USB: gadget: composite: usb_string_ids_*() functions added

usb_string_ids_tab() and usb_string_ids_n() functions added to
the composite framework.  The first accepts an array of
usb_string object and for each registeres a string id and the
second registeres a given number of ids and returns the first.

This may simplify string ids registration since gadgets and
composite functions won't have to call usb_string_id() several
times and each time check for errer status -- all this will be
done with a single call.

Signed-off-by: Michal Nazarewicz <m.nazarewicz@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/gadget/composite.c

@@ -673,20 +673,83 @@ static int get_string(struct usb_composite_dev *cdev,
  * string IDs.  Drivers for functions, configurations, or gadgets will
  * then store that ID in the appropriate descriptors and string table.
  *
- * All string identifier should be allocated using this routine, to
+ * All string identifier should be allocated using this,
- * ensure that for example different functions don't wrongly assign
+ * @usb_string_ids_tab() or @usb_string_ids_n() routine, to ensure
- * different meanings to the same identifier.
+ * that for example different functions don't wrongly assign different
+ * meanings to the same identifier.
  */
 int usb_string_id(struct usb_composite_dev *cdev)
 {
 	if (cdev->next_string_id < 254) {
-		/* string id 0 is reserved */
+		/* string id 0 is reserved by USB spec for list of
+		 * supported languages */
+		/* 255 reserved as well? -- mina86 */
 		cdev->next_string_id++;
 		return cdev->next_string_id;
 	}
 	return -ENODEV;
 }
 
+/**
+ * usb_string_ids() - allocate unused string IDs in batch
+ * @cdev: the device whose string descriptor IDs are being allocated
+ * @str: an array of usb_string objects to assign numbers to
+ * Context: single threaded during gadget setup
+ *
+ * @usb_string_ids() is called from bind() callbacks to allocate
+ * string IDs.  Drivers for functions, configurations, or gadgets will
+ * then copy IDs from the string table to the appropriate descriptors
+ * and string table for other languages.
+ *
+ * All string identifier should be allocated using this,
+ * @usb_string_id() or @usb_string_ids_n() routine, to ensure that for
+ * example different functions don't wrongly assign different meanings
+ * to the same identifier.
+ */
+int usb_string_ids_tab(struct usb_composite_dev *cdev, struct usb_string *str)
+{
+	int next = cdev->next_string_id;
+
+	for (; str->s; ++str) {
+		if (unlikely(next >= 254))
+			return -ENODEV;
+		str->id = ++next;
+	}
+
+	cdev->next_string_id = next;
+
+	return 0;
+}
+
+/**
+ * usb_string_ids_n() - allocate unused string IDs in batch
+ * @cdev: the device whose string descriptor IDs are being allocated
+ * @n: number of string IDs to allocate
+ * Context: single threaded during gadget setup
+ *
+ * Returns the first requested ID.  This ID and next @n-1 IDs are now
+ * valid IDs.  At least providind that @n is non zore because if it
+ * is, returns last requested ID which is now very useful information.
+ *
+ * @usb_string_ids_n() is called from bind() callbacks to allocate
+ * string IDs.  Drivers for functions, configurations, or gadgets will
+ * then store that ID in the appropriate descriptors and string table.
+ *
+ * All string identifier should be allocated using this,
+ * @usb_string_id() or @usb_string_ids_n() routine, to ensure that for
+ * example different functions don't wrongly assign different meanings
+ * to the same identifier.
+ */
+int usb_string_ids_n(struct usb_composite_dev *c, unsigned n)
+{
+	unsigned next = c->next_string_id;
+	if (unlikely(n > 254 || (unsigned)next + n > 254))
+		return -ENODEV;
+	c->next_string_id += n;
+	return next + 1;
+}
+
+
 /*-------------------------------------------------------------------------*/
 
 static void composite_setup_complete(struct usb_ep *ep, struct usb_request *req)

include/linux/usb/composite.h

@@ -342,6 +342,10 @@ struct usb_composite_dev {
 };
 
 extern int usb_string_id(struct usb_composite_dev *c);
+extern int usb_string_ids_tab(struct usb_composite_dev *c,
+			      struct usb_string *str);
+extern int usb_string_ids_n(struct usb_composite_dev *c, unsigned n);
+
 
 /* messaging utils */
 #define DBG(d, fmt, args...) \