+ (*) int (*preparse)(struct key_preparsed_payload *prep);
+
+ This optional method permits the key type to attempt to parse payload
+ before a key is created (add key) or the key semaphore is taken (update or
+ instantiate key). The structure pointed to by prep looks like:
+
+ struct key_preparsed_payload {
+ char *description;
+ void *type_data[2];
+ void *payload;
+ const void *data;
+ size_t datalen;
+ size_t quotalen;
+ };
+
+ Before calling the method, the caller will fill in data and datalen with
+ the payload blob parameters; quotalen will be filled in with the default
+ quota size from the key type and the rest will be cleared.
+
+ If a description can be proposed from the payload contents, that should be
+ attached as a string to the description field. This will be used for the
+ key description if the caller of add_key() passes NULL or "".
+
+ The method can attach anything it likes to type_data[] and payload. These
+ are merely passed along to the instantiate() or update() operations.
+
+ The method should return 0 if success ful or a negative error code
+ otherwise.
+
+
+ (*) void (*free_preparse)(struct key_preparsed_payload *prep);
+
+ This method is only required if the preparse() method is provided,
+ otherwise it is unused. It cleans up anything attached to the
+ description, type_data and payload fields of the key_preparsed_payload
+ struct as filled in by the preparse() method.
+
+
+ (*) int (*instantiate)(struct key *key, struct key_preparsed_payload *prep);