1 files changed, 75 insertions, 1 deletions

diff --git a/drivers/usb/gadget/config.c b/drivers/usb/gadget/config.c
index a4e54b2743f0..1ca1c326392a 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;
+}