usb: common: introduce usb_state_string()

this function will receive enum usb_device_state
and return a human-readable string from it or,
case an unknown value is passed as argument,
the string "UNKNOWN".
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/usb-common.c

@@ -32,4 +32,25 @@ const char *usb_speed_string(enum usb_device_speed speed)
 }
 EXPORT_SYMBOL_GPL(usb_speed_string);
 
+const char *usb_state_string(enum usb_device_state state)
+{
+	static const char *const names[] = {
+		[USB_STATE_NOTATTACHED] = "not attached",
+		[USB_STATE_ATTACHED] = "attached",
+		[USB_STATE_POWERED] = "powered",
+		[USB_STATE_RECONNECTING] = "reconnecting",
+		[USB_STATE_UNAUTHENTICATED] = "unauthenticated",
+		[USB_STATE_DEFAULT] = "default",
+		[USB_STATE_ADDRESS] = "addresssed",
+		[USB_STATE_CONFIGURED] = "configured",
+		[USB_STATE_SUSPENDED] = "suspended",
+	};
+
+	if (state < 0 || state >= ARRAY_SIZE(names))
+		return "UNKNOWN";
+
+	return names[state];
+}
+EXPORT_SYMBOL_GPL(usb_state_string);
+
 MODULE_LICENSE("GPL");

include/linux/usb/ch9.h

@@ -43,4 +43,13 @@
  */
 extern const char *usb_speed_string(enum usb_device_speed speed);
 
+
+/**
+ * usb_state_string - Returns human readable name for the state.
+ * @state: The state to return a human-readable name for. If it's not
+ *	any of the states devices in usb_device_state_string enum,
+ *	the string UNKNOWN will be returned.
+ */
+extern const char *usb_state_string(enum usb_device_state state);
+
 #endif /* __LINUX_USB_CH9_H */