Added developer documentation.

diff --git a/virt-df/README b/virt-df/README
index 0623030..c3ba4fe 100644 (file)
--- a/virt-df/README
+++ b/virt-df/README
@@ -1,2 +1,68 @@
+$Id$
+
+For user documentation:
+
 Please see the manual page (virt-df.pod or virt-df.txt in this
-directory).
\ No newline at end of file
+directory).
+
+Developer documentation
+----------------------------------------------------------------------
+
+This program has suddenly become rather large and confusing.
+Hopefully this documentation should go some way towards explaining
+what is going on inside the source.
+
+The main program consists of two modules:
+
+ - virt_df.ml / virt_df.mli (module name: Virt_df)
+
+   This has evolved into a library of miscellaneous functions
+   and values which are included throughout the rest of the
+   program.  If you see an unexplained function then it's
+   likely that it is defined in here.
+
+   Start by reading virt_df.mli which contains the full types
+   and plenty of documentation.
+
+ - virt_df_main.ml
+
+   This is the program.  It reads the command line arguments,
+   loads the domain descriptions, calls out to the plug-ins
+   to probe for disks / partitions / filesystems / etc., and
+   finally prints the results.
+
+   The file consists of basically one large program that
+   does all of the above in sequence.
+
+Everything else in this directory is a plug-in specialized for probing
+a particular filesystem, partition scheme or type of LVM.  The
+plug-ins at time of writing are:
+
+ - virt_df_ext2.ml / virt_df_ext2.mli
+
+   EXT2/3/4 plug-in.
+
+ - virt_df_linux_swap.ml / virt_df_linux_swap.mli
+
+   Linux swap (new style).
+
+ - virt_df_mbr.ml / virt_df_mbr.mli
+
+   Master Boot Record (MS-DOS) disk partitioning.
+
+ - virt_df_lvm2*
+
+   LVM2 parsing, which is by far the most complex plug-in.
+   It consists of:
+
+   - virt_df_lvm2.ml
+   - virt_df_lvm2.mli
+     LVM2 probing, PV detection.
+
+   - virt_df_lvm2_parser.mly
+   - virt_df_lvm2_lexer.mll
+     Scanner/parser for parsing LVM2 metadata definitions.
+
+   - virt_df_lvm2_metadata.ml
+   - virt_df_lvm2_metadata.mli
+     AST for LVM2 metadata definitions.