drm/tests: helpers: Allow for a custom device struct to be allocated

The current helper to allocate a DRM device doesn't allow for any
subclassing by drivers, which is going to be troublesome as we work on
getting some kunit testing on atomic modesetting code.

Let's use a similar pattern to the other allocation helpers by providing
the structure size and offset as arguments.

Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://lore.kernel.org/r/20221123-rpi-kunit-tests-v3-10-4615a663a84a@cerno.tech
Signed-off-by: Maxime Ripard <maxime@cerno.tech>

drivers/gpu/drm/tests/drm_client_modeset_test.c

@@ -63,7 +63,9 @@ static int drm_client_modeset_test_init(struct kunit *test)
 	priv->dev = drm_kunit_helper_alloc_device(test);
 	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, priv->dev);
 
-	priv->drm = drm_kunit_helper_alloc_drm_device(test, priv->dev, DRIVER_MODESET);
+	priv->drm = __drm_kunit_helper_alloc_drm_device(test, priv->dev,
+							sizeof(*priv->drm), 0,
+							DRIVER_MODESET);
 	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, priv->drm);
 
 	ret = drmm_connector_init(priv->drm, &priv->connector,

drivers/gpu/drm/tests/drm_kunit_helpers.c

@@ -11,10 +11,6 @@
 
 #define KUNIT_DEVICE_NAME	"drm-kunit-mock-device"
 
-struct kunit_dev {
-	struct drm_device base;
-};
-
 static const struct drm_mode_config_funcs drm_mode_config_funcs = {
 };
 
@@ -85,44 +81,26 @@ void drm_kunit_helper_free_device(struct kunit *test, struct device *dev)
 }
 EXPORT_SYMBOL_GPL(drm_kunit_helper_free_device);
 
-/**
- * drm_kunit_helper_alloc_drm_device - Allocates a mock DRM device for KUnit tests
- * @test: The test context object
- * @dev: The parent device object
- * @features: Mocked DRM device driver features
- *
- * This function creates a struct &drm_driver and will create a struct
- * &drm_device from @dev and that driver.
- *
- * @dev should be allocated using drm_kunit_helper_alloc_device().
- *
- * The driver is tied to the @test context and will get cleaned at the
- * end of the test. The drm_device is allocated through
- * devm_drm_dev_alloc() and will thus be freed through a device-managed
- * resource.
- *
- * Returns:
- * A pointer to the new drm_device, or an ERR_PTR() otherwise.
- */
 struct drm_device *
-drm_kunit_helper_alloc_drm_device(struct kunit *test, struct device *dev,
-				  u32 features)
+__drm_kunit_helper_alloc_drm_device(struct kunit *test, struct device *dev,
+				    size_t size, size_t offset,
+				    u32 features)
 {
-	struct kunit_dev *kdev;
 	struct drm_device *drm;
 	struct drm_driver *driver;
+	void *container;
 	int ret;
 
 	driver = kunit_kzalloc(test, sizeof(*driver), GFP_KERNEL);
 	if (!driver)
 		return ERR_PTR(-ENOMEM);
 
 	driver->driver_features = features;
-	kdev = devm_drm_dev_alloc(dev, driver, struct kunit_dev, base);
-	if (IS_ERR(kdev))
-		return ERR_CAST(kdev);
+	container = __devm_drm_dev_alloc(dev, driver, size, offset);
+	if (IS_ERR(container))
+		return ERR_CAST(container);
 
-	drm = &kdev->base;
+	drm = container + offset;
 	drm->mode_config.funcs = &drm_mode_config_funcs;
 
 	ret = drmm_mode_config_init(drm);
@@ -131,7 +109,7 @@ drm_kunit_helper_alloc_drm_device(struct kunit *test, struct device *dev,
 
 	return drm;
 }
-EXPORT_SYMBOL_GPL(drm_kunit_helper_alloc_drm_device);
+EXPORT_SYMBOL_GPL(__drm_kunit_helper_alloc_drm_device);
 
 MODULE_AUTHOR("Maxime Ripard <maxime@cerno.tech>");
 MODULE_LICENSE("GPL");

drivers/gpu/drm/tests/drm_modes_test.c

@@ -26,8 +26,9 @@ static int drm_test_modes_init(struct kunit *test)
 	priv->dev = drm_kunit_helper_alloc_device(test);
 	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, priv->dev);
 
-	priv->drm = drm_kunit_helper_alloc_drm_device(test, priv->dev,
-						      DRIVER_MODESET);
+	priv->drm = __drm_kunit_helper_alloc_drm_device(test, priv->dev,
+							sizeof(*priv->drm), 0,
+							DRIVER_MODESET);
 	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, priv->drm);
 
 	test->priv = priv;

drivers/gpu/drm/tests/drm_probe_helper_test.c

@@ -43,8 +43,9 @@ static int drm_probe_helper_test_init(struct kunit *test)
 	priv->dev = drm_kunit_helper_alloc_device(test);
 	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, priv->dev);
 
-	priv->drm = drm_kunit_helper_alloc_drm_device(test, priv->dev,
-						      DRIVER_MODESET | DRIVER_ATOMIC);
+	priv->drm = __drm_kunit_helper_alloc_drm_device(test, priv->dev,
+							sizeof(*priv->drm), 0,
+							DRIVER_MODESET | DRIVER_ATOMIC);
 	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, priv->drm);
 
 	connector = &priv->connector;

include/drm/drm_kunit_helpers.h

@@ -10,7 +10,35 @@ struct device *drm_kunit_helper_alloc_device(struct kunit *test);
 void drm_kunit_helper_free_device(struct kunit *test, struct device *dev);
 
 struct drm_device *
-drm_kunit_helper_alloc_drm_device(struct kunit *test, struct device *dev,
-				  u32 features);
+__drm_kunit_helper_alloc_drm_device(struct kunit *test, struct device *dev,
+				    size_t size, size_t offset,
+				    u32 features);
+
+/**
+ * drm_kunit_helper_alloc_drm_device - Allocates a mock DRM device for KUnit tests
+ * @_test: The test context object
+ * @_dev: The parent device object
+ * @_type: the type of the struct which contains struct &drm_device
+ * @_member: the name of the &drm_device within @_type.
+ * @_features: Mocked DRM device driver features
+ *
+ * This function creates a struct &drm_driver and will create a struct
+ * &drm_device from @_dev and that driver.
+ *
+ * @_dev should be allocated using drm_kunit_helper_alloc_device().
+ *
+ * The driver is tied to the @_test context and will get cleaned at the
+ * end of the test. The drm_device is allocated through
+ * devm_drm_dev_alloc() and will thus be freed through a device-managed
+ * resource.
+ *
+ * Returns:
+ * A pointer to the new drm_device, or an ERR_PTR() otherwise.
+ */
+#define drm_kunit_helper_alloc_drm_device(_test, _dev, _type, _member, _feat)	\
+	((_type *)__drm_kunit_helper_alloc_drm_device(_test, _dev,		\
+						      sizeof(_type),		\
+						      offsetof(_type, _member),	\
+						      _feat))
 
 #endif // DRM_KUNIT_HELPERS_H_