);
+	struct mass_storage_function_config *config = f->config;
+	return sprintf(buf, "%s\n", config->common->inquiry_string);
+}
+
+static ssize_t mass_storage_inquiry_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t size)
+{
+	struct android_usb_function *f = dev_get_drvdata(dev);
+	struct mass_storage_function_config *config = f->config;
+	if (size >= sizeof(config->common->inquiry_string))
+		return -EINVAL;
+	if (sscanf(buf, "%s", config->common->inquiry_string) != 1)
+		return -EINVAL;
+	return size;
+}
+
+static DEVICE_ATTR(inquiry_string, S_IRUGO | S_IWUSR,
+					mass_storage_inquiry_show,
+					mass_storage_inquiry_store);
+
+static struct device_attribute *mass_storage_function_attributes[] = {
+	&dev_attr_inquiry_string,
+	NULL
+};
+
+static struct android_usb_function mass_storage_function = {
+	.name		= "mass_storage",
+	.init		= mass_storage_function_init,
+	.cleanup	= mass_storage_function_cleanup,
+	.bind_config	= mass_storage_function_bind_config,
+	.attributes	= mass_storage_function_attributes,
+};
+
+
+static struct android_usb_function *supported_functions[] = {
+	&acm_function,
+	&rndis_function,
+	&mass_storage_function,
+	NULL
+};
+
+
+static int android_init_functions(struct android_usb_function **functions,
+				  struct usb_composite_dev *cdev)
+{
+	struct android_dev *dev = _android_dev;
+	struct android_usb_function *f;
+	struct device_attribute **attrs;
+	struct device_attribute *attr;
+	int err;
+	int index = 0;
+
+	for (; (f = *functions++); index++) {
+		f->dev_name = kasprintf(GFP_KERNEL, "f_%s", f->name);
+		f->dev = device_create(android_class, dev->dev,
+				MKDEV(0, index), f, f->dev_name);
+		if (IS_ERR(f->dev)) {
+			pr_err("%s: Failed to create dev %s", __func__,
+							f->dev_name);
+			err = PTR_ERR(f->dev);
+			goto err_create;
+		}
+
+		if (f->init) {
+			err = f->init(f, cdev);
+			if (err) {
+				pr_err("%s: Failed to init %s", __func__,
+								f->name);
+				goto err_out;
+			}
+		}
+
+		attrs = f->attributes;
+		if (attrs) {
+			while ((attr = *attrs++) && !err)
+				err = device_create_file(f->dev, attr);
+		}
+		if (err) {
+			pr_err("%s: Failed to create function %s attributes",
+					__func__, f->name);
+			goto err_out;
+		}
+	}
+	return 0;
+
+err_out:
+	device_destroy(android_class, f->dev->devt);
+err_create:
+	kfree(f->dev_name);
+	return err;
+}
+
+static void android_cleanup_functions(struct android_usb_function **functions)
+{
+	struct android_usb_function *f;
+
+	while (*functions) {
+		f = *functions++;
+
+		if (f->dev) {
+			device_destroy(android_class, f->dev->devt);
+			kfree(f->dev_name);
+		}
+
+		if (f->cleanup)
+			f->cleanup(f);
+	}
+}
+
+static int
+android_bind_enabled_functions(struct android_dev *dev,
+			       struct usb_configuration *c)
+{
+	struct android_usb_function *f;
+	int ret;
+
+	list_for_each_entry(f, &dev->enabled_functions, enabled_list) {
+		ret = f->bind_config(f, c);
+		if (ret) {
+			pr_err("%s: %s failed", __func__, f->name);
+			return ret;
+		}
+	}
+	return 0;
+}
+
+static void
+android_unbind_enabled_functions(struct android_dev *dev,
+			       struct usb_configuration *c)
+{
+	struct android_usb_function *f;
+
+	list_for_each_entry(f, &dev->enabled_functions, enabled_list) {
+		if (f->unbind_config)
+			f->unbind_config(f, c);
+	}
+}
+
+static int android_enable_function(struct android_dev *dev, char *name)
+{
+	struct android_usb_function **functions = dev->functions;
+	struct android_usb_function *f;
+	while ((f = *functions++)) {
+		if (!strcmp(name, f->name)) {
+			list_add_tail(&f->enabled_list,
+						&dev->enabled_functions);
+			return 0;
+		}
+	}
+	return -EINVAL;
+}
+
+/*-------------------------------------------------------------------------*/
+/* /sys/class/android_usb/android%d/ interface */
+
+static ssize_t
+functions_show(struct device *pdev, struct device_attribute *attr, char *buf)
+{
+	struct android_dev *dev = dev_get_drvdata(pdev);
+	struct android_usb_function *f;
+	char *buff = buf;
+
+	mutex_lock(&dev->mutex);
+
+	list_for_each_entry(f, &dev->enabled_functions, enabled_list)
+		buff += sprintf(buff, "%s,", f->name);
+
+	mutex_unlock(&dev->mutex);
+
+	if (buff != buf)
+		*(buff-1) = '\n';
+	return buff - buf;
+}
+
+static ssize_t
+functions_store(struct device *pdev, struct device_attribute *attr,
+			       const char *buff, size_t size)
+{
+	struct android_dev *dev = dev_get_drvdata(pdev);
+	char *name;
+	char buf[256], *b;
+	int err;
+
+	mutex_lock(&dev->mutex);
+
+	if (dev->enabled) {
+		mutex_unlock(&dev->mutex);
+		return -EBUSY;
+	}
+
+	INIT_LIST_HEAD(&dev->enabled_functions);
+
+	strncpy(buf, buff, sizeof(buf));
+	b = strim(buf);
+
+	while (b) {
+		name = strsep(&b, ",");
+		if (name) {
+			err = android_enable_function(dev, name);
+			if (err)
+				pr_err("android_usb: Cannot enable '%s'", name);
+		}
+	}
+
+	mutex_unlock(&dev->mutex);
+
+	return size;
+}
+
+static ssize_t enable_show(struct device *pdev, struct device_attribute *attr,
+			   char *buf)
+{
+	struct android_dev *dev = dev_get_drvdata(pdev);
+	return sprintf(buf, "%d\n", dev->enabled);
+}
+
+static ssize_t enable_store(struct device *pdev, struct device_attribute *attr,
+			    const char *buff, size_t size)
+{
+	struct android_dev *dev = dev_get_drvdata(pdev);
+	struct usb_composite_dev *cdev = dev->cdev;
+	int enabled = 0;
+
+	mutex_lock(&dev->mutex);
+
+	sscanf(buff, "%d", &enabled);
+	if (enabled && !dev->enabled) {
+		cdev->next_string_id = 0;
+		/*
+		 * Update values in composite driver's copy of
+		 * device descriptor.
+		 */
+		cdev->desc.idVendor = device_desc.idVendor;
+		cdev->desc.idProduct = device_desc.idProduct;
+		cdev->desc.bcdDevice = device_desc.bcdDevice;
+		cdev->desc.bDeviceClass = device_desc.bDeviceClass;
+		cdev->desc.bDeviceSubClass = device_desc.bDeviceSubClass;
+		cdev->desc.bDeviceProtocol = device_desc.bDeviceProtocol;
+
+		usb_add_config(cdev, &android_config_driver,
+					android_bind_config);
+		usb_gadget_connect(cdev->gadget);
+		dev->enabled = true;
+	} else if (!enabled && dev->enabled) {
+		usb_gadget_disconnect(cdev->gadget);
+		/* Cancel pending control requests */
+		usb_ep_dequeue(cdev->gadget->ep0, cdev->req);
+		usb_remove_config(cdev, &android_config_driver);
+		dev->enabled = false;
+	} else {
+		pr_err("android_usb: already %s\n",
+				dev->enabled ? "enabled" : "disabled");
+	}
+
+	mutex_unlock(&dev->mutex);
+	return size;
+}
+
+static ssize_t state_show(struct device *pdev, struct device_attribute *attr,
+			   char *buf)
+{
+	struct android_dev *dev = dev_get_drvdata(pdev);
+	struct usb_composite_dev *cdev = dev->cdev;
+	char *state = "DISCONNECTED";
+	unsigned long flags;
+
+	if (!cdev)
+		goto out;
+
+	spin_lock_irqsave(&cdev->lock, flags);
+	if (cdev->config)
+		state = "CONFIGURED";
+	else if (dev->connected)
+		state = "CONNECTED";
+	spin_unlock_irqrestore(&cdev->lock, flags);
+out:
+	return sprintf(buf, "%s\n", state);
+}
+
+#define DESCRIPTOR_ATTR(field, format_string)				\
+static ssize_t								\
+field ## _show(struct device *dev, struct device_attribute *attr,	\
+		char *buf)						\
+{									\
+	return sprintf(buf, format_string, device_desc.field);		\
+}									\
+static ssize_t								\
+field ## _store(struct device *dev, struct device_attribute *attr,	\
+		const char *buf, size_t size)				\
+{									\
+	int value;							\
+	if (sscanf(buf, format_string, &value) == 1) {			\
+		device_desc.field = value;				\
+		return size;						\
+	}								\
+	return -1;							\
+}									\
+static DEVICE_ATTR(field, S_IRUGO | S_IWUSR, field ## _show, field ## _store);
+
+#define DESCRIPTOR_STRING_ATTR(field, buffer)				\
+static ssize_t								\
+field ## _show(struct device *dev, struct device_attribute *attr,	\
+		char *buf)						\
+{									\
+	return sprintf(buf, "%s", buffer);				\
+}									\
+static ssize_t								\
+field ## _store(struct device *dev, struct device_attribute *attr,	\
+		const char *buf, size_t size)				\
+{									\
+	if (size >= sizeof(buffer))					\
+		return -EINVAL;						\
+	if (sscanf(buf, "%s", buffer) == 1) {				\
+		return size;						\
+	}								\
+	return -1;							\
+}									\
+static DEVICE_ATTR(field, S_IRUGO | S_IWUSR, field ## _show, field ## _store);
+
+
+DESCRIPTOR_ATTR(idVendor, "%04x\n")
+DESCRIPTOR_ATTR(idProduct, "%04x\n")
+DESCRIPTOR_ATTR(bcdDevice, "%04x\n")
+DESCRIPTOR_ATTR(bDeviceClass, "%d\n")
+DESCRIPTOR_ATTR(bDeviceSubClass, "%d\n")
+DESCRIPTOR_ATTR(bDeviceProtocol, "%d\n")
+DESCRIPTOR_STRING_ATTR(iManufacturer, manufacturer_string)
+DESCRIPTOR_STRING_ATTR(iProduct, product_string)
+DESCRIPTOR_STRING_ATTR(iSerial, serial_string)
+
+static DEVICE_ATTR(functions, S_IRUGO | S_IWUSR, functions_show,
+						 functions_store);
+static DEVICE_ATTR(enable, S_IRUGO | S_IWUSR, enable_show, enable_store);
+static DEVICE_ATTR(state, S_IRUGO, state_show, NULL);
+
+static struct device_attribute *android_usb_attributes[] = {
+	&dev_attr_idVendor,
+	&dev_attr_idProduct,
+	&dev_attr_bcdDevice,
+	&dev_attr_bDeviceClass,
+	&dev_attr_bDeviceSubClass,
+	&dev_attr_bDeviceProtocol,
+	&dev_attr_iManufacturer,
+	&dev_attr_iProduct,
+	&dev_attr_iSerial,
+	&dev_attr_functions,
+	&dev_attr_enable,
+	&dev_attr_state,
+	NULL
+};
+
+/*-------------------------------------------------------------------------*/
+/* Composite driver */
+
+static int android_bind_config(struct usb_configuration *c)
+{
+	struct android_dev *dev = _android_dev;
+	int ret = 0;
+
+	ret = android_bind_enabled_functions(dev, c);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+static void android_unbind_config(struct usb_configuration *c)
+{
+	struct android_dev *dev = _android_dev;
+
+	android_unbind_enabled_functions(dev, c);
+}
+
+static int android_bind(struct usb_composite_dev *cdev)
+{
+	struct android_dev *dev = _android_dev;
+	struct usb_gadget	*gadget = cdev->gadget;
+	int			gcnum, id, ret;
+
+	/*
+	 * Start disconnected. Userspace will connect the gadget once
+	 * it is done configuring the functions.
+	 */
+	usb_gadget_disconnect(gadget);
+
+	ret = android_init_functions(dev->functions, cdev);
+	if (ret)
+		return ret;
+
+	/* Allocate string descriptor numbers ... note that string
+	 * contents can be overridden by the composite_dev glue.
+	 */
+	id = usb_string_id(cdev);
+	if (id < 0)
+		return id;
+	strings_dev[STRING_MANUFACTURER_IDX].id = id;
+	device_desc.iManufacturer = id;
+
+	id = usb_string_id(cdev);
+	if (id < 0)
+		return id;
+	strings_dev[STRING_PRODUCT_IDX].id = id;
+	device_desc.iProduct = id;
+
+	/* Default strings - should be updated by userspace */
+	strncpy(manufacturer_string, "Android", sizeof(manufacturer_string)-1);
+	strncpy(product_string, "Android", sizeof(product_string) - 1);
+	strncpy(serial_string, "0123456789ABCDEF", sizeof(serial_string) - 1);
+
+	id = usb_string_id(cdev);
+	if (id < 0)
+		return id;
+	strings_dev[STRING_SERIAL_IDX].id = id;
+	device_desc.iSerialNumber = id;
+
+	gcnum = usb_gadget_controller_number(gadget);
+	if (gcnum >= 0)
+		device_desc.bcdDevice = cpu_to_le16(0x0200 + gcnum);
+	else {
+		pr_warning("%s: controller '%s' not recognized\n",
+			longname, gadget->name);
+		device_desc.bcdDevice = __constant_cpu_to_le16(0x9999);
+	}
+
+	usb_gadget_set_selfpowered(gadget);
+	dev->cdev = cdev;
+
+	return 0;
+}
+
+static int android_usb_unbind(struct usb_composite_dev *cdev)
+{
+	struct android_dev *dev = _android_dev;
+
+	cancel_work_sync(&dev->work);
+	android_cleanup_functions(dev->functions);
+	return 0;
+}
+
+static struct usb_composite_driver android_usb_driver = {
+	.name		= "android_usb",
+	.dev		= &device_desc,
+	.strings	= dev_strings,
+	.unbind		= android_usb_unbind,
+	.max_speed	= USB_SPEED_HIGH,
+};
+
+static int
+android_setup(struct usb_gadget *gadget, const struct usb_ctrlrequest *c)
+{
+	struct android_dev		*dev = _android_dev;
+	struct usb_composite_dev	*cdev = get_gadget_data(gadget);
+	struct usb_request		*req = cdev->req;
+	struct android_usb_function	*f;
+	int value = -EOPNOTSUPP;
+	unsigned long flags;
+
+	req->zero = 0;
+	req->complete = composite_setup_complete;
+	req->length = 0;
+	gadget->ep0->driver_data = cdev;
+
+	list_for_each_entry(f, &dev->enabled_functions, enabled_list) {
+		if (f->ctrlrequest) {
+			value = f->ctrlrequest(f, cdev, c);
+			if (value >= 0)
+				break;
+		}
+	}
+
+	if (value < 0)
+		value = composite_setup(gadget, c);
+
+	spin_lock_irqsave(&cdev->lock, flags);
+	if (!dev->connected) {
+		dev->connected = 1;
+		schedule_work(&dev->work);
+	} else if (c->bRequest == USB_REQ_SET_CONFIGURATION &&
+						cdev->config) {
+		schedule_work(&dev->work);
+	}
+	spin_unlock_irqrestore(&cdev->lock, flags);
+
+	return value;
+}
+
+static void android_disconnect(struct usb_gadget *gadget)
+{
+	struct android_dev *dev = _android_dev;
+	struct usb_composite_dev *cdev = get_gadget_data(gadget);
+	unsigned long flags;
+
+	composite_disconnect(gadget);
+
+	spin_lock_irqsave(&cdev->lock, flags);
+	dev->connected = 0;
+	schedule_work(&dev->work);
+	spin_unlock_irqrestore(&cdev->lock, flags);
+}
+
+static int android_create_device(struct android_dev *dev)
+{
+	struct device_attribute **attrs = android_usb_attributes;
+	struct device_attribute *attr;
+	int err;
+
+	dev->dev = device_create(android_class, NULL,
+					MKDEV(0, 0), NULL, "android0");
+	if (IS_ERR(dev->dev))
+		return PTR_ERR(dev->dev);
+
+	dev_set_drvdata(dev->dev, dev);
+
+	while ((attr = *attrs++)) {
+		err = device_create_file(dev->dev, attr);
+		if (err) {
+			device_destroy(android_class, dev->dev->devt);
+			return err;
+		}
+	}
+	return 0;
+}
+
+
+static int __init init(void)
+{
+	struct android_dev *dev;
+	int err;
+
+	android_class = class_create(THIS_MODULE, "android_usb");
+	if (IS_ERR(android_class))
+		return PTR_ERR(android_class);
+
+	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
+	if (!dev)
+		return -ENOMEM;
+
+	dev->functions = supported_functions;
+	INIT_LIST_HEAD(&dev->enabled_functions);
+	INIT_WORK(&dev->work, android_work);
+	mutex_init(&dev->mutex);
+
+	err = android_create_device(dev);
+	if (err) {
+		class_destroy(android_class);
+		kfree(dev);
+		return err;
+	}
+
+	_android_dev = dev;
+
+	/* Override composite driver functions */
+	composite_driver.setup = android_setup;
+	composite_driver.disconnect = android_disconnect;
+
+	return usb_composite_probe(&android_usb_driver, android_bind);
+}
+module_init(init);
+
+static void __exit cleanup(void)
+{
+	usb_composite_unregister(&android_usb_driver);
+	class_destroy(android_class);
+	kfree(_android_dev);
+	_android_dev = NULL;
+}
+module_exit(cleanup);