- * 0 if successful lookup
- * - EINVAL if the parameters are invalid.
- * - ENOENT if the key is not found.
+ * - A positive value that can be used by the caller as an offset into an
+ * array of user data. This value is unique for this key, and is the same
+ * value that was returned when the key was added.
+ * - -EINVAL if the parameters are invalid.
+ * - -ENOENT if the key is not found.