kunit: update documentation to describe module-based build

Documentation should describe how to build kunit and tests as
modules.

Co-developed-by: Knut Omang <[email protected]>
Signed-off-by: Knut Omang <[email protected]>
Signed-off-by: Alan Maguire <[email protected]>
Reviewed-by: Stephen Boyd <[email protected]>
Reviewed-by: Brendan Higgins <[email protected]>
Signed-off-by: Shuah Khan <[email protected]>

Author: alan-maguire

Documentation/dev-tools/kunit/faq.rst

@@ -29,7 +29,8 @@ Yes, well, mostly.
 
 For the most part, the KUnit core framework (what you use to write the tests)
 can compile to any architecture; it compiles like just another part of the
-kernel and runs when the kernel boots. However, there is some infrastructure,
+kernel and runs when the kernel boots, or when built as a module, when the
+module is loaded.  However, there is some infrastructure,
 like the KUnit Wrapper (``tools/testing/kunit/kunit.py``) that does not support
 other architectures.
 

Documentation/dev-tools/kunit/index.rst

@@ -49,6 +49,9 @@ to a standalone program that can be run like any other program directly inside
 of a host operating system; to be clear, it does not require any virtualization
 support; it is just a regular program.
 
+Alternatively, kunit and kunit tests can be built as modules and tests will
+run when the test module is loaded.
+
 KUnit is fast. Excluding build time, from invocation to completion KUnit can run
 several dozen tests in only 10 to 20 seconds; this might not sound like a big
 deal to some people, but having such fast and easy to run tests fundamentally

Documentation/dev-tools/kunit/usage.rst

@@ -539,6 +539,22 @@ Interspersed in the kernel logs you might see the following:
 
 Congratulations, you just ran a KUnit test on the x86 architecture!
 
+In a similar manner, kunit and kunit tests can also be built as modules,
+so if you wanted to run tests in this way you might add the following config
+options to your ``.config``:
+
+.. code-block:: none
+
+	CONFIG_KUNIT=m
+	CONFIG_KUNIT_EXAMPLE_TEST=m
+
+Once the kernel is built and installed, a simple
+
+.. code-block:: bash
+	modprobe example-test
+
+...will run the tests.
+
 Writing new tests for other architectures
 -----------------------------------------