1 files changed, 75 insertions, 1 deletions

diff --git a/drivers/usb/gadget/config.c b/drivers/usb/gadget/config.c
index a4e54b2743f..1ca1c326392 100644
--- a/drivers/usb/gadget/config.c
+++ b/drivers/usb/gadget/config.c
@@ -96,7 +96,7 @@ int usb_gadget_config_buf(
 	/* config descriptor first */
 	if (length < USB_DT_CONFIG_SIZE || !desc)
 		return -EINVAL;
-	*cp = *config; 
+	*cp = *config;
 
 	/* then interface/endpoint/class/vendor/... */
 	len = usb_descriptor_fillbuf(USB_DT_CONFIG_SIZE + (u8*)buf,
@@ -115,3 +115,77 @@ int usb_gadget_config_buf(
 	return len;
 }
 
+/**
+ * usb_copy_descriptors - copy a vector of USB descriptors
+ * @src: null-terminated vector to copy
+ * Context: initialization code, which may sleep
+ *
+ * This makes a copy of a vector of USB descriptors.  Its primary use
+ * is to support usb_function objects which can have multiple copies,
+ * each needing different descriptors.  Functions may have static
+ * tables of descriptors, which are used as templates and customized
+ * with identifiers (for interfaces, strings, endpoints, and more)
+ * as needed by a given function instance.
+ */
+struct usb_descriptor_header **__init
+usb_copy_descriptors(struct usb_descriptor_header **src)
+{
+	struct usb_descriptor_header **tmp;
+	unsigned bytes;
+	unsigned n_desc;
+	void *mem;
+	struct usb_descriptor_header **ret;
+
+	/* count descriptors and their sizes; then add vector size */
+	for (bytes = 0, n_desc = 0, tmp = src; *tmp; tmp++, n_desc++)
+		bytes += (*tmp)->bLength;
+	bytes += (n_desc + 1) * sizeof(*tmp);
+
+	mem = kmalloc(bytes, GFP_KERNEL);
+	if (!mem)
+		return NULL;
+
+	/* fill in pointers starting at "tmp",
+	 * to descriptors copied starting at "mem";
+	 * and return "ret"
+	 */
+	tmp = mem;
+	ret = mem;
+	mem += (n_desc + 1) * sizeof(*tmp);
+	while (*src) {
+		memcpy(mem, *src, (*src)->bLength);
+		*tmp = mem;
+		tmp++;
+		mem += (*src)->bLength;
+		src++;
+	}
+	*tmp = NULL;
+
+	return ret;
+}
+
+/**
+ * usb_find_endpoint - find a copy of an endpoint descriptor
+ * @src: original vector of descriptors
+ * @copy: copy of @src
+ * @ep: endpoint descriptor found in @src
+ *
+ * This returns the copy of the @match descriptor made for @copy.  Its
+ * intended use is to help remembering the endpoint descriptor to use
+ * when enabling a given endpoint.
+ */
+struct usb_endpoint_descriptor *__init
+usb_find_endpoint(
+	struct usb_descriptor_header **src,
+	struct usb_descriptor_header **copy,
+	struct usb_endpoint_descriptor *match
+)
+{
+	while (*src) {
+		if (*src == (void *) match)
+			return (void *)*copy;
+		src++;
+		copy++;
+	}
+	return NULL;
+}