#include <linux/configfs.h>
  #include <linux/module.h>
  #include <linux/slab.h>
  #include <linux/device.h>
  #include <linux/usb/composite.h>
  #include <linux/usb/gadget_configfs.h>
  #include "configfs.h"
  
  int check_user_usb_string(const char *name,
  		struct usb_gadget_strings *stringtab_dev)
  {
  	unsigned primary_lang;
  	unsigned sub_lang;
  	u16 num;
  	int ret;
  
  	ret = kstrtou16(name, 0, &num);
  	if (ret)
  		return ret;
  
  	primary_lang = num & 0x3ff;
  	sub_lang = num >> 10;
  
  	/* simple sanity check for valid langid */
  	switch (primary_lang) {
  	case 0:
  	case 0x62 ... 0xfe:
  	case 0x100 ... 0x3ff:
  		return -EINVAL;
  	}
  	if (!sub_lang)
  		return -EINVAL;
  
  	stringtab_dev->language = num;
  	return 0;
  }
  
  #define MAX_NAME_LEN	40
  #define MAX_USB_STRING_LANGS 2
  
  struct gadget_info {
  	struct config_group group;
  	struct config_group functions_group;
  	struct config_group configs_group;
  	struct config_group strings_group;
  	struct config_group *default_groups[4];
  
  	struct mutex lock;
  	struct usb_gadget_strings *gstrings[MAX_USB_STRING_LANGS + 1];
  	struct list_head string_list;
  	struct list_head available_func;
  
  	const char *udc_name;
  #ifdef CONFIG_USB_OTG
  	struct usb_otg_descriptor otg;
  #endif
  	struct usb_composite_driver composite;
  	struct usb_composite_dev cdev;
  };
  
  struct config_usb_cfg {
  	struct config_group group;
  	struct config_group strings_group;
  	struct config_group *default_groups[2];
  	struct list_head string_list;
  	struct usb_configuration c;
  	struct list_head func_list;
  	struct usb_gadget_strings *gstrings[MAX_USB_STRING_LANGS + 1];
  };
  
  struct gadget_strings {
  	struct usb_gadget_strings stringtab_dev;
  	struct usb_string strings[USB_GADGET_FIRST_AVAIL_IDX];
  	char *manufacturer;
  	char *product;
  	char *serialnumber;
  
  	struct config_group group;
  	struct list_head list;
  };
  
  struct gadget_config_name {
  	struct usb_gadget_strings stringtab_dev;
  	struct usb_string strings;
  	char *configuration;
  
  	struct config_group group;
  	struct list_head list;
  };
  
  static int usb_string_copy(const char *s, char **s_copy)
  {
  	int ret;
  	char *str;
  	char *copy = *s_copy;
  	ret = strlen(s);
  	if (ret > 126)
  		return -EOVERFLOW;
  
  	str = kstrdup(s, GFP_KERNEL);
  	if (!str)
  		return -ENOMEM;
  	if (str[ret - 1] == '
  ')
  		str[ret - 1] = '\0';
  	kfree(copy);
  	*s_copy = str;
  	return 0;
  }
  
  CONFIGFS_ATTR_STRUCT(gadget_info);
  CONFIGFS_ATTR_STRUCT(config_usb_cfg);
  
  #define GI_DEVICE_DESC_ITEM_ATTR(name)	\
  	static struct gadget_info_attribute gadget_cdev_desc_##name = \
  		__CONFIGFS_ATTR(name,  S_IRUGO | S_IWUSR,		\
  				gadget_dev_desc_##name##_show,		\
  				gadget_dev_desc_##name##_store)
  
  #define GI_DEVICE_DESC_SIMPLE_R_u8(__name)	\
  	static ssize_t gadget_dev_desc_##__name##_show(struct gadget_info *gi, \
  			char *page)	\
  {	\
  	return sprintf(page, "0x%02x
  ", gi->cdev.desc.__name);	\
  }
  
  #define GI_DEVICE_DESC_SIMPLE_R_u16(__name)	\
  	static ssize_t gadget_dev_desc_##__name##_show(struct gadget_info *gi, \
  			char *page)	\
  {	\
  	return sprintf(page, "0x%04x
  ", le16_to_cpup(&gi->cdev.desc.__name)); \
  }
  
  
  #define GI_DEVICE_DESC_SIMPLE_W_u8(_name)		\
  	static ssize_t gadget_dev_desc_##_name##_store(struct gadget_info *gi, \
  		const char *page, size_t len)		\
  {							\
  	u8 val;						\
  	int ret;					\
  	ret = kstrtou8(page, 0, &val);			\
  	if (ret)					\
  		return ret;				\
  	gi->cdev.desc._name = val;			\
  	return len;					\
  }
  
  #define GI_DEVICE_DESC_SIMPLE_W_u16(_name)	\
  	static ssize_t gadget_dev_desc_##_name##_store(struct gadget_info *gi, \
  		const char *page, size_t len)		\
  {							\
  	u16 val;					\
  	int ret;					\
  	ret = kstrtou16(page, 0, &val);			\
  	if (ret)					\
  		return ret;				\
  	gi->cdev.desc._name = cpu_to_le16p(&val);	\
  	return len;					\
  }
  
  #define GI_DEVICE_DESC_SIMPLE_RW(_name, _type)	\
  	GI_DEVICE_DESC_SIMPLE_R_##_type(_name)	\
  	GI_DEVICE_DESC_SIMPLE_W_##_type(_name)
  
  GI_DEVICE_DESC_SIMPLE_R_u16(bcdUSB);
  GI_DEVICE_DESC_SIMPLE_RW(bDeviceClass, u8);
  GI_DEVICE_DESC_SIMPLE_RW(bDeviceSubClass, u8);
  GI_DEVICE_DESC_SIMPLE_RW(bDeviceProtocol, u8);
  GI_DEVICE_DESC_SIMPLE_RW(bMaxPacketSize0, u8);
  GI_DEVICE_DESC_SIMPLE_RW(idVendor, u16);
  GI_DEVICE_DESC_SIMPLE_RW(idProduct, u16);
  GI_DEVICE_DESC_SIMPLE_R_u16(bcdDevice);
  
  static ssize_t is_valid_bcd(u16 bcd_val)
  {
  	if ((bcd_val & 0xf) > 9)
  		return -EINVAL;
  	if (((bcd_val >> 4) & 0xf) > 9)
  		return -EINVAL;
  	if (((bcd_val >> 8) & 0xf) > 9)
  		return -EINVAL;
  	if (((bcd_val >> 12) & 0xf) > 9)
  		return -EINVAL;
  	return 0;
  }
  
  static ssize_t gadget_dev_desc_bcdDevice_store(struct gadget_info *gi,
  		const char *page, size_t len)
  {
  	u16 bcdDevice;
  	int ret;
  
  	ret = kstrtou16(page, 0, &bcdDevice);
  	if (ret)
  		return ret;
  	ret = is_valid_bcd(bcdDevice);
  	if (ret)
  		return ret;
  
  	gi->cdev.desc.bcdDevice = cpu_to_le16(bcdDevice);
  	return len;
  }
  
  static ssize_t gadget_dev_desc_bcdUSB_store(struct gadget_info *gi,
  		const char *page, size_t len)
  {
  	u16 bcdUSB;
  	int ret;
  
  	ret = kstrtou16(page, 0, &bcdUSB);
  	if (ret)
  		return ret;
  	ret = is_valid_bcd(bcdUSB);
  	if (ret)
  		return ret;
  
  	gi->cdev.desc.bcdUSB = cpu_to_le16(bcdUSB);
  	return len;
  }
  
  static ssize_t gadget_dev_desc_UDC_show(struct gadget_info *gi, char *page)
  {
  	return sprintf(page, "%s
  ", gi->udc_name ?: "");
  }
  
  static int unregister_gadget(struct gadget_info *gi)
  {
  	int ret;
  
  	if (!gi->udc_name)
  		return -ENODEV;
  
  	ret = usb_gadget_unregister_driver(&gi->composite.gadget_driver);
  	if (ret)
  		return ret;
  	kfree(gi->udc_name);
  	gi->udc_name = NULL;
  	return 0;
  }
  
  static ssize_t gadget_dev_desc_UDC_store(struct gadget_info *gi,
  		const char *page, size_t len)
  {
  	char *name;
  	int ret;
  
  	name = kstrdup(page, GFP_KERNEL);
  	if (!name)
  		return -ENOMEM;
  	if (name[len - 1] == '
  ')
  		name[len - 1] = '\0';
  
  	mutex_lock(&gi->lock);
  
  	if (!strlen(name)) {
  		ret = unregister_gadget(gi);
  		if (ret)
  			goto err;
  	} else {
  		if (gi->udc_name) {
  			ret = -EBUSY;
  			goto err;
  		}
  		ret = udc_attach_driver(name, &gi->composite.gadget_driver);
  		if (ret)
  			goto err;
  		gi->udc_name = name;
  	}
  	mutex_unlock(&gi->lock);
  	return len;
  err:
  	kfree(name);
  	mutex_unlock(&gi->lock);
  	return ret;
  }
  
  GI_DEVICE_DESC_ITEM_ATTR(bDeviceClass);
  GI_DEVICE_DESC_ITEM_ATTR(bDeviceSubClass);
  GI_DEVICE_DESC_ITEM_ATTR(bDeviceProtocol);
  GI_DEVICE_DESC_ITEM_ATTR(bMaxPacketSize0);
  GI_DEVICE_DESC_ITEM_ATTR(idVendor);
  GI_DEVICE_DESC_ITEM_ATTR(idProduct);
  GI_DEVICE_DESC_ITEM_ATTR(bcdDevice);
  GI_DEVICE_DESC_ITEM_ATTR(bcdUSB);
  GI_DEVICE_DESC_ITEM_ATTR(UDC);
  
  static struct configfs_attribute *gadget_root_attrs[] = {
  	&gadget_cdev_desc_bDeviceClass.attr,
  	&gadget_cdev_desc_bDeviceSubClass.attr,
  	&gadget_cdev_desc_bDeviceProtocol.attr,
  	&gadget_cdev_desc_bMaxPacketSize0.attr,
  	&gadget_cdev_desc_idVendor.attr,
  	&gadget_cdev_desc_idProduct.attr,
  	&gadget_cdev_desc_bcdDevice.attr,
  	&gadget_cdev_desc_bcdUSB.attr,
  	&gadget_cdev_desc_UDC.attr,
  	NULL,
  };
  
  static inline struct gadget_info *to_gadget_info(struct config_item *item)
  {
  	 return container_of(to_config_group(item), struct gadget_info, group);
  }
  
  static inline struct gadget_strings *to_gadget_strings(struct config_item *item)
  {
  	 return container_of(to_config_group(item), struct gadget_strings,
  			 group);
  }
  
  static inline struct gadget_config_name *to_gadget_config_name(
  		struct config_item *item)
  {
  	 return container_of(to_config_group(item), struct gadget_config_name,
  			 group);
  }
  
  static inline struct config_usb_cfg *to_config_usb_cfg(struct config_item *item)
  {
  	return container_of(to_config_group(item), struct config_usb_cfg,
  			group);
  }
  
  static inline struct usb_function_instance *to_usb_function_instance(
  		struct config_item *item)
  {
  	 return container_of(to_config_group(item),
  			 struct usb_function_instance, group);
  }
  
  static void gadget_info_attr_release(struct config_item *item)
  {
  	struct gadget_info *gi = to_gadget_info(item);
  
  	WARN_ON(!list_empty(&gi->cdev.configs));
  	WARN_ON(!list_empty(&gi->string_list));
  	WARN_ON(!list_empty(&gi->available_func));
  	kfree(gi->composite.gadget_driver.function);
  	kfree(gi);
  }
  
  CONFIGFS_ATTR_OPS(gadget_info);
  
  static struct configfs_item_operations gadget_root_item_ops = {
  	.release                = gadget_info_attr_release,
  	.show_attribute         = gadget_info_attr_show,
  	.store_attribute        = gadget_info_attr_store,
  };
  
  static void gadget_config_attr_release(struct config_item *item)
  {
  	struct config_usb_cfg *cfg = to_config_usb_cfg(item);
  
  	WARN_ON(!list_empty(&cfg->c.functions));
  	list_del(&cfg->c.list);
  	kfree(cfg->c.label);
  	kfree(cfg);
  }
  
  static int config_usb_cfg_link(
  	struct config_item *usb_cfg_ci,
  	struct config_item *usb_func_ci)
  {
  	struct config_usb_cfg *cfg = to_config_usb_cfg(usb_cfg_ci);
  	struct usb_composite_dev *cdev = cfg->c.cdev;
  	struct gadget_info *gi = container_of(cdev, struct gadget_info, cdev);
  
  	struct config_group *group = to_config_group(usb_func_ci);
  	struct usb_function_instance *fi = container_of(group,
  			struct usb_function_instance, group);
  	struct usb_function_instance *a_fi;
  	struct usb_function *f;
  	int ret;
  
  	mutex_lock(&gi->lock);
  	/*
  	 * Make sure this function is from within our _this_ gadget and not
  	 * from another gadget or a random directory.
  	 * Also a function instance can only be linked once.
  	 */
  	list_for_each_entry(a_fi, &gi->available_func, cfs_list) {
  		if (a_fi == fi)
  			break;
  	}
  	if (a_fi != fi) {
  		ret = -EINVAL;
  		goto out;
  	}
  
  	list_for_each_entry(f, &cfg->func_list, list) {
  		if (f->fi == fi) {
  			ret = -EEXIST;
  			goto out;
  		}
  	}
  
  	f = usb_get_function(fi);
  	if (IS_ERR(f)) {
  		ret = PTR_ERR(f);
  		goto out;
  	}
  
  	/* stash the function until we bind it to the gadget */
  	list_add_tail(&f->list, &cfg->func_list);
  	ret = 0;
  out:
  	mutex_unlock(&gi->lock);
  	return ret;
  }
  
  static int config_usb_cfg_unlink(
  	struct config_item *usb_cfg_ci,
  	struct config_item *usb_func_ci)
  {
  	struct config_usb_cfg *cfg = to_config_usb_cfg(usb_cfg_ci);
  	struct usb_composite_dev *cdev = cfg->c.cdev;
  	struct gadget_info *gi = container_of(cdev, struct gadget_info, cdev);
  
  	struct config_group *group = to_config_group(usb_func_ci);
  	struct usb_function_instance *fi = container_of(group,
  			struct usb_function_instance, group);
  	struct usb_function *f;
  
  	/*
  	 * ideally I would like to forbid to unlink functions while a gadget is
  	 * bound to an UDC. Since this isn't possible at the moment, we simply
  	 * force an unbind, the function is available here and then we can
  	 * remove the function.
  	 */
  	mutex_lock(&gi->lock);
  	if (gi->udc_name)
  		unregister_gadget(gi);
  	WARN_ON(gi->udc_name);
  
  	list_for_each_entry(f, &cfg->func_list, list) {
  		if (f->fi == fi) {
  			list_del(&f->list);
  			usb_put_function(f);
  			mutex_unlock(&gi->lock);
  			return 0;
  		}
  	}
  	mutex_unlock(&gi->lock);
  	WARN(1, "Unable to locate function to unbind
  ");
  	return 0;
  }
  
  CONFIGFS_ATTR_OPS(config_usb_cfg);
  
  static struct configfs_item_operations gadget_config_item_ops = {
  	.release                = gadget_config_attr_release,
  	.show_attribute         = config_usb_cfg_attr_show,
  	.store_attribute        = config_usb_cfg_attr_store,
  	.allow_link             = config_usb_cfg_link,
  	.drop_link              = config_usb_cfg_unlink,
  };
  
  
  static ssize_t gadget_config_desc_MaxPower_show(struct config_usb_cfg *cfg,
  		char *page)
  {
  	return sprintf(page, "%u
  ", cfg->c.MaxPower);
  }
  
  static ssize_t gadget_config_desc_MaxPower_store(struct config_usb_cfg *cfg,
  		const char *page, size_t len)
  {
  	u16 val;
  	int ret;
  	ret = kstrtou16(page, 0, &val);
  	if (ret)
  		return ret;
  	if (DIV_ROUND_UP(val, 8) > 0xff)
  		return -ERANGE;
  	cfg->c.MaxPower = val;
  	return len;
  }
  
  static ssize_t gadget_config_desc_bmAttributes_show(struct config_usb_cfg *cfg,
  		char *page)
  {
  	return sprintf(page, "0x%02x
  ", cfg->c.bmAttributes);
  }
  
  static ssize_t gadget_config_desc_bmAttributes_store(struct config_usb_cfg *cfg,
  		const char *page, size_t len)
  {
  	u8 val;
  	int ret;
  	ret = kstrtou8(page, 0, &val);
  	if (ret)
  		return ret;
  	if (!(val & USB_CONFIG_ATT_ONE))
  		return -EINVAL;
  	if (val & ~(USB_CONFIG_ATT_ONE | USB_CONFIG_ATT_SELFPOWER |
  				USB_CONFIG_ATT_WAKEUP))
  		return -EINVAL;
  	cfg->c.bmAttributes = val;
  	return len;
  }
  
  #define CFG_CONFIG_DESC_ITEM_ATTR(name)	\
  	static struct config_usb_cfg_attribute gadget_usb_cfg_##name = \
  		__CONFIGFS_ATTR(name,  S_IRUGO | S_IWUSR,		\
  				gadget_config_desc_##name##_show,	\
  				gadget_config_desc_##name##_store)
  
  CFG_CONFIG_DESC_ITEM_ATTR(MaxPower);
  CFG_CONFIG_DESC_ITEM_ATTR(bmAttributes);
  
  static struct configfs_attribute *gadget_config_attrs[] = {
  	&gadget_usb_cfg_MaxPower.attr,
  	&gadget_usb_cfg_bmAttributes.attr,
  	NULL,
  };
  
  static struct config_item_type gadget_config_type = {
  	.ct_item_ops	= &gadget_config_item_ops,
  	.ct_attrs	= gadget_config_attrs,
  	.ct_owner	= THIS_MODULE,
  };
  
  static struct config_item_type gadget_root_type = {
  	.ct_item_ops	= &gadget_root_item_ops,
  	.ct_attrs	= gadget_root_attrs,
  	.ct_owner	= THIS_MODULE,
  };
  
  static void composite_init_dev(struct usb_composite_dev *cdev)
  {
  	spin_lock_init(&cdev->lock);
  	INIT_LIST_HEAD(&cdev->configs);
  	INIT_LIST_HEAD(&cdev->gstrings);
  }
  
  static struct config_group *function_make(
  		struct config_group *group,
  		const char *name)
  {
  	struct gadget_info *gi;
  	struct usb_function_instance *fi;
  	char buf[MAX_NAME_LEN];
  	char *func_name;
  	char *instance_name;
  	int ret;
  
  	ret = snprintf(buf, MAX_NAME_LEN, "%s", name);
  	if (ret >= MAX_NAME_LEN)
  		return ERR_PTR(-ENAMETOOLONG);
  
  	func_name = buf;
  	instance_name = strchr(func_name, '.');
  	if (!instance_name) {
  		pr_err("Unable to locate . in FUNC.INSTANCE
  ");
  		return ERR_PTR(-EINVAL);
  	}
  	*instance_name = '\0';
  	instance_name++;
  
  	fi = usb_get_function_instance(func_name);
  	if (IS_ERR(fi))
  		return ERR_CAST(fi);
  
  	ret = config_item_set_name(&fi->group.cg_item, name);
  	if (ret) {
  		usb_put_function_instance(fi);
  		return ERR_PTR(ret);
  	}
  	if (fi->set_inst_name) {
  		ret = fi->set_inst_name(fi, instance_name);
  		if (ret) {
  			usb_put_function_instance(fi);
  			return ERR_PTR(ret);
  		}
  	}
  
  	gi = container_of(group, struct gadget_info, functions_group);
  
  	mutex_lock(&gi->lock);
  	list_add_tail(&fi->cfs_list, &gi->available_func);
  	mutex_unlock(&gi->lock);
  	return &fi->group;
  }
  
  static void function_drop(
  		struct config_group *group,
  		struct config_item *item)
  {
  	struct usb_function_instance *fi = to_usb_function_instance(item);
  	struct gadget_info *gi;
  
  	gi = container_of(group, struct gadget_info, functions_group);
  
  	mutex_lock(&gi->lock);
  	list_del(&fi->cfs_list);
  	mutex_unlock(&gi->lock);
  	config_item_put(item);
  }
  
  static struct configfs_group_operations functions_ops = {
  	.make_group     = &function_make,
  	.drop_item      = &function_drop,
  };
  
  static struct config_item_type functions_type = {
  	.ct_group_ops   = &functions_ops,
  	.ct_owner       = THIS_MODULE,
  };
  
  CONFIGFS_ATTR_STRUCT(gadget_config_name);
  GS_STRINGS_RW(gadget_config_name, configuration);
  
  static struct configfs_attribute *gadget_config_name_langid_attrs[] = {
  	&gadget_config_name_configuration.attr,
  	NULL,
  };
  
  static void gadget_config_name_attr_release(struct config_item *item)
  {
  	struct gadget_config_name *cn = to_gadget_config_name(item);
  
  	kfree(cn->configuration);
  
  	list_del(&cn->list);
  	kfree(cn);
  }
  
  USB_CONFIG_STRING_RW_OPS(gadget_config_name);
  USB_CONFIG_STRINGS_LANG(gadget_config_name, config_usb_cfg);
  
  static struct config_group *config_desc_make(
  		struct config_group *group,
  		const char *name)
  {
  	struct gadget_info *gi;
  	struct config_usb_cfg *cfg;
  	char buf[MAX_NAME_LEN];
  	char *num_str;
  	u8 num;
  	int ret;
  
  	gi = container_of(group, struct gadget_info, configs_group);
  	ret = snprintf(buf, MAX_NAME_LEN, "%s", name);
  	if (ret >= MAX_NAME_LEN)
  		return ERR_PTR(-ENAMETOOLONG);
  
  	num_str = strchr(buf, '.');
  	if (!num_str) {
  		pr_err("Unable to locate . in name.bConfigurationValue
  ");
  		return ERR_PTR(-EINVAL);
  	}
  
  	*num_str = '\0';
  	num_str++;
  
  	if (!strlen(buf))
  		return ERR_PTR(-EINVAL);
  
  	ret = kstrtou8(num_str, 0, &num);
  	if (ret)
  		return ERR_PTR(ret);
  
  	cfg = kzalloc(sizeof(*cfg), GFP_KERNEL);
  	if (!cfg)
  		return ERR_PTR(-ENOMEM);
  	cfg->c.label = kstrdup(buf, GFP_KERNEL);
  	if (!cfg->c.label) {
  		ret = -ENOMEM;
  		goto err;
  	}
  	cfg->c.bConfigurationValue = num;
  	cfg->c.MaxPower = CONFIG_USB_GADGET_VBUS_DRAW;
  	cfg->c.bmAttributes = USB_CONFIG_ATT_ONE;
  	INIT_LIST_HEAD(&cfg->string_list);
  	INIT_LIST_HEAD(&cfg->func_list);
  
  	cfg->group.default_groups = cfg->default_groups;
  	cfg->default_groups[0] = &cfg->strings_group;
  
  	config_group_init_type_name(&cfg->group, name,
  				&gadget_config_type);
  	config_group_init_type_name(&cfg->strings_group, "strings",
  			&gadget_config_name_strings_type);
  
  	ret = usb_add_config_only(&gi->cdev, &cfg->c);
  	if (ret)
  		goto err;
  
  	return &cfg->group;
  err:
  	kfree(cfg->c.label);
  	kfree(cfg);
  	return ERR_PTR(ret);
  }
  
  static void config_desc_drop(
  		struct config_group *group,
  		struct config_item *item)
  {
  	config_item_put(item);
  }
  
  static struct configfs_group_operations config_desc_ops = {
  	.make_group     = &config_desc_make,
  	.drop_item      = &config_desc_drop,
  };
  
  static struct config_item_type config_desc_type = {
  	.ct_group_ops   = &config_desc_ops,
  	.ct_owner       = THIS_MODULE,
  };
  
  CONFIGFS_ATTR_STRUCT(gadget_strings);
  GS_STRINGS_RW(gadget_strings, manufacturer);
  GS_STRINGS_RW(gadget_strings, product);
  GS_STRINGS_RW(gadget_strings, serialnumber);
  
  static struct configfs_attribute *gadget_strings_langid_attrs[] = {
  	&gadget_strings_manufacturer.attr,
  	&gadget_strings_product.attr,
  	&gadget_strings_serialnumber.attr,
  	NULL,
  };
  
  static void gadget_strings_attr_release(struct config_item *item)
  {
  	struct gadget_strings *gs = to_gadget_strings(item);
  
  	kfree(gs->manufacturer);
  	kfree(gs->product);
  	kfree(gs->serialnumber);
  
  	list_del(&gs->list);
  	kfree(gs);
  }
  
  USB_CONFIG_STRING_RW_OPS(gadget_strings);
  USB_CONFIG_STRINGS_LANG(gadget_strings, gadget_info);
  
  static int configfs_do_nothing(struct usb_composite_dev *cdev)
  {
  	WARN_ON(1);
  	return -EINVAL;
  }
  
  int composite_dev_prepare(struct usb_composite_driver *composite,
  		struct usb_composite_dev *dev);
  
  static void purge_configs_funcs(struct gadget_info *gi)
  {
  	struct usb_configuration	*c;
  
  	list_for_each_entry(c, &gi->cdev.configs, list) {
  		struct usb_function *f, *tmp;
  		struct config_usb_cfg *cfg;
  
  		cfg = container_of(c, struct config_usb_cfg, c);
  
  		list_for_each_entry_safe(f, tmp, &c->functions, list) {
  
  			list_move_tail(&f->list, &cfg->func_list);
  			if (f->unbind) {
  				dev_err(&gi->cdev.gadget->dev, "unbind function"
  						" '%s'/%p
  ", f->name, f);
  				f->unbind(c, f);
  			}
  		}
  		c->next_interface_id = 0;
  		c->superspeed = 0;
  		c->highspeed = 0;
  		c->fullspeed = 0;
  	}
  }
  
  static int configfs_composite_bind(struct usb_gadget *gadget,
  		struct usb_gadget_driver *gdriver)
  {
  	struct usb_composite_driver     *composite = to_cdriver(gdriver);
  	struct gadget_info		*gi = container_of(composite,
  						struct gadget_info, composite);
  	struct usb_composite_dev	*cdev = &gi->cdev;
  	struct usb_configuration	*c;
  	struct usb_string		*s;
  	unsigned			i;
  	int				ret;
  
  	/* the gi->lock is hold by the caller */
  	cdev->gadget = gadget;
  	set_gadget_data(gadget, cdev);
  	ret = composite_dev_prepare(composite, cdev);
  	if (ret)
  		return ret;
  	/* and now the gadget bind */
  	ret = -EINVAL;
  
  	if (list_empty(&gi->cdev.configs)) {
  		pr_err("Need at least one configuration in %s.
  ",
  				gi->composite.name);
  		goto err_comp_cleanup;
  	}
  
  
  	list_for_each_entry(c, &gi->cdev.configs, list) {
  		struct config_usb_cfg *cfg;
  
  		cfg = container_of(c, struct config_usb_cfg, c);
  		if (list_empty(&cfg->func_list)) {
  			pr_err("Config %s/%d of %s needs at least one function.
  ",
  			      c->label, c->bConfigurationValue,
  			      gi->composite.name);
  			goto err_comp_cleanup;
  		}
  	}
  
  	/* init all strings */
  	if (!list_empty(&gi->string_list)) {
  		struct gadget_strings *gs;
  
  		i = 0;
  		list_for_each_entry(gs, &gi->string_list, list) {
  
  			gi->gstrings[i] = &gs->stringtab_dev;
  			gs->stringtab_dev.strings = gs->strings;
  			gs->strings[USB_GADGET_MANUFACTURER_IDX].s =
  				gs->manufacturer;
  			gs->strings[USB_GADGET_PRODUCT_IDX].s = gs->product;
  			gs->strings[USB_GADGET_SERIAL_IDX].s = gs->serialnumber;
  			i++;
  		}
  		gi->gstrings[i] = NULL;
  		s = usb_gstrings_attach(&gi->cdev, gi->gstrings,
  				USB_GADGET_FIRST_AVAIL_IDX);
  		if (IS_ERR(s)) {
  			ret = PTR_ERR(s);
  			goto err_comp_cleanup;
  		}
  
  		gi->cdev.desc.iManufacturer = s[USB_GADGET_MANUFACTURER_IDX].id;
  		gi->cdev.desc.iProduct = s[USB_GADGET_PRODUCT_IDX].id;
  		gi->cdev.desc.iSerialNumber = s[USB_GADGET_SERIAL_IDX].id;
  	}
  
  	/* Go through all configs, attach all functions */
  	list_for_each_entry(c, &gi->cdev.configs, list) {
  		struct config_usb_cfg *cfg;
  		struct usb_function *f;
  		struct usb_function *tmp;
  		struct gadget_config_name *cn;
  
  		cfg = container_of(c, struct config_usb_cfg, c);
  		if (!list_empty(&cfg->string_list)) {
  			i = 0;
  			list_for_each_entry(cn, &cfg->string_list, list) {
  				cfg->gstrings[i] = &cn->stringtab_dev;
  				cn->stringtab_dev.strings = &cn->strings;
  				cn->strings.s = cn->configuration;
  				i++;
  			}
  			cfg->gstrings[i] = NULL;
  			s = usb_gstrings_attach(&gi->cdev, cfg->gstrings, 1);
  			if (IS_ERR(s)) {
  				ret = PTR_ERR(s);
  				goto err_comp_cleanup;
  			}
  			c->iConfiguration = s[0].id;
  		}
  
  		list_for_each_entry_safe(f, tmp, &cfg->func_list, list) {
  			list_del(&f->list);
  			ret = usb_add_function(c, f);
  			if (ret) {
  				list_add(&f->list, &cfg->func_list);
  				goto err_purge_funcs;
  			}
  		}
  		usb_ep_autoconfig_reset(cdev->gadget);
  	}
  	usb_ep_autoconfig_reset(cdev->gadget);
  	return 0;
  
  err_purge_funcs:
  	purge_configs_funcs(gi);
  err_comp_cleanup:
  	composite_dev_cleanup(cdev);
  	return ret;
  }
  
  static void configfs_composite_unbind(struct usb_gadget *gadget)
  {
  	struct usb_composite_dev	*cdev;
  	struct gadget_info		*gi;
  
  	/* the gi->lock is hold by the caller */
  
  	cdev = get_gadget_data(gadget);
  	gi = container_of(cdev, struct gadget_info, cdev);
  
  	purge_configs_funcs(gi);
  	composite_dev_cleanup(cdev);
  	usb_ep_autoconfig_reset(cdev->gadget);
  	cdev->gadget = NULL;
  	set_gadget_data(gadget, NULL);
  }
  
  static const struct usb_gadget_driver configfs_driver_template = {
  	.bind           = configfs_composite_bind,
  	.unbind         = configfs_composite_unbind,
  
  	.setup          = composite_setup,
  	.disconnect     = composite_disconnect,
  
  	.max_speed	= USB_SPEED_SUPER,
  	.driver = {
  		.owner          = THIS_MODULE,
  		.name		= "configfs-gadget",
  	},
  };
  
  static struct config_group *gadgets_make(
  		struct config_group *group,
  		const char *name)
  {
  	struct gadget_info *gi;
  
  	gi = kzalloc(sizeof(*gi), GFP_KERNEL);
  	if (!gi)
  		return ERR_PTR(-ENOMEM);
  
  	gi->group.default_groups = gi->default_groups;
  	gi->group.default_groups[0] = &gi->functions_group;
  	gi->group.default_groups[1] = &gi->configs_group;
  	gi->group.default_groups[2] = &gi->strings_group;
  
  	config_group_init_type_name(&gi->functions_group, "functions",
  			&functions_type);
  	config_group_init_type_name(&gi->configs_group, "configs",
  			&config_desc_type);
  	config_group_init_type_name(&gi->strings_group, "strings",
  			&gadget_strings_strings_type);
  
  	gi->composite.bind = configfs_do_nothing;
  	gi->composite.unbind = configfs_do_nothing;
  	gi->composite.suspend = NULL;
  	gi->composite.resume = NULL;
  	gi->composite.max_speed = USB_SPEED_SUPER;
  
  	mutex_init(&gi->lock);
  	INIT_LIST_HEAD(&gi->string_list);
  	INIT_LIST_HEAD(&gi->available_func);
  
  	composite_init_dev(&gi->cdev);
  	gi->cdev.desc.bLength = USB_DT_DEVICE_SIZE;
  	gi->cdev.desc.bDescriptorType = USB_DT_DEVICE;
  	gi->cdev.desc.bcdDevice = cpu_to_le16(get_default_bcdDevice());
  
  	gi->composite.gadget_driver = configfs_driver_template;
  
  	gi->composite.gadget_driver.function = kstrdup(name, GFP_KERNEL);
  	gi->composite.name = gi->composite.gadget_driver.function;
  
  	if (!gi->composite.gadget_driver.function)
  		goto err;
  
  #ifdef CONFIG_USB_OTG
  	gi->otg.bLength = sizeof(struct usb_otg_descriptor);
  	gi->otg.bDescriptorType = USB_DT_OTG;
  	gi->otg.bmAttributes = USB_OTG_SRP | USB_OTG_HNP;
  #endif
  
  	config_group_init_type_name(&gi->group, name,
  				&gadget_root_type);
  	return &gi->group;
  err:
  	kfree(gi);
  	return ERR_PTR(-ENOMEM);
  }
  
  static void gadgets_drop(struct config_group *group, struct config_item *item)
  {
  	config_item_put(item);
  }
  
  static struct configfs_group_operations gadgets_ops = {
  	.make_group     = &gadgets_make,
  	.drop_item      = &gadgets_drop,
  };
  
  static struct config_item_type gadgets_type = {
  	.ct_group_ops   = &gadgets_ops,
  	.ct_owner       = THIS_MODULE,
  };
  
  static struct configfs_subsystem gadget_subsys = {
  	.su_group = {
  		.cg_item = {
  			.ci_namebuf = "usb_gadget",
  			.ci_type = &gadgets_type,
  		},
  	},
  	.su_mutex = __MUTEX_INITIALIZER(gadget_subsys.su_mutex),
  };
  
  void unregister_gadget_item(struct config_item *item)
  {
  	struct gadget_info *gi = to_gadget_info(item);
  
  	unregister_gadget(gi);
  }
  EXPORT_SYMBOL(unregister_gadget_item);
  
  static int __init gadget_cfs_init(void)
  {
  	int ret;
  
  	config_group_init(&gadget_subsys.su_group);
  
  	ret = configfs_register_subsystem(&gadget_subsys);
  	return ret;
  }
  module_init(gadget_cfs_init);
  
  static void __exit gadget_cfs_exit(void)
  {
  	configfs_unregister_subsystem(&gadget_subsys);
  }
  module_exit(gadget_cfs_exit);