usb: gadget: make sure each gadget is using same index for Product, Serial,…

The index in usb_string array is defined by the gadget. The gadget can
choose which index entry it assigns for the serial number and which the
product name. The gadget has just to ensure that the descriptor contains
the proper string id which is assigned by composite.
If the composite layer knows the index of the "default" information
which will be overwritten by module parameters, it can be used later to
overwrite it.

Acked-by: Michal Nazarewicz <mina86@mina86.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Felipe Balbi <balbi@ti.com>

17 files changed, 95 insertions, 118 deletions

diff --git a/drivers/usb/gadget/acm_ms.c b/drivers/usb/gadget/acm_ms.c
index 7bd6b71af5d..35db6aa5728 100644
--- a/drivers/usb/gadget/acm_ms.c
+++ b/drivers/usb/gadget/acm_ms.c
@@ -90,14 +90,12 @@ static const struct usb_descriptor_header *otg_desc[] = {
 
 /* string IDs are assigned dynamically */
 
-#define STRING_MANUFACTURER_IDX		0
-#define STRING_PRODUCT_IDX		1
-
 static char manufacturer[50];
 
 static struct usb_string strings_dev[] = {
-	[STRING_MANUFACTURER_IDX].s = manufacturer,
-	[STRING_PRODUCT_IDX].s = DRIVER_DESC,
+	[USB_GADGET_MANUFACTURER_IDX].s = manufacturer,
+	[USB_GADGET_PRODUCT_IDX].s = DRIVER_DESC,
+	[USB_GADGET_SERIAL_IDX].s = "",
 	{  } /* end of list */
 };
 
@@ -196,8 +194,8 @@ static int __init acm_ms_bind(struct usb_composite_dev *cdev)
 	status = usb_string_ids_tab(cdev, strings_dev);
 	if (status < 0)
 		goto fail1;
-	device_desc.iManufacturer = strings_dev[STRING_MANUFACTURER_IDX].id;
-	device_desc.iProduct = strings_dev[STRING_PRODUCT_IDX].id;
+	device_desc.iManufacturer = strings_dev[USB_GADGET_MANUFACTURER_IDX].id;
+	device_desc.iProduct = strings_dev[USB_GADGET_PRODUCT_IDX].id;
 
 	/* register our configuration */
 	status = usb_add_config(cdev, &acm_ms_config_driver, acm_ms_do_config);
diff --git a/drivers/usb/gadget/audio.c b/drivers/usb/gadget/audio.c
index 55b593c5a9c..8857b6eeb6a 100644
--- a/drivers/usb/gadget/audio.c
+++ b/drivers/usb/gadget/audio.c
@@ -33,14 +33,12 @@ USB_GADGET_COMPOSITE_OPTIONS();
 
 /* string IDs are assigned dynamically */
 
-#define STRING_MANUFACTURER_IDX		0
-#define STRING_PRODUCT_IDX		1
-
 static char manufacturer[50];
 
 static struct usb_string strings_dev[] = {
-	[STRING_MANUFACTURER_IDX].s = manufacturer,
-	[STRING_PRODUCT_IDX].s = DRIVER_DESC,
+	[USB_GADGET_MANUFACTURER_IDX].s = manufacturer,
+	[USB_GADGET_PRODUCT_IDX].s = DRIVER_DESC,
+	[USB_GADGET_SERIAL_IDX].s = "",
 	{  } /* end of list */
 };
 
@@ -170,8 +168,8 @@ static int __init audio_bind(struct usb_composite_dev *cdev)
 	status = usb_string_ids_tab(cdev, strings_dev);
 	if (status < 0)
 		goto fail;
-	device_desc.iManufacturer = strings_dev[STRING_MANUFACTURER_IDX].id;
-	device_desc.iProduct = strings_dev[STRING_PRODUCT_IDX].id;
+	device_desc.iManufacturer = strings_dev[USB_GADGET_MANUFACTURER_IDX].id;
+	device_desc.iProduct = strings_dev[USB_GADGET_PRODUCT_IDX].id;
 
 	status = usb_add_config(cdev, &audio_config_driver, audio_do_config);
 	if (status < 0)
diff --git a/drivers/usb/gadget/cdc2.c b/drivers/usb/gadget/cdc2.c
index 93a75809b4d..8966bdec153 100644
--- a/drivers/usb/gadget/cdc2.c
+++ b/drivers/usb/gadget/cdc2.c
@@ -90,15 +90,12 @@ static const struct usb_descriptor_header *otg_desc[] = {
 
 
 /* string IDs are assigned dynamically */
-
-#define STRING_MANUFACTURER_IDX		0
-#define STRING_PRODUCT_IDX		1
-
 static char manufacturer[50];
 
 static struct usb_string strings_dev[] = {
-	[STRING_MANUFACTURER_IDX].s = manufacturer,
-	[STRING_PRODUCT_IDX].s = DRIVER_DESC,
+	[USB_GADGET_MANUFACTURER_IDX].s = manufacturer,
+	[USB_GADGET_PRODUCT_IDX].s = DRIVER_DESC,
+	[USB_GADGET_SERIAL_IDX].s = "",
 	{  } /* end of list */
 };
 
@@ -197,8 +194,8 @@ static int __init cdc_bind(struct usb_composite_dev *cdev)
 	status = usb_string_ids_tab(cdev, strings_dev);
 	if (status < 0)
 		goto fail1;
-	device_desc.iManufacturer = strings_dev[STRING_MANUFACTURER_IDX].id;
-	device_desc.iProduct = strings_dev[STRING_PRODUCT_IDX].id;
+	device_desc.iManufacturer = strings_dev[USB_GADGET_MANUFACTURER_IDX].id;
+	device_desc.iProduct = strings_dev[USB_GADGET_PRODUCT_IDX].id;
 
 	/* register our configuration */
 	status = usb_add_config(cdev, &cdc_config_driver, cdc_do_config);
diff --git a/drivers/usb/gadget/ether.c b/drivers/usb/gadget/ether.c
index 709ef226559..dd5e00d207f 100644
--- a/drivers/usb/gadget/ether.c
+++ b/drivers/usb/gadget/ether.c
@@ -193,17 +193,13 @@ static const struct usb_descriptor_header *otg_desc[] = {
 	NULL,
 };
 
-
 /* string IDs are assigned dynamically */
-
-#define STRING_MANUFACTURER_IDX		0
-#define STRING_PRODUCT_IDX		1
-
 static char manufacturer[50];
 
 static struct usb_string strings_dev[] = {
-	[STRING_MANUFACTURER_IDX].s = manufacturer,
-	[STRING_PRODUCT_IDX].s = PREFIX DRIVER_DESC,
+	[USB_GADGET_MANUFACTURER_IDX].s = manufacturer,
+	[USB_GADGET_PRODUCT_IDX].s = PREFIX DRIVER_DESC,
+	[USB_GADGET_SERIAL_IDX].s = "",
 	{  } /* end of list */
 };
 
@@ -349,8 +345,8 @@ static int __init eth_bind(struct usb_composite_dev *cdev)
 	status = usb_string_ids_tab(cdev, strings_dev);
 	if (status < 0)
 		goto fail;
-	device_desc.iManufacturer = strings_dev[STRING_MANUFACTURER_IDX].id;
-	device_desc.iProduct = strings_dev[STRING_PRODUCT_IDX].id;
+	device_desc.iManufacturer = strings_dev[USB_GADGET_MANUFACTURER_IDX].id;
+	device_desc.iProduct = strings_dev[USB_GADGET_PRODUCT_IDX].id;
 
 	/* register our configuration(s); RNDIS first, if it's used */
 	if (has_rndis()) {
diff --git a/drivers/usb/gadget/g_ffs.c b/drivers/usb/gadget/g_ffs.c
index a44ed661c16..16d18873ebe 100644
--- a/drivers/usb/gadget/g_ffs.c
+++ b/drivers/usb/gadget/g_ffs.c
@@ -116,6 +116,9 @@ static const struct usb_descriptor_header *gfs_otg_desc[] = {
 
 /* String IDs are assigned dynamically */
 static struct usb_string gfs_strings[] = {
+	[USB_GADGET_MANUFACTURER_IDX].s = "",
+	[USB_GADGET_PRODUCT_IDX].s = "",
+	[USB_GADGET_SERIAL_IDX].s = "",
 #ifdef CONFIG_USB_FUNCTIONFS_RNDIS
 	{ .s = "FunctionFS + RNDIS" },
 #endif
@@ -369,9 +372,10 @@ static int gfs_bind(struct usb_composite_dev *cdev)
 
 	for (i = 0; i < ARRAY_SIZE(gfs_configurations); ++i) {
 		struct gfs_configuration *c = gfs_configurations + i;
+		int sid = USB_GADGET_FIRST_AVAIL_IDX + i;
 
-		c->c.label			= gfs_strings[i].s;
-		c->c.iConfiguration		= gfs_strings[i].id;
+		c->c.label			= gfs_strings[sid].s;
+		c->c.iConfiguration		= gfs_strings[sid].id;
 		c->c.bConfigurationValue	= 1 + i;
 		c->c.bmAttributes		= USB_CONFIG_ATT_SELFPOWER;
 
diff --git a/drivers/usb/gadget/gmidi.c b/drivers/usb/gadget/gmidi.c
index 01b31e2d03a..2ee3a74056c 100644
--- a/drivers/usb/gadget/gmidi.c
+++ b/drivers/usb/gadget/gmidi.c
@@ -84,9 +84,7 @@ MODULE_PARM_DESC(out_ports, "Number of MIDI output ports");
 
 /* string IDs are assigned dynamically */
 
-#define STRING_MANUFACTURER_IDX		0
-#define STRING_PRODUCT_IDX		1
-#define STRING_DESCRIPTION_IDX		2
+#define STRING_DESCRIPTION_IDX		USB_GADGET_FIRST_AVAIL_IDX
 
 static struct usb_device_descriptor device_desc = {
 	.bLength =		USB_DT_DEVICE_SIZE,
@@ -101,8 +99,9 @@ static struct usb_device_descriptor device_desc = {
 };
 
 static struct usb_string strings_dev[] = {
-	[STRING_MANUFACTURER_IDX].s	= "Grey Innovation",
-	[STRING_PRODUCT_IDX].s		= "MIDI Gadget",
+	[USB_GADGET_MANUFACTURER_IDX].s	= "Grey Innovation",
+	[USB_GADGET_PRODUCT_IDX].s	= "MIDI Gadget",
+	[USB_GADGET_SERIAL_IDX].s	= "",
 	[STRING_DESCRIPTION_IDX].s	= "MIDI",
 	{  } /* end of list */
 };
@@ -145,8 +144,8 @@ static int __init midi_bind(struct usb_composite_dev *cdev)
 	status = usb_string_ids_tab(cdev, strings_dev);
 	if (status < 0)
 		return status;
-	device_desc.iManufacturer = strings_dev[STRING_MANUFACTURER_IDX].id;
-	device_desc.iProduct = strings_dev[STRING_PRODUCT_IDX].id;
+	device_desc.iManufacturer = strings_dev[USB_GADGET_MANUFACTURER_IDX].id;
+	device_desc.iProduct = strings_dev[USB_GADGET_PRODUCT_IDX].id;
 	midi_config.iConfiguration = strings_dev[STRING_DESCRIPTION_IDX].id;
 
 	gcnum = usb_gadget_controller_number(gadget);
diff --git a/drivers/usb/gadget/hid.c b/drivers/usb/gadget/hid.c
index 59fe7eef00d..16caf50e916 100644
--- a/drivers/usb/gadget/hid.c
+++ b/drivers/usb/gadget/hid.c
@@ -91,15 +91,12 @@ static const struct usb_descriptor_header *otg_desc[] = {
 
 
 /* string IDs are assigned dynamically */
-
-#define STRING_MANUFACTURER_IDX		0
-#define STRING_PRODUCT_IDX		1
-
 static char manufacturer[50];
 
 static struct usb_string strings_dev[] = {
-	[STRING_MANUFACTURER_IDX].s = manufacturer,
-	[STRING_PRODUCT_IDX].s = DRIVER_DESC,
+	[USB_GADGET_MANUFACTURER_IDX].s = manufacturer,
+	[USB_GADGET_PRODUCT_IDX].s = DRIVER_DESC,
+	[USB_GADGET_SERIAL_IDX].s = "",
 	{  } /* end of list */
 };
 
@@ -181,8 +178,8 @@ static int __init hid_bind(struct usb_composite_dev *cdev)
 	status = usb_string_ids_tab(cdev, strings_dev);
 	if (status < 0)
 		return status;
-	device_desc.iManufacturer = strings_dev[STRING_MANUFACTURER_IDX].id;
-	device_desc.iProduct = strings_dev[STRING_PRODUCT_IDX].id;
+	device_desc.iManufacturer = strings_dev[USB_GADGET_MANUFACTURER_IDX].id;
+	device_desc.iProduct = strings_dev[USB_GADGET_PRODUCT_IDX].id;
 
 	/* register our configuration */
 	status = usb_add_config(cdev, &config_driver, do_config);
diff --git a/drivers/usb/gadget/multi.c b/drivers/usb/gadget/multi.c
index 60168877330..94b35e5539d 100644
--- a/drivers/usb/gadget/multi.c
+++ b/drivers/usb/gadget/multi.c
@@ -109,21 +109,16 @@ static const struct usb_descriptor_header *otg_desc[] = {
 
 
 enum {
-#ifdef CONFIG_USB_G_MULTI_RNDIS
-	MULTI_STRING_RNDIS_CONFIG_IDX,
-#endif
-#ifdef CONFIG_USB_G_MULTI_CDC
+	MULTI_STRING_RNDIS_CONFIG_IDX = USB_GADGET_FIRST_AVAIL_IDX,
 	MULTI_STRING_CDC_CONFIG_IDX,
-#endif
 };
 
 static struct usb_string strings_dev[] = {
-#ifdef CONFIG_USB_G_MULTI_RNDIS
+	[USB_GADGET_MANUFACTURER_IDX].s = "",
+	[USB_GADGET_PRODUCT_IDX].s = "",
+	[USB_GADGET_SERIAL_IDX].s = "",
 	[MULTI_STRING_RNDIS_CONFIG_IDX].s = "Multifunction with RNDIS",
-#endif
-#ifdef CONFIG_USB_G_MULTI_CDC
 	[MULTI_STRING_CDC_CONFIG_IDX].s   = "Multifunction with CDC ECM",
-#endif
 	{  } /* end of list */
 };
 
diff --git a/drivers/usb/gadget/ncm.c b/drivers/usb/gadget/ncm.c
index 8537cd9c6af..1a26452ce4c 100644
--- a/drivers/usb/gadget/ncm.c
+++ b/drivers/usb/gadget/ncm.c
@@ -97,15 +97,12 @@ static const struct usb_descriptor_header *otg_desc[] = {
 
 
 /* string IDs are assigned dynamically */
-
-#define STRING_MANUFACTURER_IDX		0
-#define STRING_PRODUCT_IDX		1
-
 static char manufacturer[50];
 
 static struct usb_string strings_dev[] = {
-	[STRING_MANUFACTURER_IDX].s = manufacturer,
-	[STRING_PRODUCT_IDX].s = DRIVER_DESC,
+	[USB_GADGET_MANUFACTURER_IDX].s = manufacturer,
+	[USB_GADGET_PRODUCT_IDX].s = DRIVER_DESC,
+	[USB_GADGET_SERIAL_IDX].s = "",
 	{  } /* end of list */
 };
 
@@ -184,8 +181,8 @@ static int __init gncm_bind(struct usb_composite_dev *cdev)
 	status = usb_string_ids_tab(cdev, strings_dev);
 	if (status < 0)
 		goto fail;
-	device_desc.iManufacturer = strings_dev[STRING_MANUFACTURER_IDX].id;
-	device_desc.iProduct = strings_dev[STRING_PRODUCT_IDX].id;
+	device_desc.iManufacturer = strings_dev[USB_GADGET_MANUFACTURER_IDX].id;
+	device_desc.iProduct = strings_dev[USB_GADGET_PRODUCT_IDX].id;
 
 	status = usb_add_config(cdev, &ncm_config_driver,
 				ncm_do_config);
diff --git a/drivers/usb/gadget/nokia.c b/drivers/usb/gadget/nokia.c
index 5ed927b16c0..34b97f12b7d 100644
--- a/drivers/usb/gadget/nokia.c
+++ b/drivers/usb/gadget/nokia.c
@@ -56,17 +56,16 @@ USB_GADGET_COMPOSITE_OPTIONS();
 
 /* string IDs are assigned dynamically */
 
-#define STRING_MANUFACTURER_IDX		0
-#define STRING_PRODUCT_IDX		1
-#define STRING_DESCRIPTION_IDX		2
+#define STRING_DESCRIPTION_IDX		USB_GADGET_FIRST_AVAIL_IDX
 
 static char manufacturer_nokia[] = "Nokia";
 static const char product_nokia[] = NOKIA_LONG_NAME;
 static const char description_nokia[] = "PC-Suite Configuration";
 
 static struct usb_string strings_dev[] = {
-	[STRING_MANUFACTURER_IDX].s = manufacturer_nokia,
-	[STRING_PRODUCT_IDX].s = NOKIA_LONG_NAME,
+	[USB_GADGET_MANUFACTURER_IDX].s = manufacturer_nokia,
+	[USB_GADGET_PRODUCT_IDX].s = NOKIA_LONG_NAME,
+	[USB_GADGET_SERIAL_IDX].s = "",
 	[STRING_DESCRIPTION_IDX].s = description_nokia,
 	{  } /* end of list */
 };
@@ -168,8 +167,8 @@ static int __init nokia_bind(struct usb_composite_dev *cdev)
 	status = usb_string_ids_tab(cdev, strings_dev);
 	if (status < 0)
 		goto err_usb;
-	device_desc.iManufacturer = strings_dev[STRING_MANUFACTURER_IDX].id;
-	device_desc.iProduct = strings_dev[STRING_PRODUCT_IDX].id;
+	device_desc.iManufacturer = strings_dev[USB_GADGET_MANUFACTURER_IDX].id;
+	device_desc.iProduct = strings_dev[USB_GADGET_PRODUCT_IDX].id;
 	status = strings_dev[STRING_DESCRIPTION_IDX].id;
 	nokia_config_500ma_driver.iConfiguration = status;
 	nokia_config_100ma_driver.iConfiguration = status;
diff --git a/drivers/usb/gadget/printer.c b/drivers/usb/gadget/printer.c
index 3fa4d80629c..f02434a10de 100644
--- a/drivers/usb/gadget/printer.c
+++ b/drivers/usb/gadget/printer.c
@@ -139,10 +139,6 @@ module_param(qlen, uint, S_IRUGO|S_IWUSR);
  * descriptors are built on demand.
  */
 
-#define STRING_MANUFACTURER		0
-#define STRING_PRODUCT			1
-#define STRING_SERIALNUM		2
-
 /* holds our biggest descriptor */
 #define USB_DESC_BUFSIZE		256
 #define USB_BUFSIZE			8192
@@ -250,9 +246,9 @@ static char				pnp_string [1024] =
 
 /* static strings, in UTF-8 */
 static struct usb_string		strings [] = {
-	[STRING_MANUFACTURER].s = manufacturer,
-	[STRING_PRODUCT].s = product_desc,
-	[STRING_SERIALNUM].s =	serial_num,
+	[USB_GADGET_MANUFACTURER_IDX].s = manufacturer,
+	[USB_GADGET_PRODUCT_IDX].s = product_desc,
+	[USB_GADGET_SERIAL_IDX].s =	serial_num,
 	{  }		/* end of list */
 };
 
@@ -1261,9 +1257,9 @@ static int __init printer_bind(struct usb_composite_dev *cdev)
 	ret = usb_string_ids_tab(cdev, strings);
 	if (ret < 0)
 		return ret;
-	device_desc.iManufacturer = strings[STRING_MANUFACTURER].id;
-	device_desc.iProduct = strings[STRING_PRODUCT].id;
-	device_desc.iSerialNumber = strings[STRING_SERIALNUM].id;
+	device_desc.iManufacturer = strings[USB_GADGET_MANUFACTURER_IDX].id;
+	device_desc.iProduct = strings[USB_GADGET_PRODUCT_IDX].id;
+	device_desc.iSerialNumber = strings[USB_GADGET_SERIAL_IDX].id;
 
 	ret = usb_add_config(cdev, &printer_cfg_driver, printer_bind_config);
 	if (ret)
diff --git a/drivers/usb/gadget/serial.c b/drivers/usb/gadget/serial.c
index 27b5ce939bd..768a38e896f 100644
--- a/drivers/usb/gadget/serial.c
+++ b/drivers/usb/gadget/serial.c
@@ -59,15 +59,14 @@ USB_GADGET_COMPOSITE_OPTIONS();
 
 /* string IDs are assigned dynamically */
 
-#define STRING_MANUFACTURER_IDX		0
-#define STRING_PRODUCT_IDX		1
-#define STRING_DESCRIPTION_IDX		2
+#define STRING_DESCRIPTION_IDX		USB_GADGET_FIRST_AVAIL_IDX
 
 static char manufacturer[50];
 
 static struct usb_string strings_dev[] = {
-	[STRING_MANUFACTURER_IDX].s = manufacturer,
-	[STRING_PRODUCT_IDX].s = GS_VERSION_NAME,
+	[USB_GADGET_MANUFACTURER_IDX].s = manufacturer,
+	[USB_GADGET_PRODUCT_IDX].s = GS_VERSION_NAME,
+	[USB_GADGET_SERIAL_IDX].s = "",
 	[STRING_DESCRIPTION_IDX].s = NULL /* updated; f(use_acm) */,
 	{  } /* end of list */
 };
@@ -179,8 +178,8 @@ static int __init gs_bind(struct usb_composite_dev *cdev)
 	status = usb_string_ids_tab(cdev, strings_dev);
 	if (status < 0)
 		goto fail;
-	device_desc.iManufacturer = strings_dev[STRING_MANUFACTURER_IDX].id;
-	device_desc.iProduct = strings_dev[STRING_PRODUCT_IDX].id;
+	device_desc.iManufacturer = strings_dev[USB_GADGET_MANUFACTURER_IDX].id;
+	device_desc.iProduct = strings_dev[USB_GADGET_PRODUCT_IDX].id;
 	status = strings_dev[STRING_DESCRIPTION_IDX].id;
 	serial_config_driver.iConfiguration = status;
 
diff --git a/drivers/usb/gadget/tcm_usb_gadget.c b/drivers/usb/gadget/tcm_usb_gadget.c
index fa3137ef228..b56d57d5979 100644
--- a/drivers/usb/gadget/tcm_usb_gadget.c
+++ b/drivers/usb/gadget/tcm_usb_gadget.c
@@ -2210,9 +2210,9 @@ static struct usb_device_descriptor usbg_device_desc = {
 };
 
 static struct usb_string	usbg_us_strings[] = {
-	[USB_G_STR_MANUFACTOR].s	= "Target Manufactor",
-	[USB_G_STR_PRODUCT].s		= "Target Product",
-	[USB_G_STR_SERIAL].s		= "000000000001",
+	[USB_GADGET_MANUFACTURER_IDX].s	= "Target Manufactor",
+	[USB_GADGET_PRODUCT_IDX].s	= "Target Product",
+	[USB_GADGET_SERIAL_IDX].s	= "000000000001",
 	[USB_G_STR_CONFIG].s		= "default config",
 	[USB_G_STR_INT_UAS].s		= "USB Attached SCSI",
 	[USB_G_STR_INT_BBB].s		= "Bulk Only Transport",
@@ -2431,9 +2431,10 @@ static int usb_target_bind(struct usb_composite_dev *cdev)
 		return ret;
 
 	usbg_device_desc.iManufacturer =
-		usbg_us_strings[USB_G_STR_MANUFACTOR].id;
-	usbg_device_desc.iProduct = usbg_us_strings[USB_G_STR_PRODUCT].id;
-	usbg_device_desc.iSerialNumber = usbg_us_strings[USB_G_STR_SERIAL].id;
+		usbg_us_strings[USB_GADGET_MANUFACTURER_IDX].id;
+	usbg_device_desc.iProduct = usbg_us_strings[USB_GADGET_PRODUCT_IDX].id;
+	usbg_device_desc.iSerialNumber =
+		usbg_us_strings[USB_GADGET_SERIAL_IDX].id;
 	usbg_config_driver.iConfiguration =
 		usbg_us_strings[USB_G_STR_CONFIG].id;
 
diff --git a/drivers/usb/gadget/tcm_usb_gadget.h b/drivers/usb/gadget/tcm_usb_gadget.h
index 9d32ec30f4e..8289219925b 100644
--- a/drivers/usb/gadget/tcm_usb_gadget.h
+++ b/drivers/usb/gadget/tcm_usb_gadget.h
@@ -17,10 +17,7 @@
 #define UASP_SS_EP_COMP_NUM_STREAMS (1 << UASP_SS_EP_COMP_LOG_STREAMS)
 
 enum {
-	USB_G_STR_MANUFACTOR,
-	USB_G_STR_PRODUCT,
-	USB_G_STR_SERIAL,
-	USB_G_STR_CONFIG,
+	USB_G_STR_CONFIG = USB_GADGET_FIRST_AVAIL_IDX,
 	USB_G_STR_INT_UAS,
 	USB_G_STR_INT_BBB,
 };
diff --git a/drivers/usb/gadget/webcam.c b/drivers/usb/gadget/webcam.c
index 306006419f3..03591194b17 100644
--- a/drivers/usb/gadget/webcam.c
+++ b/drivers/usb/gadget/webcam.c
@@ -45,13 +45,12 @@ static char webcam_config_label[] = "Video";
 
 /* string IDs are assigned dynamically */
 
-#define STRING_MANUFACTURER_IDX		0
-#define STRING_PRODUCT_IDX		1
-#define STRING_DESCRIPTION_IDX		2
+#define STRING_DESCRIPTION_IDX		USB_GADGET_FIRST_AVAIL_IDX
 
 static struct usb_string webcam_strings[] = {
-	[STRING_MANUFACTURER_IDX].s = webcam_vendor_label,
-	[STRING_PRODUCT_IDX].s = webcam_product_label,
+	[USB_GADGET_MANUFACTURER_IDX].s = webcam_vendor_label,
+	[USB_GADGET_PRODUCT_IDX].s = webcam_product_label,
+	[USB_GADGET_SERIAL_IDX].s = "",
 	[STRING_DESCRIPTION_IDX].s = webcam_config_label,
 	{  }
 };
@@ -360,9 +359,9 @@ webcam_bind(struct usb_composite_dev *cdev)
 	if (ret < 0)
 		goto error;
 	webcam_device_descriptor.iManufacturer =
-		webcam_strings[STRING_MANUFACTURER_IDX].id;
+		webcam_strings[USB_GADGET_MANUFACTURER_IDX].id;
 	webcam_device_descriptor.iProduct =
-		webcam_strings[STRING_PRODUCT_IDX].id;
+		webcam_strings[USB_GADGET_PRODUCT_IDX].id;
 	webcam_config_driver.iConfiguration =
 		webcam_strings[STRING_DESCRIPTION_IDX].id;
 
diff --git a/drivers/usb/gadget/zero.c b/drivers/usb/gadget/zero.c
index 2b31a4ae26b..ee769c45498 100644
--- a/drivers/usb/gadget/zero.c
+++ b/drivers/usb/gadget/zero.c
@@ -139,20 +139,15 @@ const struct usb_descriptor_header *otg_desc[] = {
 #endif
 
 /* string IDs are assigned dynamically */
-
-#define STRING_MANUFACTURER_IDX		0
-#define STRING_PRODUCT_IDX		1
-#define STRING_SERIAL_IDX		2
-
 static char manufacturer[50];
 
 /* default serial number takes at least two packets */
 static char serial[] = "0123456789.0123456789.0123456789";
 
 static struct usb_string strings_dev[] = {
-	[STRING_MANUFACTURER_IDX].s = manufacturer,
-	[STRING_PRODUCT_IDX].s = longname,
-	[STRING_SERIAL_IDX].s = serial,
+	[USB_GADGET_MANUFACTURER_IDX].s = manufacturer,
+	[USB_GADGET_PRODUCT_IDX].s = longname,
+	[USB_GADGET_SERIAL_IDX].s = serial,
 	{  }			/* end of list */
 };
 
@@ -274,9 +269,9 @@ static int __init zero_bind(struct usb_composite_dev *cdev)
 	if (status < 0)
 		return status;
 
-	device_desc.iManufacturer = strings_dev[STRING_MANUFACTURER_IDX].id;
-	device_desc.iProduct = strings_dev[STRING_PRODUCT_IDX].id;
-	device_desc.iSerialNumber = strings_dev[STRING_SERIAL_IDX].id;
+	device_desc.iManufacturer = strings_dev[USB_GADGET_MANUFACTURER_IDX].id;
+	device_desc.iProduct = strings_dev[USB_GADGET_PRODUCT_IDX].id;
+	device_desc.iSerialNumber = strings_dev[USB_GADGET_SERIAL_IDX].id;
 
 	setup_timer(&autoresume_timer, zero_autoresume, (unsigned long) cdev);
 
diff --git a/include/linux/usb/composite.h b/include/linux/usb/composite.h
index 7651e5bf748..f821a3ad475 100644
--- a/include/linux/usb/composite.h
+++ b/include/linux/usb/composite.h
@@ -248,6 +248,14 @@ int usb_add_config(struct usb_composite_dev *,
 void usb_remove_config(struct usb_composite_dev *,
 		struct usb_configuration *);
 
+/* predefined index for usb_composite_driver */
+enum {
+	USB_GADGET_MANUFACTURER_IDX	= 0,
+	USB_GADGET_PRODUCT_IDX,
+	USB_GADGET_SERIAL_IDX,
+	USB_GADGET_FIRST_AVAIL_IDX,
+};
+
 /**
  * struct usb_composite_driver - groups configurations into a gadget
  * @name: For diagnostics, identifies the driver.
@@ -261,7 +269,9 @@ void usb_remove_config(struct usb_composite_dev *,
  * @dev: Template descriptor for the device, including default device
  *	identifiers.
  * @strings: tables of strings, keyed by identifiers assigned during @bind
- *	and language IDs provided in control requests
+ *	and language IDs provided in control requests. Note: The first entries
+ *	are predefined. The first entry that may be used is
+ *	USB_GADGET_FIRST_AVAIL_IDX
  * @max_speed: Highest speed the driver supports.
  * @needs_serial: set to 1 if the gadget needs userspace to provide
  * 	a serial number.  If one is not provided, warning will be printed.