usb: gadget: composite: add iSerialNumber to usb_composite_driver

Add iSerialNumber to usb_composite_driver to allow setting a default value.
This is useful when the module is compiled-in. Then the composite_bind
is executed at kernel boot and string id for iSerialNumber can be overridden
even if there is no iSerialNumber kernel commandline parameter.
If the string id is not overridden, then get_string will never attempt to
look for the alternative string contents using cdev->serial_override.
Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/gadget/composite.c

@@ -938,7 +938,7 @@ static int get_string(struct usb_composite_dev *cdev,
 	else if (cdev->product_override == id)
 		str = iProduct ?: composite->iProduct;
 	else if (cdev->serial_override == id)
-		str = iSerialNumber;
+		str = iSerialNumber ?: composite->iSerialNumber;
 	else
 		str = NULL;
 	if (str) {
@@ -1503,7 +1503,8 @@ static int composite_bind(struct usb_gadget *gadget)
 		cdev->product_override =
 			override_id(cdev, &cdev->desc.iProduct);
 
-	if (iSerialNumber)
+	if (iSerialNumber ||
+	    (!cdev->desc.iSerialNumber && composite->iSerialNumber))
 		cdev->serial_override =
 			override_id(cdev, &cdev->desc.iSerialNumber);
 

include/linux/usb/composite.h

@@ -253,6 +253,8 @@ void usb_remove_config(struct usb_composite_dev *,
  * @iManufacturer: Used as iManufacturer override if @dev->iManufacturer is
  *	not set. If NULL a default "<system> <release> with <udc>" value
  *	will be used.
+ * @iSerialNumber: Used as iSerialNumber override if @dev->iSerialNumber is
+ *	not set.
  * @dev: Template descriptor for the device, including default device
  *	identifiers.
  * @strings: tables of strings, keyed by identifiers assigned during bind()
@@ -283,6 +285,7 @@ struct usb_composite_driver {
 	const char				*name;
 	const char				*iProduct;
 	const char				*iManufacturer;
+	const char				*iSerialNumber;
 	const struct usb_device_descriptor	*dev;
 	struct usb_gadget_strings		**strings;
 	enum usb_device_speed			max_speed;