- * - The first part of each comment specifies OpenFlow type/code for each
- * protocol that supports the error.
+ * - The first part of each comment specifies the vendor, OpenFlow versions,
+ * type, and sometimes a code for each protocol that supports the error:
+ *
+ * # The vendor is OF for standard OpenFlow error codes. Otherwise it
+ * is one of the *_VENDOR_ID codes defined in openflow-common.h.
+ *
+ * # The version can specify a specific OpenFlow version, a version
+ * range delimited by "-", or an open-ended range with "+".
+ *
+ * # Standard OpenFlow errors have both a type and a code. Extension
+ * errors generally have only a type, no code. There is one
+ * exception: Nicira extension (NX) errors for OpenFlow 1.0 and 1.1
+ * have both a type and a code. (This means that the version
+ * specification for NX errors may not include version 1.0 or 1.1 (or
+ * both) along with version 1.2 or later, because the requirements
+ * for those versions are different.)