usb: gadget: Add Interface Association Descriptor to ECM

Add IAD to bind the two interfaces of ECM so that it works properly
in composite gadget mode.
Signed-off-by: Thirupathi <thirupathi.chippakurthy@stericsson.com>
Signed-off-by: Praveena Nadahally <praveen.nadahally@stericsson.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/gadget/f_ecm.c

@@ -97,6 +97,20 @@ static inline unsigned ecm_bitrate(struct usb_gadget *g)
 
 /* interface descriptor: */
 
+static struct usb_interface_assoc_descriptor
+ecm_iad_descriptor = {
+	.bLength =		sizeof ecm_iad_descriptor,
+	.bDescriptorType =	USB_DT_INTERFACE_ASSOCIATION,
+
+	/* .bFirstInterface =	DYNAMIC, */
+	.bInterfaceCount =	2,	/* control + data */
+	.bFunctionClass =	USB_CLASS_COMM,
+	.bFunctionSubClass =	USB_CDC_SUBCLASS_ETHERNET,
+	.bFunctionProtocol =	USB_CDC_PROTO_NONE,
+	/* .iFunction =		DYNAMIC */
+};
+
+
 static struct usb_interface_descriptor ecm_control_intf = {
 	.bLength =		sizeof ecm_control_intf,
 	.bDescriptorType =	USB_DT_INTERFACE,
@@ -199,6 +213,7 @@ static struct usb_endpoint_descriptor fs_ecm_out_desc = {
 
 static struct usb_descriptor_header *ecm_fs_function[] = {
 	/* CDC ECM control descriptors */
+	(struct usb_descriptor_header *) &ecm_iad_descriptor,
 	(struct usb_descriptor_header *) &ecm_control_intf,
 	(struct usb_descriptor_header *) &ecm_header_desc,
 	(struct usb_descriptor_header *) &ecm_union_desc,
@@ -247,6 +262,7 @@ static struct usb_endpoint_descriptor hs_ecm_out_desc = {
 
 static struct usb_descriptor_header *ecm_hs_function[] = {
 	/* CDC ECM control descriptors */
+	(struct usb_descriptor_header *) &ecm_iad_descriptor,
 	(struct usb_descriptor_header *) &ecm_control_intf,
 	(struct usb_descriptor_header *) &ecm_header_desc,
 	(struct usb_descriptor_header *) &ecm_union_desc,
@@ -339,6 +355,7 @@ static struct usb_string ecm_string_defs[] = {
 	[0].s = "CDC Ethernet Control Model (ECM)",
 	[1].s = NULL /* DYNAMIC */,
 	[2].s = "CDC Ethernet Data",
+	[3].s = "CDC ECM",
 	{  } /* end of list */
 };
 
@@ -674,6 +691,7 @@ ecm_bind(struct usb_configuration *c, struct usb_function *f)
 	if (status < 0)
 		goto fail;
 	ecm->ctrl_id = status;
+	ecm_iad_descriptor.bFirstInterface = status;
 
 	ecm_control_intf.bInterfaceNumber = status;
 	ecm_union_desc.bMasterInterface0 = status;
@@ -864,6 +882,13 @@ ecm_bind_config(struct usb_configuration *c, u8 ethaddr[ETH_ALEN])
 			return status;
 		ecm_string_defs[1].id = status;
 		ecm_desc.iMACAddress = status;
+
+		/* IAD label */
+		status = usb_string_id(c->cdev);
+		if (status < 0)
+			return status;
+		ecm_string_defs[3].id = status;
+		ecm_iad_descriptor.iFunction = status;
 	}
 
 	/* allocate and initialize one new instance */