usb: gadget: uvc: Add fix for UVC compliance test suite's assertion 6.1.25 failure

As per the UVC compliance test suite's assertion 6.1.25, the `iFunction`
field of the Interface Association Descriptor (IAD) should the match the
`iInterface` field of the standard Video Control (VC) Interface Descriptor for
this Video Interface Collection (VIC).

This mandatory case is captured in section 3.11 of the
USB Video Class Compliance specification revision 1.1

This patch fixes this test assertion's failure and has been tested on
Linux FC16, WinXP, WIN7 and WIN8 High speed and Super Speed hosts
for successful enumeration.

Signed-off-by: Bhupesh Sharma <bhupesh.sharma@st.com>
[Merged the association and control string descriptors]
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Tested-by: Bhupesh Sharma <bhupesh.sharma@st.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/gadget/f_uvc.c

@@ -51,13 +51,11 @@ MODULE_PARM_DESC(streaming_maxburst, "0 - 15 (ss only)");
 
 /* string IDs are assigned dynamically */
 
-#define UVC_STRING_ASSOCIATION_IDX		0
-#define UVC_STRING_CONTROL_IDX			1
-#define UVC_STRING_STREAMING_IDX		2
+#define UVC_STRING_CONTROL_IDX			0
+#define UVC_STRING_STREAMING_IDX		1
 
 static struct usb_string uvc_en_us_strings[] = {
-	[UVC_STRING_ASSOCIATION_IDX].s = "UVC Camera",
-	[UVC_STRING_CONTROL_IDX].s = "Video Control",
+	[UVC_STRING_CONTROL_IDX].s = "UVC Camera",
 	[UVC_STRING_STREAMING_IDX].s = "Video Streaming",
 	{  }
 };
@@ -572,7 +570,7 @@ uvc_function_unbind(struct usb_configuration *c, struct usb_function *f)
 	uvc->control_ep->driver_data = NULL;
 	uvc->video.ep->driver_data = NULL;
 
-	uvc_en_us_strings[UVC_STRING_ASSOCIATION_IDX].id = 0;
+	uvc_en_us_strings[UVC_STRING_CONTROL_IDX].id = 0;
 	usb_ep_free_request(cdev->gadget->ep0, uvc->control_req);
 	kfree(uvc->control_buf);
 
@@ -796,12 +794,12 @@ uvc_bind_config(struct usb_configuration *c,
 	 * for the first UVC function. UVC functions beyond the first (if any)
 	 * will reuse the same IDs.
 	 */
-	if (uvc_en_us_strings[UVC_STRING_ASSOCIATION_IDX].id == 0) {
+	if (uvc_en_us_strings[UVC_STRING_CONTROL_IDX].id == 0) {
 		ret = usb_string_ids_tab(c->cdev, uvc_en_us_strings);
 		if (ret)
 			goto error;
 		uvc_iad.iFunction =
-			uvc_en_us_strings[UVC_STRING_ASSOCIATION_IDX].id;
+			uvc_en_us_strings[UVC_STRING_CONTROL_IDX].id;
 		uvc_control_intf.iInterface =
 			uvc_en_us_strings[UVC_STRING_CONTROL_IDX].id;
 		ret = uvc_en_us_strings[UVC_STRING_STREAMING_IDX].id;