Re: [PATCH v8 01/18] drm/display: bridge_connector: Ensure last bridge determines EDID/modes detection capabilities
From: "Luca Ceresoli" <luca.ceresoli@bootlin.com>
Date: 2025-12-31 10:50:35
Also in:
dri-devel, imx, linux-rockchip, linux-samsung-soc, lkml
On Wed Dec 17, 2025 at 10:33 AM CET, Damon Ding wrote:
When multiple bridges are present, EDID detection capability (DRM_BRIDGE_OP_EDID) takes precedence over modes detection (DRM_BRIDGE_OP_MODES). To ensure the above two capabilities are determined by the last bridge in the chain, we handle three cases: Case 1: The later bridge declares only DRM_BRIDGE_OP_MODES - If the previous bridge declares DRM_BRIDGE_OP_EDID, set &drm_bridge_connector.bridge_edid to NULL and set &drm_bridge_connector.bridge_modes to the later bridge. - Ensure modes detection capability of the later bridge will not be ignored. Case 2: The later bridge declares only DRM_BRIDGE_OP_EDID - If the previous bridge declares DRM_BRIDGE_OP_MODES, set &drm_bridge_connector.bridge_modes to NULL and set &drm_bridge_connector.bridge_edid to the later bridge. - Although EDID detection capability has higher priority, this operation is for balance and makes sense. Case 3: the later bridge declares both of them - Assign later bridge as &drm_bridge_connector.bridge_edid and and &drm_bridge_connector.bridge_modes to this bridge. - Just leave transfer of these two capabilities as before. Signed-off-by: Damon Ding <redacted> Suggested-by: Dmitry Baryshkov <redacted> Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Luca Ceresoli <luca.ceresoli@bootlin.com> -- Luca Ceresoli, Bootlin Embedded Linux and Kernel engineering https://bootlin.com