drm/tests: Add helper to create mock plane

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, primary plane. By
default, it will create a linear XRGB8888 plane, using the default
helpers.
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-v7-3-8f4af575fce2@kernel.org

drivers/gpu/drm/tests/drm_kunit_helpers.c

@@ -3,6 +3,7 @@
 #include <drm/drm_atomic.h>
 #include <drm/drm_atomic_helper.h>
 #include <drm/drm_drv.h>
+#include <drm/drm_fourcc.h>
 #include <drm/drm_kunit_helpers.h>
 #include <drm/drm_managed.h>
 
@@ -164,5 +165,89 @@ drm_kunit_helper_atomic_state_alloc(struct kunit *test,
 }
 EXPORT_SYMBOL_GPL(drm_kunit_helper_atomic_state_alloc);
 
+static const uint32_t default_plane_formats[] = {
+	DRM_FORMAT_XRGB8888,
+};
+
+static const uint64_t default_plane_modifiers[] = {
+	DRM_FORMAT_MOD_LINEAR,
+	DRM_FORMAT_MOD_INVALID
+};
+
+static const struct drm_plane_helper_funcs default_plane_helper_funcs = {
+};
+
+static const struct drm_plane_funcs default_plane_funcs = {
+	.atomic_destroy_state	= drm_atomic_helper_plane_destroy_state,
+	.atomic_duplicate_state	= drm_atomic_helper_plane_duplicate_state,
+	.reset			= drm_atomic_helper_plane_reset,
+};
+
+/**
+ * drm_kunit_helper_create_primary_plane - Creates a mock primary plane for a KUnit test
+ * @test: The test context object
+ * @drm: The device to alloc the plane for
+ * @funcs: Callbacks for the new plane. Optional.
+ * @helper_funcs: Helpers callbacks for the new plane. Optional.
+ * @formats: array of supported formats (DRM_FORMAT\_\*). Optional.
+ * @num_formats: number of elements in @formats
+ * @modifiers: array of struct drm_format modifiers terminated by
+ *             DRM_FORMAT_MOD_INVALID. Optional.
+ *
+ * This allocates and initializes a mock struct &drm_plane 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. @formats will
+ * default to XRGB8888 only. @modifiers will default to a linear
+ * modifier only.
+ *
+ * Returns:
+ * A pointer to the new plane, or an ERR_PTR() otherwise.
+ */
+struct drm_plane *
+drm_kunit_helper_create_primary_plane(struct kunit *test,
+				      struct drm_device *drm,
+				      const struct drm_plane_funcs *funcs,
+				      const struct drm_plane_helper_funcs *helper_funcs,
+				      const uint32_t *formats,
+				      unsigned int num_formats,
+				      const uint64_t *modifiers)
+{
+	struct drm_plane *plane;
+
+	if (!funcs)
+		funcs = &default_plane_funcs;
+
+	if (!helper_funcs)
+		helper_funcs = &default_plane_helper_funcs;
+
+	if (!formats || !num_formats) {
+		formats = default_plane_formats;
+		num_formats = ARRAY_SIZE(default_plane_formats);
+	}
+
+	if (!modifiers)
+		modifiers = default_plane_modifiers;
+
+	plane = __drmm_universal_plane_alloc(drm,
+					     sizeof(struct drm_plane), 0,
+					     0,
+					     funcs,
+					     formats,
+					     num_formats,
+					     default_plane_modifiers,
+					     DRM_PLANE_TYPE_PRIMARY,
+					     NULL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, plane);
+
+	drm_plane_helper_add(plane, helper_funcs);
+
+	return plane;
+}
+EXPORT_SYMBOL_GPL(drm_kunit_helper_create_primary_plane);
+
 MODULE_AUTHOR("Maxime Ripard <maxime@cerno.tech>");
 MODULE_LICENSE("GPL");

include/drm/drm_kunit_helpers.h

@@ -10,6 +10,8 @@
 #include <kunit/test.h>
 
 struct drm_device;
+struct drm_plane_funcs;
+struct drm_plane_helper_funcs;
 struct kunit;
 
 struct device *drm_kunit_helper_alloc_device(struct kunit *test);
@@ -99,4 +101,13 @@ drm_kunit_helper_atomic_state_alloc(struct kunit *test,
 				    struct drm_device *drm,
 				    struct drm_modeset_acquire_ctx *ctx);
 
+struct drm_plane *
+drm_kunit_helper_create_primary_plane(struct kunit *test,
+				      struct drm_device *drm,
+				      const struct drm_plane_funcs *funcs,
+				      const struct drm_plane_helper_funcs *helper_funcs,
+				      const uint32_t *formats,
+				      unsigned int num_formats,
+				      const uint64_t *modifiers);
+
 #endif // DRM_KUNIT_HELPERS_H_