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authordavidgow@google.com <davidgow@google.com>2023-12-15 15:39:08 +0800
committerShuah Khan <skhan@linuxfoundation.org>2023-12-18 13:28:08 -0700
commitd03c720e03bd9bf0b784d80b5d3ede7e2daf3b6e (patch)
tree283ce85c21b45fd4ba3782367727f85afdc6dc4a /Documentation/dev-tools
parente9f0e21ceb65ea5e450ede7c9b9a5bfc90a403ae (diff)
kunit: Add APIs for managing devices
Tests for drivers often require a struct device to pass to other functions. While it's possible to create these with root_device_register(), or to use something like a platform device, this is both a misuse of those APIs, and can be difficult to clean up after, for example, a failed assertion. Add some KUnit-specific functions for registering and unregistering a struct device: - kunit_device_register() - kunit_device_register_with_driver() - kunit_device_unregister() These helpers allocate a on a 'kunit' bus which will either probe the driver passed in (kunit_device_register_with_driver), or will create a stub driver (kunit_device_register) which is cleaned up on test shutdown. Devices are automatically unregistered on test shutdown, but can be manually unregistered earlier with kunit_device_unregister() in order to, for example, test device release code. Reviewed-by: Matti Vaittinen <mazziesaccount@gmail.com> Reviewed-by: Maxime Ripard <mripard@kernel.org> Signed-off-by: David Gow <davidgow@google.com> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
Diffstat (limited to 'Documentation/dev-tools')
-rw-r--r--Documentation/dev-tools/kunit/api/resource.rst9
-rw-r--r--Documentation/dev-tools/kunit/usage.rst50
2 files changed, 59 insertions, 0 deletions
diff --git a/Documentation/dev-tools/kunit/api/resource.rst b/Documentation/dev-tools/kunit/api/resource.rst
index 0a94f831259e..ec6002a6b0db 100644
--- a/Documentation/dev-tools/kunit/api/resource.rst
+++ b/Documentation/dev-tools/kunit/api/resource.rst
@@ -11,3 +11,12 @@ state on a per-test basis, register custom cleanup actions, and more.
.. kernel-doc:: include/kunit/resource.h
:internal:
+
+Managed Devices
+---------------
+
+Functions for using KUnit-managed struct device and struct device_driver.
+Include ``kunit/device.h`` to use these.
+
+.. kernel-doc:: include/kunit/device.h
+ :internal:
diff --git a/Documentation/dev-tools/kunit/usage.rst b/Documentation/dev-tools/kunit/usage.rst
index 9db12e91668e..53c6f7dc8a42 100644
--- a/Documentation/dev-tools/kunit/usage.rst
+++ b/Documentation/dev-tools/kunit/usage.rst
@@ -797,3 +797,53 @@ structures as shown below:
KUnit is not enabled, or if no test is running in the current task, it will do
nothing. This compiles down to either a no-op or a static key check, so will
have a negligible performance impact when no test is running.
+
+Managing Fake Devices and Drivers
+---------------------------------
+
+When testing drivers or code which interacts with drivers, many functions will
+require a ``struct device`` or ``struct device_driver``. In many cases, setting
+up a real device is not required to test any given function, so a fake device
+can be used instead.
+
+KUnit provides helper functions to create and manage these fake devices, which
+are internally of type ``struct kunit_device``, and are attached to a special
+``kunit_bus``. These devices support managed device resources (devres), as
+described in Documentation/driver-api/driver-model/devres.rst
+
+To create a KUnit-managed ``struct device_driver``, use ``kunit_driver_create()``,
+which will create a driver with the given name, on the ``kunit_bus``. This driver
+will automatically be destroyed when the corresponding test finishes, but can also
+be manually destroyed with ``driver_unregister()``.
+
+To create a fake device, use the ``kunit_device_register()``, which will create
+and register a device, using a new KUnit-managed driver created with ``kunit_driver_create()``.
+To provide a specific, non-KUnit-managed driver, use ``kunit_device_register_with_driver()``
+instead. Like with managed drivers, KUnit-managed fake devices are automatically
+cleaned up when the test finishes, but can be manually cleaned up early with
+``kunit_device_unregister()``.
+
+The KUnit devices should be used in preference to ``root_device_register()``, and
+instead of ``platform_device_register()`` in cases where the device is not otherwise
+a platform device.
+
+For example:
+
+.. code-block:: c
+
+ #include <kunit/device.h>
+
+ static void test_my_device(struct kunit *test)
+ {
+ struct device *fake_device;
+ const char *dev_managed_string;
+
+ // Create a fake device.
+ fake_device = kunit_device_register(test, "my_device");
+ KUNIT_ASSERT_NOT_ERR_OR_NULL(test, fake_device)
+
+ // Pass it to functions which need a device.
+ dev_managed_string = devm_kstrdup(fake_device, "Hello, World!");
+
+ // Everything is cleaned up automatically when the test ends.
+ } \ No newline at end of file