[RFC PATCH 2/3] drm/atomic-helper: add REQUIRE_MATCHING_FB flag

[Stefan Agner <stefan@agner.ch>]

Add flag which checks that the framebuffer size matches the plane size
exactly. This is useful for display controller which can't handle
framebuffers other than the plane/CRTC size.

Signed-off-by: Stefan Agner <stefan@agner.ch>
---
 drivers/gpu/drm/drm_atomic_helper.c               | 7 +++++++
 drivers/gpu/drm/selftests/test-drm_plane_helper.c | 9 +++++++++
 include/drm/drm_atomic_helper.h                   | 1 +
 3 files changed, 17 insertions(+)

diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index 755572a37f3f..8bc7f8c2e566 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -802,6 +802,7 @@ int drm_atomic_helper_check_plane_state(struct drm_plane_state *plane_state,
 	int hscale, vscale;
 	bool can_position = flags & DRM_PLANE_CAN_POSITION;
 	bool can_update_disabled = flags & DRM_PLANE_CAN_UPDATE_DISABLED;
+	bool require_matching_fb = flags & DRM_PLANE_REQUIRE_MATCHING_FB;
 
 	WARN_ON(plane_state->crtc && plane_state->crtc != crtc_state->crtc);
 
@@ -860,6 +861,12 @@ int drm_atomic_helper_check_plane_state(struct drm_plane_state *plane_state,
 		return -EINVAL;
 	}
 
+	if (require_matching_fb && (drm_rect_width(src) != fb->width ||
+	    drm_rect_height(src) != fb->height)) {
+		DRM_DEBUG_KMS("Framebuffer size must match plane size.\n");
+		return -EINVAL;
+	}
+
 	return 0;
 }
 EXPORT_SYMBOL(drm_atomic_helper_check_plane_state);
diff --git a/drivers/gpu/drm/selftests/test-drm_plane_helper.c b/drivers/gpu/drm/selftests/test-drm_plane_helper.c
index 01e95b2d572f..2c81bbef830e 100644
--- a/drivers/gpu/drm/selftests/test-drm_plane_helper.c
+++ b/drivers/gpu/drm/selftests/test-drm_plane_helper.c
@@ -139,6 +139,15 @@ int igt_check_plane_state(void *ignored)
 	FAIL_ON(!check_src_eq(&plane_state, 0, 0, 1023 << 16, 767 << 16));
 	FAIL_ON(!check_crtc_eq(&plane_state, 0, 0, 1023, 767));
 
+	/* Check whether requiring same size framebuffer works correctly. */
+	set_src(&plane_state, 0, 0, 1024 << 16, 768 << 16);
+	set_crtc(&plane_state, 0, 0, 1024, 768);
+	ret = drm_atomic_helper_check_plane_state(&plane_state, &crtc_state,
+						  DRM_PLANE_HELPER_NO_SCALING,
+						  DRM_PLANE_HELPER_NO_SCALING,
+						  DRM_PLANE_REQUIRE_MATCHING_FB);
+	FAIL(!ret, "Should not be able to use different size framebuffer with REQUIRE_MATCHING_FB\n");
+
 	/* Simple scaling tests. */
 	set_src(&plane_state, 0, 0, 512 << 16, 384 << 16);
 	set_crtc(&plane_state, 0, 0, 1024, 768);
diff --git a/include/drm/drm_atomic_helper.h b/include/drm/drm_atomic_helper.h
index bb9957b4f91b..244b730e84d3 100644
--- a/include/drm/drm_atomic_helper.h
+++ b/include/drm/drm_atomic_helper.h
@@ -43,6 +43,7 @@ int drm_atomic_helper_check_modeset(struct drm_device *dev,
 
 #define DRM_PLANE_CAN_POSITION				BIT(0)
 #define DRM_PLANE_CAN_UPDATE_DISABLED			BIT(1)
+#define DRM_PLANE_REQUIRE_MATCHING_FB			BIT(2)
 
 int drm_atomic_helper_check_plane_state(struct drm_plane_state *plane_state,
 					const struct drm_crtc_state *crtc_state,
-- 
2.28.0

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