Re: [PATCH RFC v2 3/4] drm/bridge: Wire drmm_connector_dp_init() via new DRM_BRIDGE_OP_DP flag

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:
- [High] Unconditional call to drmm_connector_dp_init() breaks bridge chains with downstream format converters.
- [Low] Kernel-doc for DRM_BRIDGE_OP_DP incorrectly references a non-existent structure member.
--

commit 95b54bb01e2f24e6a00ddf825b25aaa6985fa864
Author: Kory Maincent <kory.maincent@bootlin.com>

drm/bridge: Wire drmm_connector_dp_init() via new DRM_BRIDGE_OP_DP flag
    
Introduce DRM_BRIDGE_OP_DP to indicate bridges that provide DP connector
operations. Update drm_bridge_connector_init() to use
drmm_connector_dp_init() when this flag is present to expose link training
state properties.

> diff --git a/drivers/gpu/drm/display/drm_bridge_connector.c b/drivers/gpu/drm/display/drm_bridge_connector.c
> index 39cc18f78eda1..5238b1ec738ce 100644
> --- a/drivers/gpu/drm/display/drm_bridge_connector.c
> +++ b/drivers/gpu/drm/display/drm_bridge_connector.c

[ ... ]

> @@ -986,6 +1003,13 @@ struct drm_connector *drm_bridge_connector_init(struct drm_device *drm,
>  					       max_bpc);
>  		if (ret)
>  			return ERR_PTR(ret);
> +	} else if (bridge_connector->bridge_dp) {
> +		ret = drmm_connector_dp_init(drm, connector,
> +					     &drm_bridge_connector_funcs,
> +					     bridge_connector->bridge_dp->dp_link_caps,
> +					     connector_type, ddc);
> +		if (ret)
> +			return ERR_PTR(ret);

[Severity: High]
If a DRM bridge chain consists of a DisplayPort transmitter followed by a
format-converting bridge (e.g., DP-to-VGA or DP-to-LVDS), the final
connector_type of the chain will be the output format (like
DRM_MODE_CONNECTOR_VGA).

Since drmm_connector_dp_init() explicitly enforces that connector_type must
be DRM_MODE_CONNECTOR_DisplayPort or DRM_MODE_CONNECTOR_eDP, will this call
immediately return -EINVAL and break display initialization for legitimate
format-converted hardware combinations?

Does the branch condition need to verify the final connector_type is actually
DP/eDP before forcing the DP initialization path?

>  	} else {
>  		ret = drmm_connector_init(drm, connector,

[ ... ]

> diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h
> index a8d67bd9ee505..63db754d21146 100644
> --- a/include/drm/drm_bridge.h
> +++ b/include/drm/drm_bridge.h
> @@ -1092,6 +1092,14 @@ enum drm_bridge_ops {
>  	 * &drm_bridge_funcs->hdmi_clear_spd_infoframe callbacks.
>  	 */
>  	DRM_BRIDGE_OP_HDMI_SPD_INFOFRAME = BIT(10),
> +	/**
> +	 * @DRM_BRIDGE_OP_DP: The bridge provides DisplayPort connector
> +	 * operations, including link training support. Bridges that set
> +	 * this flag must provide DisplayPort-related information and
> +	 * fill the &drm_bridge->dp_link_train_caps link training

[Severity: Low]
This isn't a bug, but there's a typo in the documentation. It references
&drm_bridge->dp_link_train_caps, but the actual structure member added
in this patch is named dp_link_caps.

> +	 * capabilities.
> +	 */
> +	DRM_BRIDGE_OP_DP = BIT(11),
>  };

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260619-feat_link_cap-v2-0-a3dec4c02ad9@bootlin.com?part=3