usb gadget: composite gadget core

Add <linux/usb/composite.h> interfaces for composite gadget drivers, and
basic implementation support behind it:

  - struct usb_function ... groups one or more interfaces into a function
    managed as one unit within a configuration, to which it's added by
    usb_add_function().

  - struct usb_configuration ... groups one or more such functions into
    a configuration managed as one unit by a driver, to which it's added
    by usb_add_config().  These operate at either high or full/low speeds
    and at a given bMaxPower.

  - struct usb_composite_driver ... groups one or more such configurations
    into a gadget driver, which may be registered or unregistered.

  - struct usb_composite_dev ... a usb_composite_driver manages this; it
    wraps the usb_gadget exposed by the controller driver.

This also includes some basic kerneldoc.

How to use it (the short version):  provide a usb_composite_driver with a
bind() that calls usb_add_config() for each of the needed configurations.
The configurations in turn have bind() calls, which will usb_add_function()
for each function required.  Each function's bind() allocates resources
needed to perform its tasks, like endpoints; sometimes configurations will
allocate resources too.

Separate patches will convert most gadget drivers to this infrastructure.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 1040 insertions, 0 deletions

diff --git a/drivers/usb/gadget/composite.c b/drivers/usb/gadget/composite.c
new file mode 100644
index 0000000..b3d302a
--- /dev/null
+++ b/drivers/usb/gadget/composite.c
@@ -0,0 +1,1040 @@
+/*
+ * composite.c - infrastructure for Composite USB Gadgets
+ *
+ * Copyright (C) 2006-2008 David Brownell
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * 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.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+/* #define VERBOSE_DEBUG */
+
+#include <linux/kallsyms.h>
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/device.h>
+
+#include <linux/usb/composite.h>
+
+
+/*
+ * The code in this file is utility code, used to build a gadget driver
+ * from one or more "function" drivers, one or more "configuration"
+ * objects, and a "usb_composite_driver" by gluing them together along
+ * with the relevant device-wide data.
+ */
+
+/* big enough to hold our biggest descriptor */
+#define USB_BUFSIZ	512
+
+static struct usb_composite_driver *composite;
+
+/* Some systems will need runtime overrides for the  product identifers
+ * published in the device descriptor, either numbers or strings or both.
+ * String parameters are in UTF-8 (superset of ASCII's 7 bit characters).
+ */
+
+static ushort idVendor;
+module_param(idVendor, ushort, 0);
+MODULE_PARM_DESC(idVendor, "USB Vendor ID");
+
+static ushort idProduct;
+module_param(idProduct, ushort, 0);
+MODULE_PARM_DESC(idProduct, "USB Product ID");
+
+static ushort bcdDevice;
+module_param(bcdDevice, ushort, 0);
+MODULE_PARM_DESC(bcdDevice, "USB Device version (BCD)");
+
+static char *iManufacturer;
+module_param(iManufacturer, charp, 0);
+MODULE_PARM_DESC(iManufacturer, "USB Manufacturer string");
+
+static char *iProduct;
+module_param(iProduct, charp, 0);
+MODULE_PARM_DESC(iProduct, "USB Product string");
+
+static char *iSerialNumber;
+module_param(iSerialNumber, charp, 0);
+MODULE_PARM_DESC(iSerialNumber, "SerialNumber string");
+
+/*-------------------------------------------------------------------------*/
+
+/**
+ * usb_add_function() - add a function to a configuration
+ * @config: the configuration
+ * @function: the function being added
+ * Context: single threaded during gadget setup
+ *
+ * After initialization, each configuration must have one or more
+ * functions added to it.  Adding a function involves calling its @bind()
+ * method to allocate resources such as interface and string identifiers
+ * and endpoints.
+ *
+ * This function returns the value of the function's bind(), which is
+ * zero for success else a negative errno value.
+ */
+int __init usb_add_function(struct usb_configuration *config,
+		struct usb_function *function)
+{
+	int	value = -EINVAL;
+
+	DBG(config->cdev, "adding '%s'/%p to config '%s'/%p\n",
+			function->name, function,
+			config->label, config);
+
+	if (!function->set_alt || !function->disable)
+		goto done;
+
+	function->config = config;
+	list_add_tail(&function->list, &config->functions);
+
+	/* REVISIT *require* function->bind? */
+	if (function->bind) {
+		value = function->bind(config, function);
+		if (value < 0) {
+			list_del(&function->list);
+			function->config = NULL;
+		}
+	} else
+		value = 0;
+
+	/* We allow configurations that don't work at both speeds.
+	 * If we run into a lowspeed Linux system, treat it the same
+	 * as full speed ... it's the function drivers that will need
+	 * to avoid bulk and ISO transfers.
+	 */
+	if (!config->fullspeed && function->descriptors)
+		config->fullspeed = true;
+	if (!config->highspeed && function->hs_descriptors)
+		config->highspeed = true;
+
+done:
+	if (value)
+		DBG(config->cdev, "adding '%s'/%p --> %d\n",
+				function->name, function, value);
+	return value;
+}
+
+/**
+ * usb_interface_id() - allocate an unused interface ID
+ * @config: configuration associated with the interface
+ * @function: function handling the interface
+ * Context: single threaded during gadget setup
+ *
+ * usb_interface_id() is called from usb_function.bind() callbacks to
+ * allocate new interface IDs.  The function driver will then store that
+ * ID in interface, association, CDC union, and other descriptors.  It
+ * will also handle any control requests targetted at that interface,
+ * particularly changing its altsetting via set_alt().  There may
+ * also be class-specific or vendor-specific requests to handle.
+ *
+ * All interface identifier should be allocated using this routine, to
+ * ensure that for example different functions don't wrongly assign
+ * different meanings to the same identifier.  Note that since interface
+ * identifers are configuration-specific, functions used in more than
+ * one configuration (or more than once in a given configuration) need
+ * multiple versions of the relevant descriptors.
+ *
+ * Returns the interface ID which was allocated; or -ENODEV if no
+ * more interface IDs can be allocated.
+ */
+int __init usb_interface_id(struct usb_configuration *config,
+		struct usb_function *function)
+{
+	unsigned id = config->next_interface_id;
+
+	if (id < MAX_CONFIG_INTERFACES) {
+		config->interface[id] = function;
+		config->next_interface_id = id + 1;
+		return id;
+	}
+	return -ENODEV;
+}
+
+static int config_buf(struct usb_configuration *config,
+		enum usb_device_speed speed, void *buf, u8 type)
+{
+	struct usb_config_descriptor	*c = buf;
+	void				*next = buf + USB_DT_CONFIG_SIZE;
+	int				len = USB_BUFSIZ - USB_DT_CONFIG_SIZE;
+	struct usb_function		*f;
+	int				status;
+
+	/* write the config descriptor */
+	c = buf;
+	c->bLength = USB_DT_CONFIG_SIZE;
+	c->bDescriptorType = type;
+	/* wTotalLength is written later */
+	c->bNumInterfaces = config->next_interface_id;
+	c->bConfigurationValue = config->bConfigurationValue;
+	c->iConfiguration = config->iConfiguration;
+	c->bmAttributes = USB_CONFIG_ATT_ONE | config->bmAttributes;
+	c->bMaxPower = config->bMaxPower;
+
+	/* There may be e.g. OTG descriptors */
+	if (config->descriptors) {
+		status = usb_descriptor_fillbuf(next, len,
+				config->descriptors);
+		if (status < 0)
+			return status;
+		len -= status;
+		next += status;
+	}
+
+	/* add each function's descriptors */
+	list_for_each_entry(f, &config->functions, list) {
+		struct usb_descriptor_header **descriptors;
+
+		if (speed == USB_SPEED_HIGH)
+			descriptors = f->hs_descriptors;
+		else
+			descriptors = f->descriptors;
+		if (!descriptors)
+			continue;
+		status = usb_descriptor_fillbuf(next, len,
+			(const struct usb_descriptor_header **) descriptors);
+		if (status < 0)
+			return status;
+		len -= status;
+		next += status;
+	}
+
+	len = next - buf;
+	c->wTotalLength = cpu_to_le16(len);
+	return len;
+}
+
+static int config_desc(struct usb_composite_dev *cdev, unsigned w_value)
+{
+	struct usb_gadget		*gadget = cdev->gadget;
+	struct usb_configuration	*c;
+	u8				type = w_value >> 8;
+	enum usb_device_speed		speed = USB_SPEED_UNKNOWN;
+
+	if (gadget_is_dualspeed(gadget)) {
+		int			hs = 0;
+
+		if (gadget->speed == USB_SPEED_HIGH)
+			hs = 1;
+		if (type == USB_DT_OTHER_SPEED_CONFIG)
+			hs = !hs;
+		if (hs)
+			speed = USB_SPEED_HIGH;
+
+	}
+
+	/* This is a lookup by config *INDEX* */
+	w_value &= 0xff;
+	list_for_each_entry(c, &cdev->configs, list) {
+		/* ignore configs that won't work at this speed */
+		if (speed == USB_SPEED_HIGH) {
+			if (!c->highspeed)
+				continue;
+		} else {
+			if (!c->fullspeed)
+				continue;
+		}
+		if (w_value == 0)
+			return config_buf(c, speed, cdev->req->buf, type);
+		w_value--;
+	}
+	return -EINVAL;
+}
+
+static int count_configs(struct usb_composite_dev *cdev, unsigned type)
+{
+	struct usb_gadget		*gadget = cdev->gadget;
+	struct usb_configuration	*c;
+	unsigned			count = 0;
+	int				hs = 0;
+
+	if (gadget_is_dualspeed(gadget)) {
+		if (gadget->speed == USB_SPEED_HIGH)
+			hs = 1;
+		if (type == USB_DT_DEVICE_QUALIFIER)
+			hs = !hs;
+	}
+	list_for_each_entry(c, &cdev->configs, list) {
+		/* ignore configs that won't work at this speed */
+		if (hs) {
+			if (!c->highspeed)
+				continue;
+		} else {
+			if (!c->fullspeed)
+				continue;
+		}
+		count++;
+	}
+	return count;
+}
+
+static void device_qual(struct usb_composite_dev *cdev)
+{
+	struct usb_qualifier_descriptor	*qual = cdev->req->buf;
+
+	qual->bLength = sizeof(*qual);
+	qual->bDescriptorType = USB_DT_DEVICE_QUALIFIER;
+	/* POLICY: same bcdUSB and device type info at both speeds */
+	qual->bcdUSB = cdev->desc.bcdUSB;
+	qual->bDeviceClass = cdev->desc.bDeviceClass;
+	qual->bDeviceSubClass = cdev->desc.bDeviceSubClass;
+	qual->bDeviceProtocol = cdev->desc.bDeviceProtocol;
+	/* ASSUME same EP0 fifo size at both speeds */
+	qual->bMaxPacketSize0 = cdev->desc.bMaxPacketSize0;
+	qual->bNumConfigurations = count_configs(cdev, USB_DT_DEVICE_QUALIFIER);
+}
+
+/*-------------------------------------------------------------------------*/
+
+static void reset_config(struct usb_composite_dev *cdev)
+{
+	struct usb_function		*f;
+
+	DBG(cdev, "reset config\n");
+
+	list_for_each_entry(f, &cdev->config->functions, list) {
+		if (f->disable)
+			f->disable(f);
+	}
+	cdev->config = NULL;
+}
+
+static int set_config(struct usb_composite_dev *cdev,
+		const struct usb_ctrlrequest *ctrl, unsigned number)
+{
+	struct usb_gadget	*gadget = cdev->gadget;
+	struct usb_configuration *c = NULL;
+	int			result = -EINVAL;
+	unsigned		power = gadget_is_otg(gadget) ? 8 : 100;
+	int			tmp;
+
+	if (cdev->config)
+		reset_config(cdev);
+
+	if (number) {
+		list_for_each_entry(c, &cdev->configs, list) {
+			if (c->bConfigurationValue == number) {
+				result = 0;
+				break;
+			}
+		}
+		if (result < 0)
+			goto done;
+	} else
+		result = 0;
+
+	INFO(cdev, "%s speed config #%d: %s\n",
+		({ char *speed;
+		switch (gadget->speed) {
+		case USB_SPEED_LOW:	speed = "low"; break;
+		case USB_SPEED_FULL:	speed = "full"; break;
+		case USB_SPEED_HIGH:	speed = "high"; break;
+		default:		speed = "?"; break;
+		} ; speed; }), number, c ? c->label : "unconfigured");
+
+	if (!c)
+		goto done;
+
+	cdev->config = c;
+
+	/* Initialize all interfaces by setting them to altsetting zero. */
+	for (tmp = 0; tmp < MAX_CONFIG_INTERFACES; tmp++) {
+		struct usb_function	*f = c->interface[tmp];
+
+		if (!f)
+			break;
+
+		result = f->set_alt(f, tmp, 0);
+		if (result < 0) {
+			DBG(cdev, "interface %d (%s/%p) alt 0 --> %d\n",
+					tmp, f->name, f, result);
+
+			reset_config(cdev);
+			goto done;
+		}
+	}
+
+	/* when we return, be sure our power usage is valid */
+	power = 2 * c->bMaxPower;
+done:
+	usb_gadget_vbus_draw(gadget, power);
+	return result;
+}
+
+/**
+ * usb_add_config() - add a configuration to a device.
+ * @cdev: wraps the USB gadget
+ * @config: the configuration, with bConfigurationValue assigned
+ * Context: single threaded during gadget setup
+ *
+ * One of the main tasks of a composite driver's bind() routine is to
+ * add each of the configurations it supports, using this routine.
+ *
+ * This function returns the value of the configuration's bind(), which
+ * is zero for success else a negative errno value.  Binding configurations
+ * assigns global resources including string IDs, and per-configuration
+ * resources such as interface IDs and endpoints.
+ */
+int __init usb_add_config(struct usb_composite_dev *cdev,
+		struct usb_configuration *config)
+{
+	int				status = -EINVAL;
+	struct usb_configuration	*c;
+
+	DBG(cdev, "adding config #%u '%s'/%p\n",
+			config->bConfigurationValue,
+			config->label, config);
+
+	if (!config->bConfigurationValue || !config->bind)
+		goto done;
+
+	/* Prevent duplicate configuration identifiers */
+	list_for_each_entry(c, &cdev->configs, list) {
+		if (c->bConfigurationValue == config->bConfigurationValue) {
+			status = -EBUSY;
+			goto done;
+		}
+	}
+
+	config->cdev = cdev;
+	list_add_tail(&config->list, &cdev->configs);
+
+	INIT_LIST_HEAD(&config->functions);
+	config->next_interface_id = 0;
+
+	status = config->bind(config);
+	if (status < 0) {
+		list_del(&config->list);
+		config->cdev = NULL;
+	} else {
+		unsigned	i;
+
+		DBG(cdev, "cfg %d/%p speeds:%s%s\n",
+			config->bConfigurationValue, config,
+			config->highspeed ? " high" : "",
+			config->fullspeed
+				? (gadget_is_dualspeed(cdev->gadget)
+					? " full"
+					: " full/low")
+				: "");
+
+		for (i = 0; i < MAX_CONFIG_INTERFACES; i++) {
+			struct usb_function	*f = config->interface[i];
+
+			if (!f)
+				continue;
+			DBG(cdev, "  interface %d = %s/%p\n",
+				i, f->name, f);
+		}
+	}
+
+	/* set_alt(), or next config->bind(), sets up
+	 * ep->driver_data as needed.
+	 */
+	usb_ep_autoconfig_reset(cdev->gadget);
+
+done:
+	if (status)
+		DBG(cdev, "added config '%s'/%u --> %d\n", config->label,
+				config->bConfigurationValue, status);
+	return status;
+}
+
+/*-------------------------------------------------------------------------*/
+
+/* We support strings in multiple languages ... string descriptor zero
+ * says which languages are supported.  The typical case will be that
+ * only one language (probably English) is used, with I18N handled on
+ * the host side.
+ */
+
+static void collect_langs(struct usb_gadget_strings **sp, __le16 *buf)
+{
+	const struct usb_gadget_strings	*s;
+	u16				language;
+	__le16				*tmp;
+
+	while (*sp) {
+		s = *sp;
+		language = cpu_to_le16(s->language);
+		for (tmp = buf; *tmp && tmp < &buf[126]; tmp++) {
+			if (*tmp == language)
+				goto repeat;
+		}
+		*tmp++ = language;
+repeat:
+		sp++;
+	}
+}
+
+static int lookup_string(
+	struct usb_gadget_strings	**sp,
+	void				*buf,
+	u16				language,
+	int				id
+)
+{
+	struct usb_gadget_strings	*s;
+	int				value;
+
+	while (*sp) {
+		s = *sp++;
+		if (s->language != language)
+			continue;
+		value = usb_gadget_get_string(s, id, buf);
+		if (value > 0)
+			return value;
+	}
+	return -EINVAL;
+}
+
+static int get_string(struct usb_composite_dev *cdev,
+		void *buf, u16 language, int id)
+{
+	struct usb_configuration	*c;
+	struct usb_function		*f;
+	int				len;
+
+	/* Yes, not only is USB's I18N support probably more than most
+	 * folk will ever care about ... also, it's all supported here.
+	 * (Except for UTF8 support for Unicode's "Astral Planes".)
+	 */
+
+	/* 0 == report all available language codes */
+	if (id == 0) {
+		struct usb_string_descriptor	*s = buf;
+		struct usb_gadget_strings	**sp;
+
+		memset(s, 0, 256);
+		s->bDescriptorType = USB_DT_STRING;
+
+		sp = composite->strings;
+		if (sp)
+			collect_langs(sp, s->wData);
+
+		list_for_each_entry(c, &cdev->configs, list) {
+			sp = c->strings;
+			if (sp)
+				collect_langs(sp, s->wData);
+
+			list_for_each_entry(f, &c->functions, list) {
+				sp = f->strings;
+				if (sp)
+					collect_langs(sp, s->wData);
+			}
+		}
+
+		for (len = 0; s->wData[len] && len <= 126; len++)
+			continue;
+		if (!len)
+			return -EINVAL;
+
+		s->bLength = 2 * (len + 1);
+		return s->bLength;
+	}
+
+	/* Otherwise, look up and return a specified string.  String IDs
+	 * are device-scoped, so we look up each string table we're told
+	 * about.  These lookups are infrequent; simpler-is-better here.
+	 */
+	if (composite->strings) {
+		len = lookup_string(composite->strings, buf, language, id);
+		if (len > 0)
+			return len;
+	}
+	list_for_each_entry(c, &cdev->configs, list) {
+		if (c->strings) {
+			len = lookup_string(c->strings, buf, language, id);
+			if (len > 0)
+				return len;
+		}
+		list_for_each_entry(f, &c->functions, list) {
+			if (!f->strings)
+				continue;
+			len = lookup_string(f->strings, buf, language, id);
+			if (len > 0)
+				return len;
+		}
+	}
+	return -EINVAL;
+}
+
+/**
+ * usb_string_id() - allocate an unused string ID
+ * @cdev: the device whose string descriptor IDs are being allocated
+ * Context: single threaded during gadget setup
+ *
+ * @usb_string_id() is called from bind() callbacks to allocate
+ * string IDs.  Drivers for functions, configurations, or gadgets will
+ * then store that ID in the appropriate descriptors and string table.
+ *
+ * All string identifier should be allocated using this routine, to
+ * ensure that for example different functions don't wrongly assign
+ * different meanings to the same identifier.
+ */
+int __init usb_string_id(struct usb_composite_dev *cdev)
+{
+	if (cdev->next_string_id < 254) {
+		/* string id 0 is reserved */
+		cdev->next_string_id++;
+		return cdev->next_string_id;
+	}
+	return -ENODEV;
+}
+
+/*-------------------------------------------------------------------------*/
+
+static void composite_setup_complete(struct usb_ep *ep, struct usb_request *req)
+{
+	if (req->status || req->actual != req->length)
+		DBG((struct usb_composite_dev *) ep->driver_data,
+				"setup complete --> %d, %d/%d\n",
+				req->status, req->actual, req->length);
+}
+
+/*
+ * The setup() callback implements all the ep0 functionality that's
+ * not handled lower down, in hardware or the hardware driver(like
+ * device and endpoint feature flags, and their status).  It's all
+ * housekeeping for the gadget function we're implementing.  Most of
+ * the work is in config and function specific setup.
+ */
+static int
+composite_setup(struct usb_gadget *gadget, const struct usb_ctrlrequest *ctrl)
+{
+	struct usb_composite_dev	*cdev = get_gadget_data(gadget);
+	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);
+	struct usb_function		*f = NULL;
+
+	/* partial re-init of the response message; the function or the
+	 * gadget might need to intercept e.g. a control-OUT completion
+	 * when we delegate to it.
+	 */
+	req->zero = 0;
+	req->complete = composite_setup_complete;
+	req->length = USB_BUFSIZ;
+	gadget->ep0->driver_data = cdev;
+
+	switch (ctrl->bRequest) {
+
+	/* we handle all standard USB descriptors */
+	case USB_REQ_GET_DESCRIPTOR:
+		if (ctrl->bRequestType != USB_DIR_IN)
+			goto unknown;
+		switch (w_value >> 8) {
+
+		case USB_DT_DEVICE:
+			cdev->desc.bNumConfigurations =
+				count_configs(cdev, USB_DT_DEVICE);
+			value = min(w_length, (u16) sizeof cdev->desc);
+			memcpy(req->buf, &cdev->desc, value);
+			break;
+		case USB_DT_DEVICE_QUALIFIER:
+			if (!gadget_is_dualspeed(gadget))
+				break;
+			device_qual(cdev);
+			value = min_t(int, w_length,
+				sizeof(struct usb_qualifier_descriptor));
+			break;
+		case USB_DT_OTHER_SPEED_CONFIG:
+			if (!gadget_is_dualspeed(gadget))
+				break;
+			/* FALLTHROUGH */
+		case USB_DT_CONFIG:
+			value = config_desc(cdev, w_value);
+			if (value >= 0)
+				value = min(w_length, (u16) value);
+			break;
+		case USB_DT_STRING:
+			value = get_string(cdev, req->buf,
+					w_index, w_value & 0xff);
+			if (value >= 0)
+				value = min(w_length, (u16) value);
+			break;
+		}
+		break;
+
+	/* any number of configs can work */
+	case USB_REQ_SET_CONFIGURATION:
+		if (ctrl->bRequestType != 0)
+			goto unknown;
+		if (gadget_is_otg(gadget)) {
+			if (gadget->a_hnp_support)
+				DBG(cdev, "HNP available\n");
+			else if (gadget->a_alt_hnp_support)
+				DBG(cdev, "HNP on another port\n");
+			else
+				VDBG(cdev, "HNP inactive\n");
+		}
+		spin_lock(&cdev->lock);
+		value = set_config(cdev, ctrl, w_value);
+		spin_unlock(&cdev->lock);
+		break;
+	case USB_REQ_GET_CONFIGURATION:
+		if (ctrl->bRequestType != USB_DIR_IN)
+			goto unknown;
+		if (cdev->config)
+			*(u8 *)req->buf = cdev->config->bConfigurationValue;
+		else
+			*(u8 *)req->buf = 0;
+		value = min(w_length, (u16) 1);
+		break;
+
+	/* function drivers must handle get/set altsetting; if there's
+	 * no get() method, we know only altsetting zero works.
+	 */
+	case USB_REQ_SET_INTERFACE:
+		if (ctrl->bRequestType != USB_RECIP_INTERFACE)
+			goto unknown;
+		if (!cdev->config || w_index >= MAX_CONFIG_INTERFACES)
+			break;
+		f = cdev->config->interface[w_index];
+		if (!f)
+			break;
+		if (w_value && !f->get_alt)
+			break;
+		value = f->set_alt(f, w_index, w_value);
+		break;
+	case USB_REQ_GET_INTERFACE:
+		if (ctrl->bRequestType != (USB_DIR_IN|USB_RECIP_INTERFACE))
+			goto unknown;
+		if (!cdev->config || w_index >= MAX_CONFIG_INTERFACES)
+			break;
+		f = cdev->config->interface[w_index];
+		if (!f)
+			break;
+		/* lots of interfaces only need altsetting zero... */
+		value = f->get_alt ? f->get_alt(f, w_index) : 0;
+		if (value < 0)
+			break;
+		*((u8 *)req->buf) = value;
+		value = min(w_length, (u16) 1);
+		break;
+	default:
+unknown:
+		VDBG(cdev,
+			"non-core control req%02x.%02x v%04x i%04x l%d\n",
+			ctrl->bRequestType, ctrl->bRequest,
+			w_value, w_index, w_length);
+
+		/* functions always handle their interfaces ... punt other
+		 * recipients (endpoint, other, WUSB, ...) to the current
+		 * configuration code.
+		 *
+		 * REVISIT it could make sense to let the composite device
+		 * take such requests too, if that's ever needed:  to work
+		 * in config 0, etc.
+		 */
+		if ((ctrl->bRequestType & USB_RECIP_MASK)
+				== USB_RECIP_INTERFACE) {
+			f = cdev->config->interface[w_index];
+			if (f && f->setup)
+				value = f->setup(f, ctrl);
+			else
+				f = NULL;
+		}
+		if (value < 0 && !f) {
+			struct usb_configuration	*c;
+
+			c = cdev->config;
+			if (c && c->setup)
+				value = c->setup(c, ctrl);
+		}
+
+		goto done;
+	}
+
+	/* respond with data transfer before status phase? */
+	if (value >= 0) {
+		req->length = value;
+		req->zero = value < w_length;
+		value = usb_ep_queue(gadget->ep0, req, GFP_ATOMIC);
+		if (value < 0) {
+			DBG(cdev, "ep_queue --> %d\n", value);
+			req->status = 0;
+			composite_setup_complete(gadget->ep0, req);
+		}
+	}
+
+done:
+	/* device either stalls (value < 0) or reports success */
+	return value;
+}
+
+static void composite_disconnect(struct usb_gadget *gadget)
+{
+	struct usb_composite_dev	*cdev = get_gadget_data(gadget);
+	unsigned long			flags;
+
+	/* REVISIT:  should we have config and device level
+	 * disconnect callbacks?
+	 */
+	spin_lock_irqsave(&cdev->lock, flags);
+	if (cdev->config)
+		reset_config(cdev);
+	spin_unlock_irqrestore(&cdev->lock, flags);
+}
+
+/*-------------------------------------------------------------------------*/
+
+static void /* __init_or_exit */
+composite_unbind(struct usb_gadget *gadget)
+{
+	struct usb_composite_dev	*cdev = get_gadget_data(gadget);
+
+	/* composite_disconnect() must already have been called
+	 * by the underlying peripheral controller driver!
+	 * so there's no i/o concurrency that could affect the
+	 * state protected by cdev->lock.
+	 */
+	WARN_ON(cdev->config);
+
+	while (!list_empty(&cdev->configs)) {
+		struct usb_configuration	*c;
+
+		c = list_first_entry(&cdev->configs,
+				struct usb_configuration, list);
+		while (!list_empty(&c->functions)) {
+			struct usb_function		*f;
+
+			f = list_first_entry(&c->functions,
+					struct usb_function, list);
+			list_del(&f->list);
+			if (f->unbind) {
+				DBG(cdev, "unbind function '%s'/%p\n",
+						f->name, f);
+				f->unbind(c, f);
+				/* may free memory for "f" */
+			}
+		}
+		list_del(&c->list);
+		if (c->unbind) {
+			DBG(cdev, "unbind config '%s'/%p\n", c->label, c);
+			c->unbind(c);
+			/* may free memory for "c" */
+		}
+	}
+	if (composite->unbind)
+		composite->unbind(cdev);
+
+	if (cdev->req) {
+		kfree(cdev->req->buf);
+		usb_ep_free_request(gadget->ep0, cdev->req);
+	}
+	kfree(cdev);
+	set_gadget_data(gadget, NULL);
+	composite = NULL;
+}
+
+static void __init
+string_override_one(struct usb_gadget_strings *tab, u8 id, const char *s)
+{
+	struct usb_string		*str = tab->strings;
+
+	for (str = tab->strings; str->s; str++) {
+		if (str->id == id) {
+			str->s = s;
+			return;
+		}
+	}
+}
+
+static void __init
+string_override(struct usb_gadget_strings **tab, u8 id, const char *s)
+{
+	while (*tab) {
+		string_override_one(*tab, id, s);
+		tab++;
+	}
+}
+
+static int __init composite_bind(struct usb_gadget *gadget)
+{
+	struct usb_composite_dev	*cdev;
+	int				status = -ENOMEM;
+
+	cdev = kzalloc(sizeof *cdev, GFP_KERNEL);
+	if (!cdev)
+		return status;
+
+	spin_lock_init(&cdev->lock);
+	cdev->gadget = gadget;
+	set_gadget_data(gadget, cdev);
+	INIT_LIST_HEAD(&cdev->configs);
+
+	/* preallocate control response and buffer */
+	cdev->req = usb_ep_alloc_request(gadget->ep0, GFP_KERNEL);
+	if (!cdev->req)
+		goto fail;
+	cdev->req->buf = kmalloc(USB_BUFSIZ, GFP_KERNEL);
+	if (!cdev->req->buf)
+		goto fail;
+	cdev->req->complete = composite_setup_complete;
+	gadget->ep0->driver_data = cdev;
+
+	cdev->bufsiz = USB_BUFSIZ;
+	cdev->driver = composite;
+
+	usb_gadget_set_selfpowered(gadget);
+
+	/* interface and string IDs start at zero via kzalloc.
+	 * we force endpoints to start unassigned; few controller
+	 * drivers will zero ep->driver_data.
+	 */
+	usb_ep_autoconfig_reset(cdev->gadget);
+
+	/* composite gadget needs to assign strings for whole device (like
+	 * serial number), register function drivers, potentially update
+	 * power state and consumption, etc
+	 */
+	status = composite->bind(cdev);
+	if (status < 0)
+		goto fail;
+
+	cdev->desc = *composite->dev;
+	cdev->desc.bMaxPacketSize0 = gadget->ep0->maxpacket;
+
+	/* standardized runtime overrides for device ID data */
+	if (idVendor)
+		cdev->desc.idVendor = cpu_to_le16(idVendor);
+	if (idProduct)
+		cdev->desc.idProduct = cpu_to_le16(idProduct);
+	if (bcdDevice)
+		cdev->desc.bcdDevice = cpu_to_le16(bcdDevice);
+
+	/* strings can't be assigned before bind() allocates the
+	 * releavnt identifiers
+	 */
+	if (cdev->desc.iManufacturer && iManufacturer)
+		string_override(composite->strings,
+			cdev->desc.iManufacturer, iManufacturer);
+	if (cdev->desc.iProduct && iProduct)
+		string_override(composite->strings,
+			cdev->desc.iProduct, iProduct);
+	if (cdev->desc.iSerialNumber && iSerialNumber)
+		string_override(composite->strings,
+			cdev->desc.iSerialNumber, iSerialNumber);
+
+	INFO(cdev, "%s ready\n", composite->name);
+	return 0;
+
+fail:
+	composite_unbind(gadget);
+	return status;
+}
+
+/*-------------------------------------------------------------------------*/
+
+static void
+composite_suspend(struct usb_gadget *gadget)
+{
+	struct usb_composite_dev	*cdev = get_gadget_data(gadget);
+	struct usb_function		*f;
+
+	/* REVISIT:  should we have config and device level
+	 * suspend/resume callbacks?
+	 */
+	DBG(cdev, "suspend\n");
+	if (cdev->config) {
+		list_for_each_entry(f, &cdev->config->functions, list) {
+			if (f->suspend)
+				f->suspend(f);
+		}
+	}
+}
+
+static void
+composite_resume(struct usb_gadget *gadget)
+{
+	struct usb_composite_dev	*cdev = get_gadget_data(gadget);
+	struct usb_function		*f;
+
+	/* REVISIT:  should we have config and device level
+	 * suspend/resume callbacks?
+	 */
+	DBG(cdev, "resume\n");
+	if (cdev->config) {
+		list_for_each_entry(f, &cdev->config->functions, list) {
+			if (f->resume)
+				f->resume(f);
+		}
+	}
+}
+
+/*-------------------------------------------------------------------------*/
+
+static struct usb_gadget_driver composite_driver = {
+	.speed		= USB_SPEED_HIGH,
+
+	.bind		= composite_bind,
+	.unbind		= __exit_p(composite_unbind),
+
+	.setup		= composite_setup,
+	.disconnect	= composite_disconnect,
+
+	.suspend	= composite_suspend,
+	.resume		= composite_resume,
+
+	.driver	= {
+		.owner		= THIS_MODULE,
+	},
+};
+
+/**
+ * usb_composite_register() - register a composite driver
+ * @driver: the driver to register
+ * Context: single threaded during gadget setup
+ *
+ * This function is used to register drivers using the composite driver
+ * framework.  The return value is zero, or a negative errno value.
+ * Those values normally come from the driver's @bind method, which does
+ * all the work of setting up the driver to match the hardware.
+ *
+ * On successful return, the gadget is ready to respond to requests from
+ * the host, unless one of its components invokes usb_gadget_disconnect()
+ * while it was binding.  That would usually be done in order to wait for
+ * some userspace participation.
+ */
+int __init usb_composite_register(struct usb_composite_driver *driver)
+{
+	if (!driver || !driver->dev || !driver->bind || composite)
+		return -EINVAL;
+
+	if (!driver->name)
+		driver->name = "composite";
+	composite_driver.function =  (char *) driver->name;
+	composite_driver.driver.name = driver->name;
+	composite = driver;
+
+	return usb_gadget_register_driver(&composite_driver);
+}
+
+/**
+ * usb_composite_unregister() - unregister a composite driver
+ * @driver: the driver to unregister
+ *
+ * This function is used to unregister drivers using the composite
+ * driver framework.
+ */
+void __exit usb_composite_unregister(struct usb_composite_driver *driver)
+{
+	if (composite != driver)
+		return;
+	usb_gadget_unregister_driver(&composite_driver);
+}