usb: gadget: the start of the configfs interface

|# modprobe dummy_hcd num=2
|# modprobe libcomposite

|# lsmod
|Module                  Size  Used by
|libcomposite           31648  0
|dummy_hcd              19871  0

|# mkdir /sys/kernel/config/usb_gadget/oha
|# cd /sys/kernel/config/usb_gadget/oha
|# mkdir configs/def.1
|# mkdir configs/def.2
|# mkdir functions/acm.ttyS1
|# mkdir strings/0x1
|mkdir: cannot create directory `strings/0x1': Invalid argument
|# mkdir strings/0x409
|# mkdir strings/1033
|mkdir: cannot create directory `strings/1033': File exists
|# mkdir strings/1032
|# mkdir configs/def.1/strings/0x409
|# mkdir configs/def.2/strings/0x409

|#find . -ls
|   975    0 drwxr-xr-x   5 root     root            0 Dec 23 17:40 .
|   978    0 drwxr-xr-x   4 root     root            0 Dec 23 17:43 ./strings
|  4100    0 drwxr-xr-x   2 root     root            0 Dec 23 17:43 ./strings/1032
|   995    0 -rw-r--r--   1 root     root         4096 Dec 23 17:43 ./strings/1032/serialnumber
|   996    0 -rw-r--r--   1 root     root         4096 Dec 23 17:43 ./strings/1032/product
|   997    0 -rw-r--r--   1 root     root         4096 Dec 23 17:43 ./strings/1032/manufacturer
|  2002    0 drwxr-xr-x   2 root     root            0 Dec 23 17:41 ./strings/0x409
|   998    0 -rw-r--r--   1 root     root         4096 Dec 23 17:43 ./strings/0x409/serialnumber
|   999    0 -rw-r--r--   1 root     root         4096 Dec 23 17:43 ./strings/0x409/product
|  1000    0 -rw-r--r--   1 root     root         4096 Dec 23 17:43 ./strings/0x409/manufacturer
|   977    0 drwxr-xr-x   4 root     root            0 Dec 23 17:41 ./configs
|  4081    0 drwxr-xr-x   3 root     root            0 Dec 23 17:41 ./configs/def.2
|  4082    0 drwxr-xr-x   3 root     root            0 Dec 23 17:42 ./configs/def.2/strings
|  2016    0 drwxr-xr-x   2 root     root            0 Dec 23 17:42 ./configs/def.2/strings/0x409
|  1001    0 -rw-r--r--   1 root     root         4096 Dec 23 17:43 ./configs/def.2/strings/0x409/configuration
|  1002    0 -rw-r--r--   1 root     root         4096 Dec 23 17:43 ./configs/def.2/bmAttributes
|  1003    0 -rw-r--r--   1 root     root         4096 Dec 23 17:43 ./configs/def.2/MaxPower
|   979    0 drwxr-xr-x   3 root     root            0 Dec 23 17:42 ./configs/def.1
|   980    0 drwxr-xr-x   3 root     root            0 Dec 23 17:42 ./configs/def.1/strings
|  5122    0 drwxr-xr-x   2 root     root            0 Dec 23 17:42 ./configs/def.1/strings/0x409
|  1004    0 -rw-r--r--   1 root     root         4096 Dec 23 17:43 ./configs/def.1/strings/0x409/configuration
|  1005    0 -rw-r--r--   1 root     root         4096 Dec 23 17:43 ./configs/def.1/bmAttributes
|  1006    0 -rw-r--r--   1 root     root         4096 Dec 23 17:43 ./configs/def.1/MaxPower
|   976    0 drwxr-xr-x   3 root     root            0 Dec 23 17:41 ./functions
|   981    0 drwxr-xr-x   2 root     root            0 Dec 23 17:41 ./functions/acm.ttyS1
|  1007    0 -r--r--r--   1 root     root         4096 Dec 23 17:43 ./functions/acm.ttyS1/port_num
|  1008    0 -rw-r--r--   1 root     root         4096 Dec 23 17:43 ./UDC
|  1009    0 -rw-r--r--   1 root     root         4096 Dec 23 17:43 ./bcdUSB
|  1010    0 -rw-r--r--   1 root     root         4096 Dec 23 17:43 ./bcdDevice
|  1011    0 -rw-r--r--   1 root     root         4096 Dec 23 17:43 ./idProduct
|  1012    0 -rw-r--r--   1 root     root         4096 Dec 23 17:43 ./idVendor
|  1013    0 -rw-r--r--   1 root     root         4096 Dec 23 17:43 ./bMaxPacketSize0
|  1014    0 -rw-r--r--   1 root     root         4096 Dec 23 17:43 ./bDeviceProtocol
|  1015    0 -rw-r--r--   1 root     root         4096 Dec 23 17:43 ./bDeviceSubClass
|  1016    0 -rw-r--r--   1 root     root         4096 Dec 23 17:43 ./bDeviceClass

|# cat functions/acm.ttyS1/port_num
|0
|# ls -lah /dev/ttyGS*
|crw-rw---T 1 root dialout 252, 0 Dec 23 17:41 /dev/ttyGS0
|
|# echo 0x1234 > idProduct
|# echo 0xabcd > idVendor
|# echo 1122 > strings/0x409/serialnumber
|# echo "The manufacturer" > strings/0x409/manufacturer
|# echo 1 > strings/1032/manufacturer
|# echo 1sa > strings/1032/product
|# echo tada > strings/1032/serialnumber
|echo "Primary configuration" > configs/def.1/strings/0x409/configuration
|# echo "Secondary configuration" > configs/def.2/strings/0x409/configuration
|# ln -s functions/acm.ttyS1 configs/def.1/
|# ln -s functions/acm.ttyS1 configs/def.2/
|find configs/def.1/ -ls
|   979    0 drwxr-xr-x   3 root     root            0 Dec 23 17:49 configs/def.1/
|  6264    0 lrwxrwxrwx   1 root     root            0 Dec 23 17:48 configs/def.1/acm.ttyS1 -> ../../../../usb_gadget/oha/functions/acm.ttyS1
|   980    0 drwxr-xr-x   3 root     root            0 Dec 23 17:42 configs/def.1/strings
|  5122    0 drwxr-xr-x   2 root     root            0 Dec 23 17:49 configs/def.1/strings/0x409
|  6284    0 -rw-r--r--   1 root     root         4096 Dec 23 17:47 configs/def.1/strings/0x409/configuration
|  6285    0 -rw-r--r--   1 root     root         4096 Dec 23 17:49 configs/def.1/bmAttributes
|  6286    0 -rw-r--r--   1 root     root         4096 Dec 23 17:49 configs/def.1/MaxPower
|
|echo 120 > configs/def.1/MaxPower
|
|# ls -lh /sys/class/udc/
|total 0
|lrwxrwxrwx 1 root root 0 Dec 23 17:50 dummy_udc.0 -> ../../devices/platform/dummy_udc.0/udc/dummy_udc.0
|lrwxrwxrwx 1 root root 0 Dec 23 17:50 dummy_udc.1 -> ../../devices/platform/dummy_udc.1/udc/dummy_udc.1
|# echo dummy_udc.0 > UDC
|# lsusb
|Bus 001 Device 002: ID abcd:1234 Unknown
|
|lsusb -d abcd:1234 -v
|Device Descriptor:
…
|  idVendor           0xabcd Unknown
|  idProduct          0x1234
|  bcdDevice            3.06
|  iManufacturer           1 The manufacturer
|  iProduct                2
|  iSerial                 3 1122
|  bNumConfigurations      2
…
|echo "" > UDC

v5…v6
- wired up strings with usb_gstrings_attach()
- add UDC attribe. Write "udc-name" will bind the gadget. Write an empty
  string (it should contain \n since 0 bytes write get optimzed away)
  will unbind the UDC from the gadget. The name of available UDCs can be
  obtained from /sys/class/udc/

v4…v5
- string rework. This will add a strings folder incl. language code like
    strings/409/manufacturer
  as suggested by Alan.
- rebased ontop reworked functions.c which has usb_function_instance
  which is used prior after "mkdir acm.instance" and can be directly
  used for configuration via configfs.

v3…v4
 - moved functions from the root folde down to the gadget as suggested
   by Michał
 - configs have now their own configs folder as suggested by Michał.
   The folder is still name.bConfigurationValue where name becomes the
   sConfiguration. Is this usefull should we just stilc
   configs/bConfigurationValue/ ?
 - added configfs support to the ACM function. The port_num attribute is
   exported by f_acm. An argument has been added to the USB alloc
   function to distinguish between "old" (use facm_configure() to
   configure and configfs interface (expose a config_node).
   The port_num is currently a dumb counter. It will
   require some function re-work to make it work.

scheduled for v5:
- sym linking function into config.

v2…v3
- replaced one ifndef by ifdef as suggested by Micahał
- strstr()/strchr() function_make as suggested by Micahł
- replace [iSerialNumber|iProduct|iManufacturer] with
  [sSerialNumber|sProduct|sManufacturer] as suggested by Alan
- added creation of config descriptors

v1…v2
- moved gadgets from configfs' root directory into /udcs/ within our
  "usb_gadget" folder. Requested by Andrzej & Michał
- use a dot as a delimiter between function's name and its instance's name
  as suggested by Michał
- renamed all config_item_type, configfs_group_operations, make_group,
  drop_item as suggested by suggested by Andrzej to remain consisten
  within this file and within other configfs users
- Since configfs.c and functions.c are now part of the udc-core module,
  the module itself is now called udc. Also added a tiny ifdef around
  init code becuase udc-core is subsys init and this is too early for
  configfs in the built-in case. In the module case, we can only have
  one init function.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/gadget/Kconfig

@@ -493,6 +493,7 @@ endmenu
 # composite based drivers
 config USB_LIBCOMPOSITE
 	tristate
+	select CONFIGFS_FS
 	depends on USB_GADGET
 
 config USB_F_ACM

drivers/usb/gadget/Makefile

@@ -6,7 +6,7 @@ ccflags-$(CONFIG_USB_GADGET_DEBUG) := -DDEBUG
 obj-$(CONFIG_USB_GADGET)	+= udc-core.o
 obj-$(CONFIG_USB_LIBCOMPOSITE)	+= libcomposite.o
 libcomposite-y			:= usbstring.o config.o epautoconf.o
-libcomposite-y			+= composite.o functions.o
+libcomposite-y			+= composite.o functions.o configfs.o
 obj-$(CONFIG_USB_DUMMY_HCD)	+= dummy_hcd.o
 obj-$(CONFIG_USB_NET2272)	+= net2272.o
 obj-$(CONFIG_USB_NET2280)	+= net2280.o

drivers/usb/gadget/composite.c

@@ -1637,6 +1637,7 @@ void composite_dev_cleanup(struct usb_composite_dev *cdev)
 		kfree(cdev->req->buf);
 		usb_ep_free_request(cdev->gadget->ep0, cdev->req);
 	}
+	cdev->next_string_id = 0;
 	device_remove_file(&cdev->gadget->dev, &dev_attr_suspended);
 }
 

drivers/usb/gadget/configfs.c

+#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>
+
+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] == '\n')
+		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\n", 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\n", 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\n", 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] == '\n')
+		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_printf("Unable to locate function to unbind\n");
+	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\n", 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\n", 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\n");
+		return ERR_PTR(-EINVAL);
+	}
+	*instance_name = '\0';
+	instance_name++;
+
+	fi = usb_get_function_instance(func_name);
+	if (IS_ERR(fi))
+		return ERR_PTR(PTR_ERR(fi));
+
+	ret = config_item_set_name(&fi->group.cg_item, 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\n");
+		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();
+	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\n", 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 atleast one configuration in %s.\n",
+				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 atleast one function.\n",
+			      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))
+			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))
+				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)
+				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),
+};
+
+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);

drivers/usb/gadget/f_acm.c

@@ -763,6 +763,59 @@ static struct usb_function *acm_alloc_func(struct usb_function_instance *fi)
 	return &acm->port.func;
 }
 
+static inline struct f_serial_opts *to_f_serial_opts(struct config_item *item)
+{
+	return container_of(to_config_group(item), struct f_serial_opts,
+			func_inst.group);
+}
+
+CONFIGFS_ATTR_STRUCT(f_serial_opts);
+static ssize_t f_acm_attr_show(struct config_item *item,
+				 struct configfs_attribute *attr,
+				 char *page)
+{
+	struct f_serial_opts *opts = to_f_serial_opts(item);
+	struct f_serial_opts_attribute *f_serial_opts_attr =
+		container_of(attr, struct f_serial_opts_attribute, attr);
+	ssize_t ret = 0;
+
+	if (f_serial_opts_attr->show)
+		ret = f_serial_opts_attr->show(opts, page);
+	return ret;
+}
+
+static void acm_attr_release(struct config_item *item)
+{
+	struct f_serial_opts *opts = to_f_serial_opts(item);
+
+	usb_put_function_instance(&opts->func_inst);
+}
+
+static struct configfs_item_operations acm_item_ops = {
+	.release                = acm_attr_release,
+	.show_attribute		= f_acm_attr_show,
+};
+
+static ssize_t f_acm_port_num_show(struct f_serial_opts *opts, char *page)
+{
+	return sprintf(page, "%u\n", opts->port_num);
+}
+
+static struct f_serial_opts_attribute f_acm_port_num =
+	__CONFIGFS_ATTR_RO(port_num, f_acm_port_num_show);
+
+
+static struct configfs_attribute *acm_attrs[] = {
+	&f_acm_port_num.attr,
+	NULL,
+};
+
+static struct config_item_type acm_func_type = {
+	.ct_item_ops    = &acm_item_ops,
+	.ct_attrs	= acm_attrs,
+	.ct_owner       = THIS_MODULE,
+};
+
 static void acm_free_instance(struct usb_function_instance *fi)
 {
 	struct f_serial_opts *opts;
@@ -786,6 +839,8 @@ static struct usb_function_instance *acm_alloc_instance(void)
 		kfree(opts);
 		return ERR_PTR(ret);
 	}
+	config_group_init_type_name(&opts->func_inst.group, "",
+			&acm_func_type);
 	return &opts->func_inst;
 }
 DECLARE_USB_FUNCTION_INIT(acm, acm_alloc_instance, acm_alloc_func);

include/linux/usb/composite.h

@@ -39,6 +39,7 @@
 #include <linux/usb/ch9.h>
 #include <linux/usb/gadget.h>
 #include <linux/log2.h>
+#include <linux/configfs.h>
 
 /*
  * USB function drivers should return USB_GADGET_DELAYED_STATUS if they
@@ -464,6 +465,8 @@ struct usb_function_driver {
 };
 
 struct usb_function_instance {
+	struct config_group group;
+	struct list_head cfs_list;
 	struct usb_function_driver *fd;
 	void (*free_func_inst)(struct usb_function_instance *inst);
 };

include/linux/usb/gadget_configfs.h

+#ifndef __GADGET_CONFIGFS__
+#define __GADGET_CONFIGFS__
+
+#include <linux/configfs.h>
+
+int check_user_usb_string(const char *name,
+		struct usb_gadget_strings *stringtab_dev);
+
+#define GS_STRINGS_W(__struct, __name)	\
+	static ssize_t __struct##_##__name##_store(struct __struct *gs, \
+		const char *page, size_t len)		\
+{							\
+	int ret;					\
+							\
+	ret = usb_string_copy(page, &gs->__name);	\
+	if (ret)					\
+		return ret;				\
+	return len;					\
+}
+
+#define GS_STRINGS_R(__struct, __name)	\
+	static ssize_t __struct##_##__name##_show(struct __struct *gs, \
+			char *page)	\
+{	\
+	return sprintf(page, "%s\n", gs->__name ?: "");	\
+}
+
+#define GS_STRING_ITEM_ATTR(struct_name, name)	\
+	static struct struct_name##_attribute struct_name##_##name = \
+		__CONFIGFS_ATTR(name,  S_IRUGO | S_IWUSR,		\
+				struct_name##_##name##_show,		\
+				struct_name##_##name##_store)
+
+#define GS_STRINGS_RW(struct_name, _name)	\
+	GS_STRINGS_R(struct_name, _name)	\
+	GS_STRINGS_W(struct_name, _name)	\
+	GS_STRING_ITEM_ATTR(struct_name, _name)
+
+#define USB_CONFIG_STRING_RW_OPS(struct_in)				\
+	CONFIGFS_ATTR_OPS(struct_in);					\
+									\
+static struct configfs_item_operations struct_in##_langid_item_ops = {	\
+	.release                = struct_in##_attr_release,		\
+	.show_attribute         = struct_in##_attr_show,		\
+	.store_attribute        = struct_in##_attr_store,		\
+};									\
+									\
+static struct config_item_type struct_in##_langid_type = {		\
+	.ct_item_ops	= &struct_in##_langid_item_ops,			\
+	.ct_attrs	= struct_in##_langid_attrs,			\
+	.ct_owner	= THIS_MODULE,					\
+}
+
+#define USB_CONFIG_STRINGS_LANG(struct_in, struct_member)	\
+	static struct config_group *struct_in##_strings_make(		\
+			struct config_group *group,			\
+			const char *name)				\
+	{								\
+	struct struct_member *gi;					\
+	struct struct_in *gs;						\
+	struct struct_in *new;						\
+	int langs = 0;							\
+	int ret;							\
+									\
+	new = kzalloc(sizeof(*new), GFP_KERNEL);			\
+	if (!new)							\
+		return ERR_PTR(-ENOMEM);				\
+									\
+	ret = check_user_usb_string(name, &new->stringtab_dev);		\
+	if (ret)							\
+		goto err;						\
+	config_group_init_type_name(&new->group, name,			\
+			&struct_in##_langid_type);			\
+									\
+	gi = container_of(group, struct struct_member, strings_group);	\
+	ret = -EEXIST;							\
+	list_for_each_entry(gs, &gi->string_list, list) {		\
+		if (gs->stringtab_dev.language == new->stringtab_dev.language) \
+			goto err;					\
+		langs++;						\
+	}								\
+	ret = -EOVERFLOW;						\
+	if (langs >= MAX_USB_STRING_LANGS)				\
+		goto err;						\
+									\
+	list_add_tail(&new->list, &gi->string_list);			\
+	return &new->group;						\
+err:									\
+	kfree(new);							\
+	return ERR_PTR(ret);						\
+}									\
+									\
+static void struct_in##_strings_drop(					\
+		struct config_group *group,				\
+		struct config_item *item)				\
+{									\
+	config_item_put(item);						\
+}									\
+									\
+static struct configfs_group_operations struct_in##_strings_ops = {	\
+	.make_group     = &struct_in##_strings_make,			\
+	.drop_item      = &struct_in##_strings_drop,			\
+};									\
+									\
+static struct config_item_type struct_in##_strings_type = {		\
+	.ct_group_ops   = &struct_in##_strings_ops,			\
+	.ct_owner       = THIS_MODULE,					\
+}
+
+#endif