Documentation: Add debugfs docs with run after boot

Expand the documentation on the KUnit debugfs filesystem on the
run_manual.rst page.

Add section describing how to access results using debugfs.

Add section describing how to run tests after boot using debugfs.

Reviewed-by: David Gow <davidgow@google.com>
Signed-off-by: Rae Moar <rmoar@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

diff --git a/Documentation/dev-tools/kunit/run_manual.rst b/Documentation/dev-tools/kunit/run_manual.rst
index e7b46421f247e16a16a972f8a6fbfe4bc5296706..699d92885075082a06c9de0e06a1a33dcdfbb440 100644 (file)
--- a/Documentation/dev-tools/kunit/run_manual.rst
+++ b/Documentation/dev-tools/kunit/run_manual.rst
@@ -49,9 +49,52 @@ loaded.
 
 The results will appear in TAP format in ``dmesg``.
 
+debugfs
+=======
+
+KUnit can be accessed from userspace via the debugfs filesystem (See more
+information about debugfs at Documentation/filesystems/debugfs.rst).
+
+If ``CONFIG_KUNIT_DEBUGFS`` is enabled, the KUnit debugfs filesystem is
+mounted at /sys/kernel/debug/kunit. You can use this filesystem to perform
+the following actions.
+
+Retrieve Test Results
+=====================
+
+You can use debugfs to retrieve KUnit test results. The test results are
+accessible from the debugfs filesystem in the following read-only file:
+
+.. code-block :: bash
+
+       /sys/kernel/debug/kunit/<test_suite>/results
+
+The test results are printed in a KTAP document. Note this document is separate
+to the kernel log and thus, may have different test suite numbering.
+
+Run Tests After Kernel Has Booted
+=================================
+
+You can use the debugfs filesystem to trigger built-in tests to run after
+boot. To run the test suite, you can use the following command to write to
+the ``/sys/kernel/debug/kunit/<test_suite>/run`` file:
+
+.. code-block :: bash
+
+       echo "any string" > /sys/kernel/debugfs/kunit/<test_suite>/run
+
+As a result, the test suite runs and the results are printed to the kernel
+log.
+
+However, this feature is not available with KUnit suites that use init data,
+because init data may have been discarded after the kernel boots. KUnit
+suites that use init data should be defined using the
+kunit_test_init_section_suites() macro.
+
+Also, you cannot use this feature to run tests concurrently. Instead a test
+will wait to run until other tests have completed or failed.
+
 .. note ::
 
-       If ``CONFIG_KUNIT_DEBUGFS`` is enabled, KUnit test results will
-       be accessible from the ``debugfs`` filesystem (if mounted).
-       They will be in ``/sys/kernel/debug/kunit/<test_suite>/results``, in
-       TAP format.
+       For test authors, to use this feature, tests will need to correctly initialise
+       and/or clean up any data, so the test runs correctly a second time.