usb: introduce usb_ep_type_string() function

In some places, the code prints a human-readable USB endpoint
transfer type (e.g. "bulk"). This involves a switch statement
sometimes wrapped around in ({ ... }) block leading to code
repetition.
To make this scenario easier, here introduces usb_ep_type_string()
function, which returns a human-readable name of provided
endpoint type.
It also changes a few places switch was used to use this
new function.

Signed-off-by: Chunfeng Yun <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/usb/common/common.c

···
 #include <linux/usb/otg.h>
 #include <linux/of_platform.h>
 
+static const char *const ep_type_names[] = {
+	[USB_ENDPOINT_XFER_CONTROL] = "ctrl",
+	[USB_ENDPOINT_XFER_ISOC] = "isoc",
+	[USB_ENDPOINT_XFER_BULK] = "bulk",
+	[USB_ENDPOINT_XFER_INT] = "intr",
+};
+
+const char *usb_ep_type_string(int ep_type)
+{
+	if (ep_type < 0 || ep_type >= ARRAY_SIZE(ep_type_names))
+		return "unknown";
+
+	return ep_type_names[ep_type];
+}
+EXPORT_SYMBOL_GPL(usb_ep_type_string);
+
 const char *usb_otg_state_string(enum usb_otg_state state)
 {
 	static const char *const names[] = {

drivers/usb/core/hcd.c

···
 		/* kick hcd */
 		unlink1(hcd, urb, -ESHUTDOWN);
 		dev_dbg (hcd->self.controller,
-			"shutdown urb %pK ep%d%s%s\n",
+			"shutdown urb %pK ep%d%s-%s\n",
 			urb, usb_endpoint_num(&ep->desc),
 			is_in ? "in" : "out",
-			({	char *s;
-
-				 switch (usb_endpoint_type(&ep->desc)) {
-				 case USB_ENDPOINT_XFER_CONTROL:
-					s = ""; break;
-				 case USB_ENDPOINT_XFER_BULK:
-					s = "-bulk"; break;
-				 case USB_ENDPOINT_XFER_INT:
-					s = "-intr"; break;
-				 default:
-					s = "-iso"; break;
-				};
-				s;
-			}));
+			usb_ep_type_string(usb_endpoint_type(&ep->desc)));
 		usb_put_urb (urb);
 
 		/* list contents may have changed */

drivers/usb/gadget/udc/aspeed-vhub/epn.c

···
 static int ast_vhub_epn_enable(struct usb_ep* u_ep,
 			       const struct usb_endpoint_descriptor *desc)
 {
-	static const char *ep_type_string[] __maybe_unused = { "ctrl",
-							       "isoc",
-							       "bulk",
-							       "intr" };
 	struct ast_vhub_ep *ep = to_ast_ep(u_ep);
 	struct ast_vhub_dev *dev;
 	struct ast_vhub *vhub;
···
 	ep->epn.wedged = false;
 
 	EPDBG(ep, "Enabling [%s] %s num %d maxpacket=%d\n",
-	      ep->epn.is_in ? "in" : "out", ep_type_string[type],
+	      ep->epn.is_in ? "in" : "out", usb_ep_type_string(type),
 	      usb_endpoint_num(desc), maxpacket);
 
 	/* Can we use DMA descriptor mode ? */

drivers/usb/gadget/udc/dummy_hcd.c

···
 		_ep->name,
 		desc->bEndpointAddress & 0x0f,
 		(desc->bEndpointAddress & USB_DIR_IN) ? "in" : "out",
-		({ char *val;
-		 switch (usb_endpoint_type(desc)) {
-		 case USB_ENDPOINT_XFER_BULK:
-			 val = "bulk";
-			 break;
-		 case USB_ENDPOINT_XFER_ISOC:
-			 val = "iso";
-			 break;
-		 case USB_ENDPOINT_XFER_INT:
-			 val = "intr";
-			 break;
-		 default:
-			 val = "ctrl";
-			 break;
-		 } val; }),
+		usb_ep_type_string(usb_endpoint_type(desc)),
 		max, ep->stream_en ? "enabled" : "disabled");
 
 	/* at this point real hardware should be NAKing transfers

include/linux/usb/ch9.h

···
 #include <uapi/linux/usb/ch9.h>
 
 /**
+ * usb_ep_type_string() - Returns human readable-name of the endpoint type.
+ * @ep_type: The endpoint type to return human-readable name for.  If it's not
+ *   any of the types: USB_ENDPOINT_XFER_{CONTROL, ISOC, BULK, INT},
+ *   usually got by usb_endpoint_type(), the string 'unknown' will be returned.
+ */
+extern const char *usb_ep_type_string(int ep_type);
+
+/**
  * usb_speed_string() - Returns human readable-name of the speed.
  * @speed: The speed to return human-readable name for.  If it's not
  *   any of the speeds defined in usb_device_speed enum, string for