USB: add helper to convert USB error codes

This converts error codes specific to USB to generic error codes
that can be returned to user space. Tests showed that it is so small
that it is better inlined.
Signed-off-by: Oliver Neukum <oneukum@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/core/usb.h

@@ -122,6 +122,19 @@ static inline int is_usb_device_driver(struct device_driver *drv)
 			for_devices;
 }
 
+/* translate USB error codes to codes user space understands */
+static inline int usb_translate_errors(int error_code)
+{
+	switch (error_code) {
+	case 0:
+	case -ENOMEM:
+	case -ENODEV:
+		return error_code;
+	default:
+		return -EIO;
+	}
+}
+
 
 /* for labeling diagnostics */
 extern const char *usbcore_name;