Here's what's what in the firmware/ directory.
include/
lib/
These are the original structures and APIs used in the earliest
Chromebooks and continuing through 2014. It never had a version as such to
begin with, but we now refer to this implementation as "vboot1" or
"vboot version 1.0".
linktest/
stub/
These are stubs used to link the vboot1 libraries into host-side test
executables so we can run some tests on the build machine instead of a
Chromebook.
2lib/
In 2014 we began work on a new vboot API. The first step was just a
refactoring and renaming of the verification API. The public functions and
external headers that are exported for use by the Chrome OS firmware (or
anything else that wants to use vboot) live in here. The internal
structures and implementations go elsewhere.
lib20/
This is an early implementation of the public (2lib/) API. It is
binary-compatible with vboot1, so although the interface details are
different, any existing on-device structures or signatures created by the
vboot1 tools can be validated using this implementation.
This was deployed slightly before it was ready. That's not a problem,
thanks to the binary compatibility, but this directory will be abandoned
Real Soon Now, except for the product support branches.
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