[PATCH v8 01/18] drm/display: bridge_connector: Ensure last bridge determines EDID/modes detection capabilities

[Luca Ceresoli]

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 <damon.ding at rock-chips.com>
> Suggested-by: Dmitry Baryshkov <dmitry.baryshkov at oss.qualcomm.com>
> Tested-by: Marek Szyprowski <m.szyprowski at samsung.com>

Reviewed-by: Luca Ceresoli <luca.ceresoli at bootlin.com>

--
Luca Ceresoli, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com