drm/tests: Add helper to create mock crtc

We're going to need a full-blown, functional, KMS device to test more
components of the atomic modesetting infrastructure.

Let's add a new helper to create a dumb, mocked, CRTC. By default it
will create a CRTC relying only on the default helpers, but drivers are
free to deviate from that.
Reviewed-by: Maíra Canal <mcanal@igalia.com>
Signed-off-by: Maxime Ripard <mripard@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240222-kms-hdmi-connector-state-v7-4-8f4af575fce2@kernel.org

drivers/gpu/drm/tests/drm_kunit_helpers.c

@@ -249,5 +249,67 @@ drm_kunit_helper_create_primary_plane(struct kunit *test,
 }
 EXPORT_SYMBOL_GPL(drm_kunit_helper_create_primary_plane);
 
+static const struct drm_crtc_helper_funcs default_crtc_helper_funcs = {
+};
+
+static const struct drm_crtc_funcs default_crtc_funcs = {
+	.atomic_destroy_state   = drm_atomic_helper_crtc_destroy_state,
+	.atomic_duplicate_state = drm_atomic_helper_crtc_duplicate_state,
+	.reset                  = drm_atomic_helper_crtc_reset,
+};
+
+/**
+ * drm_kunit_helper_create_crtc - Creates a mock CRTC for a KUnit test
+ * @test: The test context object
+ * @drm: The device to alloc the plane for
+ * @primary: Primary plane for CRTC
+ * @cursor: Cursor plane for CRTC. Optional.
+ * @funcs: Callbacks for the new plane. Optional.
+ * @helper_funcs: Helpers callbacks for the new plane. Optional.
+ *
+ * This allocates and initializes a mock struct &drm_crtc meant to be
+ * part of a mock device for a KUnit test.
+ *
+ * Resources will be cleaned up automatically.
+ *
+ * @funcs will default to the default helpers implementations.
+ * @helper_funcs will default to an empty implementation.
+ *
+ * Returns:
+ * A pointer to the new CRTC, or an ERR_PTR() otherwise.
+ */
+struct drm_crtc *
+drm_kunit_helper_create_crtc(struct kunit *test,
+			     struct drm_device *drm,
+			     struct drm_plane *primary,
+			     struct drm_plane *cursor,
+			     const struct drm_crtc_funcs *funcs,
+			     const struct drm_crtc_helper_funcs *helper_funcs)
+{
+	struct drm_crtc *crtc;
+	int ret;
+
+	if (!funcs)
+		funcs = &default_crtc_funcs;
+
+	if (!helper_funcs)
+		helper_funcs = &default_crtc_helper_funcs;
+
+	crtc = drmm_kzalloc(drm, sizeof(*crtc), GFP_KERNEL);
+	KUNIT_ASSERT_NOT_NULL(test, crtc);
+
+	ret = drmm_crtc_init_with_planes(drm, crtc,
+					 primary,
+					 cursor,
+					 funcs,
+					 NULL);
+	KUNIT_ASSERT_EQ(test, ret, 0);
+
+	drm_crtc_helper_add(crtc, helper_funcs);
+
+	return crtc;
+}
+EXPORT_SYMBOL_GPL(drm_kunit_helper_create_crtc);
+
 MODULE_AUTHOR("Maxime Ripard <maxime@cerno.tech>");
 MODULE_LICENSE("GPL");

include/drm/drm_kunit_helpers.h

@@ -9,6 +9,8 @@
 
 #include <kunit/test.h>
 
+struct drm_crtc_funcs;
+struct drm_crtc_helper_funcs;
 struct drm_device;
 struct drm_plane_funcs;
 struct drm_plane_helper_funcs;
@@ -110,4 +112,12 @@ drm_kunit_helper_create_primary_plane(struct kunit *test,
 				      unsigned int num_formats,
 				      const uint64_t *modifiers);
 
+struct drm_crtc *
+drm_kunit_helper_create_crtc(struct kunit *test,
+			     struct drm_device *drm,
+			     struct drm_plane *primary,
+			     struct drm_plane *cursor,
+			     const struct drm_crtc_funcs *funcs,
+			     const struct drm_crtc_helper_funcs *helper_funcs);
+
 #endif // DRM_KUNIT_HELPERS_H_