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>

1 files changed, 11 insertions, 1 deletions

diff --git a/include/linux/usb/composite.h b/include/linux/usb/composite.h
index 7651e5bf7487..f821a3ad475d 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.