Hello Damon,
On Tue Oct 21, 2025 at 4:31 AM CEST, 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 <[email protected]>
> Suggested-by: Dmitry Baryshkov <[email protected]>
> Tested-by: Marek Szyprowski <[email protected]>
>
> ---
>
> Changes in v7:
> - As Luca suggested, simplify the code and related comment.
> ---
> drivers/gpu/drm/display/drm_bridge_connector.c | 16 ++++++++++++----
> 1 file changed, 12 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/display/drm_bridge_connector.c
> b/drivers/gpu/drm/display/drm_bridge_connector.c
> index baacd21e7341..7c2936d59517 100644
> --- a/drivers/gpu/drm/display/drm_bridge_connector.c
> +++ b/drivers/gpu/drm/display/drm_bridge_connector.c
> @@ -673,14 +673,22 @@ struct drm_connector *drm_bridge_connector_init(struct
> drm_device *drm,
> if (!bridge->ycbcr_420_allowed)
> connector->ycbcr_420_allowed = false;
>
> - if (bridge->ops & DRM_BRIDGE_OP_EDID)
> - bridge_connector->bridge_edid = bridge;
> + /*
> + * Ensure the last bridge declares OP_EDID or OP_MODES or both.
> + */
> + if (bridge->ops & DRM_BRIDGE_OP_EDID || bridge->ops &
> DRM_BRIDGE_OP_MODES) {
> + bridge_connector->bridge_edid = NULL;
> + bridge_connector->bridge_modes = NULL;
> + if (bridge->ops & DRM_BRIDGE_OP_EDID)
> + bridge_connector->bridge_edid = bridge;
> + if (bridge->ops & DRM_BRIDGE_OP_MODES)
> + bridge_connector->bridge_modes = bridge;
> + }
> if (bridge->ops & DRM_BRIDGE_OP_HPD)
> bridge_connector->bridge_hpd = bridge;
> if (bridge->ops & DRM_BRIDGE_OP_DETECT)
> bridge_connector->bridge_detect = bridge;
> - if (bridge->ops & DRM_BRIDGE_OP_MODES)
> - bridge_connector->bridge_modes = bridge;
> +
This does not apply on current drm-misc-next, due to the patch I mentioned
in a previous iteration, now applied as commit 2be300f9a0b6 ("drm/display:
bridge_connector: get/put the stored bridges").
However I'm sorry I have to mention that patch turned out being buggy, so
I've sent a series to apply a corrected version [0]. I suggest watching the
disucssion about the fix series, and if that gets approved rebase on top of
that and adapt your changes.
Sorry about the mess. :(
[0]
https://lore.kernel.org/r/20251017-drm-bridge-alloc-getput-bridge-connector-fix-hdmi_cec-v2-0-667abf6d4...@bootlin.com
Luca
--
Luca Ceresoli, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com
