Update README.md.

1 files changed, 34 insertions, 3 deletions

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@@ -5,6 +5,37 @@ Release engineering tree for the Cryptech code for the Novena PVT-1,
 initially targetted at what we need to package for IETF 93 in Praha.
 
 General idea is to build two binary packages, one with the bitstream
-for the FPGA, one for software cross-compiled for the Novena.  Might
-want a third package just as a meta package to pull the first two in
-via dependencies.
+for the FPGA, one for software cross-compiled for the Novena.  As a
+convenience, there's also a meta-package which just pulls in the first
+two as dependencies.
+
+The current build setup is somewhat specific to the Novena (in
+particular, the use of the Debian package system), but the general
+outline will likely be reusable for other platforms in the future.
+
+Overall structure of the current setup:
+
+* The top-level Makefile controls the overall build process.  It does
+  _not_ run make directly on any of its subdirectories, instead it
+  invokes the Debian package building tools with the right settings.
+
+* Each of the three packages generated has its own Makefile and
+  debian/ directory.  These Makefiles are intended to work with the
+  Debian package building tools, and do not necessarily do anything
+  useful if used in any other context.
+
+* Building the software package requires a cross-compiler, see
+  [the Debian cross compilation tools page][CrossToolchains].
+
+* Building the firmware package requires
+  [the XiLinx tools][XiLinxTools].
+
+* You'll also need the usual Debian package building tools, as well as
+  Python and the python-yaml library.
+
+* The software and Verilog repositories are spliced into this one
+  using git's submodule mechanism.  The top-level Makefile attempts to
+  automate all of the submodule voodoo needed for normal builds.
+
+[CrossToolchains]:	https://wiki.debian.org/CrossToolchains
+[XiLinxTools]:		http://www.xilinx.com/support/download/index.html/content/xilinx/en/downloadNav/design-tools.html