[media] uvcvideo: Add iFunction or iInterface to device names

Permits distinguishing between two /dev/videoX entries from the same
physical UVC device (that naturally share the same iProduct name).

This change matches current Windows behavior by prioritizing iFunction
over iInterface, but unlike Windows it displays both iProduct and
iFunction/iInterface strings when both are available.
Signed-off-by: Peter Boström <pbos@google.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

drivers/media/usb/uvc/uvc_driver.c

@@ -2013,6 +2013,7 @@ static int uvc_probe(struct usb_interface *intf,
 {
 	struct usb_device *udev = interface_to_usbdev(intf);
 	struct uvc_device *dev;
+	int function;
 	int ret;
 
 	if (id->idVendor && id->idProduct)
@@ -2044,9 +2045,27 @@ static int uvc_probe(struct usb_interface *intf,
 		strlcpy(dev->name, udev->product, sizeof dev->name);
 	else
 		snprintf(dev->name, sizeof dev->name,
-			"UVC Camera (%04x:%04x)",
-			le16_to_cpu(udev->descriptor.idVendor),
-			le16_to_cpu(udev->descriptor.idProduct));
+			 "UVC Camera (%04x:%04x)",
+			 le16_to_cpu(udev->descriptor.idVendor),
+			 le16_to_cpu(udev->descriptor.idProduct));
+
+	/*
+	 * Add iFunction or iInterface to names when available as additional
+	 * distinguishers between interfaces. iFunction is prioritized over
+	 * iInterface which matches Windows behavior at the point of writing.
+	 */
+	if (intf->intf_assoc && intf->intf_assoc->iFunction != 0)
+		function = intf->intf_assoc->iFunction;
+	else
+		function = intf->cur_altsetting->desc.iInterface;
+	if (function != 0) {
+		size_t len;
+
+		strlcat(dev->name, ": ", sizeof(dev->name));
+		len = strlen(dev->name);
+		usb_string(udev, function, dev->name + len,
+			   sizeof(dev->name) - len);
+	}
 
 	/* Parse the Video Class control descriptor. */
 	if (uvc_parse_control(dev) < 0) {