Documentation.

1 files changed, 31 insertions, 0 deletions

diff --git a/conf/confbase.Y b/conf/confbase.Y
index 5da84b1e..1b18a979 100644
--- a/conf/confbase.Y
+++ b/conf/confbase.Y
@@ -6,6 +6,37 @@
  *	Can be freely distributed and used under the terms of the GNU GPL.
  */
 
+/**
+ * DOC: Parser
+ *
+ * Both the configuration and CLI commands are analysed using a syntax
+ * driven parser generated by the |bison| tool from a grammar which
+ * is constructed from information gathered from grammar snippets by
+ * the |gen_parser.m4| script.
+ *
+ * Grammar snippets are files (usually with extension |.Y|) contributed
+ * by various BIRD modules to provide information about syntax of their
+ * configuration and their CLI commands. Each snipped consists of several
+ * section, each of them starting with a special keyword: |CF_HDR| for
+ * a list of |#include| directives needed by the C code, |CF_DEFINES|
+ * for a list of C declarations, |CF_DECLS| for |bison| declarations
+ * including keyword definitions specified as |CF_KEYWORDS|, |CF_GRAMMAR|
+ * for the grammar rules, |CF_CODE| for auxillary C code and finally
+ * |CF_END| at the end of the snippet.
+ *
+ * To create references between the snippets, it's possible to define
+ * multi-part rules by utilizing the |CF_ADDTO| macro which adds a new
+ * alternative to a multi-part rule.
+ *
+ * CLI commands are defined using a |CF_CLI| macro. Its parameters are:
+ * the list of keywords determining the command, the list of paramaters,
+ * help text for the parameters and help text for the command.
+ *
+ * Values of |enum| filter types can be defined using |CF_ENUM| with
+ * the following parameters: name of filter type, prefix common for all
+ * literals of this type, names of all the possible values.
+ */
+
 CF_HDR
 
 #include "nest/bird.h"