[PATCH] drm/stm: ltdc: create blend mode property

Dario Binacchi dario.binacchi at amarulasolutions.com
Wed Oct 28 06:18:18 PDT 2026


After commit 860e748bddcc ("drm: ensure blend mode supported if pixel
format with alpha exposed") we get warnings at boot:

stm32-display 48010000.display-controller: [drm] [PLANE:37:plane-0] pixel format with alpha exposed but blend mode not setup. Please fix.

The LTDC blends the pixel formats with alpha by straight alpha, the
only mode implemented in the driver. Create the blend mode property
with DRM_MODE_BLEND_COVERAGE only.

Fixes: 860e748bddcc ("drm: ensure blend mode supported if pixel format with alpha exposed")
Signed-off-by: Dario Binacchi <dario.binacchi at amarulasolutions.com>

---

 drivers/gpu/drm/stm/ltdc.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/gpu/drm/stm/ltdc.c b/drivers/gpu/drm/stm/ltdc.c
index 5311e0b3e8dc..3b6e680c1c61 100644
--- a/drivers/gpu/drm/stm/ltdc.c
+++ b/drivers/gpu/drm/stm/ltdc.c
@@ -1642,6 +1642,7 @@ static struct drm_plane *ltdc_plane_create(struct drm_device *ddev,
 	drm_plane_helper_add(plane, &ltdc_plane_helper_funcs);
 
 	drm_plane_create_alpha_property(plane);
+	drm_plane_create_blend_mode_property(plane, BIT(DRM_MODE_BLEND_COVERAGE));
 
 	drm_dbg_driver(plane->dev, "plane:%d created\n", plane->base.id);
 
---
base-commit: 65ba8f34ec886ec72b2c07ddc8cf3d815c32869d
branch: stm32-ltdc-blend-mode

-- 
2.43.0




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