Re: [PATCH v3 2/5] drm/bridge: aux: Add drm_aux_bridge_register_from_node()

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] Unbalanced `of_node_put()` in `drm_aux_bridge_register_from_node()` and `drm_aux_bridge_release()` causes a reference count underflow for the provided `device_node`.
--

--- Patch [2]: [PATCH v3 2/5] drm/bridge: aux: Add drm_aux_bridge_register_from_node() ---
commit b2b66972200bdc4b6541ca41f8ae44c08d81a964
Author: Chaoyi Chen <chaoyi.chen@rock-chips.com>

drm/bridge: aux: Add drm_aux_bridge_register_from_node()

The drm_aux_bridge_register() uses the device->of_node as the bridge->of_node.
This patch adds drm_aux_bridge_register_from_node() to allow specifying the
of_node corresponding to the bridge.

> diff --git a/drivers/gpu/drm/bridge/aux-bridge.c b/drivers/gpu/drm/bridge/aux-bridge.c
> index 1ed21a8713bfd..06a1466f49bd2 100644
> --- a/drivers/gpu/drm/bridge/aux-bridge.c
> +++ b/drivers/gpu/drm/bridge/aux-bridge.c
[ ... ]
> @@ -62,7 +63,10 @@ int drm_aux_bridge_register(struct device *parent)
>  	adev->dev.parent = parent;
>  	adev->dev.release = drm_aux_bridge_release;
>  
> -	device_set_of_node_from_dev(&adev->dev, parent);
> +	if (np)
> +		device_set_node(&adev->dev, of_fwnode_handle(np));

[Severity: High]
Does this cause a reference count underflow for the device node?

Unlike device_set_of_node_from_dev() which safely acquires a reference to the
of_node, device_set_node() just assigns the pointer without calling
of_node_get().

If auxiliary_device_init() fails, the error path below unconditionally calls
of_node_put(adev->dev.of_node). Similarly, the pre-existing
drm_aux_bridge_release() callback drops a reference when the device is
destroyed.

Could this cause of_node_put() to drop a reference that was never acquired?

> +	else
> +		device_set_of_node_from_dev(&adev->dev, parent);
>  
>  	ret = auxiliary_device_init(adev);
>  	if (ret) {

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260717072323.96-1-kernel@airkyi.com?part=2

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