[PATCH v6 15/15] drm/vkms: Add driver-specific plane property for testing

[Maxime Ripard <mripard@kernel.org>]

The DRM_MODE_ATOMIC_RESET flag allows userspace to reset all object
states to their defaults before applying new property values. Testing
that this mechanism works correctly requires a property that the test
can set to a non-default value and then verify is properly reset.

Using a standard property for this is problematic: compositors like
Mutter enumerate and track all known properties, making it difficult
to isolate the reset behavior from the compositor's own property
management.

Add a "vkms-test-do-not-use-in-prod" range property to vkms planes.
The property is stored in vkms_plane_state, duplicated across state
copies, and initialized from its registered default in
atomic_create_state via drm_object_property_get_default_value().

Reviewed-by: Daniel Stone <daniels@collabora.com>
Signed-off-by: Maxime Ripard <mripard@kernel.org>
---
 drivers/gpu/drm/vkms/vkms_drv.h   |  3 ++
 drivers/gpu/drm/vkms/vkms_plane.c | 61 +++++++++++++++++++++++++++++++++++++--
 2 files changed, 62 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/vkms/vkms_drv.h b/drivers/gpu/drm/vkms/vkms_drv.h
index dea6cad3f1b9..384616095b45 100644
--- a/drivers/gpu/drm/vkms/vkms_drv.h
+++ b/drivers/gpu/drm/vkms/vkms_drv.h
@@ -147,4 +147,5 @@ struct conversion_matrix {
  *		     struct vkms_plane_state must ensure that this pointer is valid
  * @conversion_matrix: matrix used for yuv formats to convert to rgb
+ * @vkms_test_do_not_use_value: driver-specific property for testing only
  */
 struct vkms_plane_state {
@@ -153,8 +154,10 @@ struct vkms_plane_state {
 	pixel_read_line_t pixel_read_line;
 	struct conversion_matrix conversion_matrix;
+	unsigned int vkms_test_do_not_use_value;
 };
 
 struct vkms_plane {
 	struct drm_plane base;
+	struct drm_property *vkms_test_do_not_use_property;
 };
 
diff --git a/drivers/gpu/drm/vkms/vkms_plane.c b/drivers/gpu/drm/vkms/vkms_plane.c
index fd3d34dcf0fe..0ebc131c2788 100644
--- a/drivers/gpu/drm/vkms/vkms_plane.c
+++ b/drivers/gpu/drm/vkms/vkms_plane.c
@@ -12,8 +12,12 @@
 #include <drm/drm_gem_framebuffer_helper.h>
 #include <drm/drm_print.h>
+#include <drm/drm_property.h>
 
 #include "vkms_drv.h"
 #include "vkms_formats.h"
 
+#define to_vkms_plane(target) \
+	container_of_const(target, struct vkms_plane, base)
+
 static const u32 vkms_formats[] = {
 	DRM_FORMAT_ARGB8888,
@@ -55,4 +59,5 @@ static struct drm_plane_state *
 vkms_plane_duplicate_state(struct drm_plane *plane)
 {
+	struct vkms_plane_state *old_state = to_vkms_plane_state(plane->state);
 	struct vkms_plane_state *vkms_state;
 
@@ -61,4 +66,6 @@ vkms_plane_duplicate_state(struct drm_plane *plane)
 		return NULL;
 
+	vkms_state->vkms_test_do_not_use_value = old_state->vkms_test_do_not_use_value;
+
 	__drm_gem_duplicate_shadow_plane_state(plane, &vkms_state->base);
 
@@ -86,5 +93,7 @@ static void vkms_plane_destroy_state(struct drm_plane *plane,
 static struct drm_plane_state *vkms_plane_create_state(struct drm_plane *plane)
 {
+	struct vkms_plane *vkms_plane = to_vkms_plane(plane);
 	struct vkms_plane_state *vkms_state;
+	u64 val;
 
 	vkms_state = kzalloc_obj(*vkms_state);
@@ -96,12 +105,51 @@ static struct drm_plane_state *vkms_plane_create_state(struct drm_plane *plane)
 	__drm_gem_shadow_plane_state_init(plane, &vkms_state->base);
 
+	if (!drm_object_property_get_default_value(&plane->base,
+						   vkms_plane->vkms_test_do_not_use_property,
+						   &val))
+		vkms_state->vkms_test_do_not_use_value = val;
+
 	return &(&vkms_state->base)->base;
 }
 
+static int vkms_plane_atomic_set_property(struct drm_plane *plane,
+					  struct drm_plane_state *state,
+					  struct drm_property *property,
+					  uint64_t val)
+{
+	struct vkms_plane *vkms_plane = to_vkms_plane(plane);
+	struct vkms_plane_state *vkms_state = to_vkms_plane_state(state);
+
+	if (property == vkms_plane->vkms_test_do_not_use_property) {
+		vkms_state->vkms_test_do_not_use_value = val;
+		return 0;
+	}
+
+	return -EINVAL;
+}
+
+static int vkms_plane_atomic_get_property(struct drm_plane *plane,
+					  const struct drm_plane_state *state,
+					  struct drm_property *property,
+					  uint64_t *val)
+{
+	const struct vkms_plane_state *vkms_state = to_vkms_plane_state(state);
+	const struct vkms_plane *vkms_plane = to_vkms_plane(plane);
+
+	if (property == vkms_plane->vkms_test_do_not_use_property) {
+		*val = vkms_state->vkms_test_do_not_use_value;
+		return 0;
+	}
+
+	return -EINVAL;
+}
+
 static const struct drm_plane_funcs vkms_plane_funcs = {
 	.update_plane		= drm_atomic_helper_update_plane,
 	.disable_plane		= drm_atomic_helper_disable_plane,
-	.atomic_create_state = vkms_plane_create_state,
-	.atomic_duplicate_state = vkms_plane_duplicate_state,
+	.atomic_set_property	= vkms_plane_atomic_set_property,
+	.atomic_get_property	= vkms_plane_atomic_get_property,
+	.atomic_create_state	= vkms_plane_create_state,
+	.atomic_duplicate_state	= vkms_plane_duplicate_state,
 	.atomic_destroy_state	= vkms_plane_destroy_state,
 };
@@ -284,4 +332,13 @@ struct vkms_plane *vkms_plane_init(struct vkms_device *vkmsdev,
 					  DRM_COLOR_YCBCR_FULL_RANGE);
 
+	plane->vkms_test_do_not_use_property =
+		drm_property_create_range(dev, 0,
+					  "vkms-test-do-not-use-in-prod",
+					  0, U32_MAX);
+	if (plane->vkms_test_do_not_use_property)
+		drm_object_attach_property(&plane->base.base,
+					   plane->vkms_test_do_not_use_property,
+					   0);
+
 	if (vkms_config_plane_get_default_pipeline(plane_cfg))
 		vkms_initialize_colorops(&plane->base);

-- 
2.55.0