Re: [PATCH v4] drm/bridge: imx8qxp-pxl2dpi: avoid ERR_PTR with device_node cleanup

[Liu Ying <victor.liu@nxp.com>]

On Tue, May 05, 2026 at 04:21:45PM +0800, Guangshuo Li wrote:
> imx8qxp_pxl2dpi_get_available_ep_from_port() returns ERR_PTR()
> on errors. imx8qxp_pxl2dpi_find_next_bridge() stores its return
> value in a __free(device_node) variable before checking IS_ERR().
> When the function returns on the error path, the cleanup action calls
> of_node_put() on the ERR_PTR() value.
> 
> Do not let a device_node cleanup variable hold error pointers. Return
> the error code from imx8qxp_pxl2dpi_get_available_ep_from_port()
> directly and pass the endpoint node through an output argument. This
> keeps the cleanup action operating only on NULL or a valid device_node,
> while preserving the existing error codes.
> 
> Fixes: ceea3f7806a10 ("drm/bridge: imx8qxp-pxl2dpi: simplify put of device_node pointers")
> Cc: stable@vger.kernel.org
> Reviewed-by: Frank Li <Frank.Li@nxp.com>
> Signed-off-by: Guangshuo Li <lgs201920130244@gmail.com>
> ---
> v4:
>   - Drop the sentence mentioning the custom static analysis tool.
>   - Add Frank's Reviewed-by tag.
>   - No functional code changes.
> 
> v3:
>   - Do not change DEFINE_FREE(device_node, ...).
>   - Fix the driver pattern by making
>     imx8qxp_pxl2dpi_get_available_ep_from_port() return an int and
>     pass the endpoint via an output argument.
>   - Update both callers so __free(device_node) never holds ERR_PTR().
> 
> v2:
>   - Fix DEFINE_FREE(device_node, ...) directly.
> 
>  drivers/gpu/drm/bridge/imx/imx8qxp-pxl2dpi.c | 54 ++++++++++----------
>  1 file changed, 26 insertions(+), 28 deletions(-)
> 
> diff --git a/drivers/gpu/drm/bridge/imx/imx8qxp-pxl2dpi.c b/drivers/gpu/drm/bridge/imx/imx8qxp-pxl2dpi.c
> index 441fd32dc91c..881ebb811eb3 100644
> --- a/drivers/gpu/drm/bridge/imx/imx8qxp-pxl2dpi.c
> +++ b/drivers/gpu/drm/bridge/imx/imx8qxp-pxl2dpi.c
> @@ -222,52 +222,52 @@ static const struct drm_bridge_funcs imx8qxp_pxl2dpi_bridge_funcs = {
>  			imx8qxp_pxl2dpi_bridge_atomic_get_output_bus_fmts,
>  };
>  
> -static struct device_node *
> +static int
>  imx8qxp_pxl2dpi_get_available_ep_from_port(struct imx8qxp_pxl2dpi *p2d,
> -					   u32 port_id)
> +					   u32 port_id,
> +					   struct device_node **ep)
>  {
> -	struct device_node *port, *ep;
> +	struct device_node *port __free(device_node) =

Can you provide a minimal fix for stable tree by not using the cleanup
action?  You can add the cleanup action with follow-up patch(es).

> +		of_graph_get_port_by_id(p2d->dev->of_node, port_id);
>  	int ep_cnt;
>  
> -	port = of_graph_get_port_by_id(p2d->dev->of_node, port_id);
> +	*ep = NULL;
>  	if (!port) {
>  		DRM_DEV_ERROR(p2d->dev, "failed to get port@%u\n", port_id);
> -		return ERR_PTR(-ENODEV);
> +		return -ENODEV;
>  	}
>  
>  	ep_cnt = of_get_available_child_count(port);
>  	if (ep_cnt == 0) {
>  		DRM_DEV_ERROR(p2d->dev, "no available endpoints of port@%u\n",
>  			      port_id);
> -		ep = ERR_PTR(-ENODEV);
> -		goto out;
> +		return -ENODEV;
>  	} else if (ep_cnt > 1) {
>  		DRM_DEV_ERROR(p2d->dev,
>  			      "invalid available endpoints of port@%u\n",
>  			      port_id);
> -		ep = ERR_PTR(-EINVAL);
> -		goto out;
> +		return -EINVAL;
>  	}
>  
> -	ep = of_get_next_available_child(port, NULL);
> -	if (!ep) {
> +	*ep = of_get_next_available_child(port, NULL);
> +	if (!*ep) {
>  		DRM_DEV_ERROR(p2d->dev,
>  			      "failed to get available endpoint of port@%u\n",
>  			      port_id);
> -		ep = ERR_PTR(-ENODEV);
> -		goto out;
> +		return -ENODEV;
>  	}
> -out:
> -	of_node_put(port);
> -	return ep;
> +
> +	return 0;
>  }
>  
>  static int imx8qxp_pxl2dpi_find_next_bridge(struct imx8qxp_pxl2dpi *p2d)
>  {
> -	struct device_node *ep __free(device_node) =
> -		imx8qxp_pxl2dpi_get_available_ep_from_port(p2d, 1);
> -	if (IS_ERR(ep))
> -		return PTR_ERR(ep);
> +	struct device_node *ep __free(device_node) = NULL;

Why do you need to initialize ep to NULL?

> +	int ret;
> +
> +	ret = imx8qxp_pxl2dpi_get_available_ep_from_port(p2d, 1, &ep);
> +	if (ret)
> +		return ret;
>  
>  	struct device_node *remote __free(device_node) = of_graph_get_remote_port_parent(ep);
>  	if (!remote || !of_device_is_available(remote)) {
> @@ -287,26 +287,24 @@ static int imx8qxp_pxl2dpi_find_next_bridge(struct imx8qxp_pxl2dpi *p2d)
>  
>  static int imx8qxp_pxl2dpi_set_pixel_link_sel(struct imx8qxp_pxl2dpi *p2d)
>  {
> -	struct device_node *ep;
> +	struct device_node *ep __free(device_node) = NULL;

Same here:
- Can you provide a minimal fix for stable tree?
- Why do you need to initialize ep to NULL?

>  	struct of_endpoint endpoint;
>  	int ret;
>  
> -	ep = imx8qxp_pxl2dpi_get_available_ep_from_port(p2d, 0);
> -	if (IS_ERR(ep))
> -		return PTR_ERR(ep);
> +	ret = imx8qxp_pxl2dpi_get_available_ep_from_port(p2d, 0, &ep);
> +	if (ret)
> +		return ret;
>  
>  	ret = of_graph_parse_endpoint(ep, &endpoint);
>  	if (ret) {
>  		DRM_DEV_ERROR(p2d->dev,
>  			      "failed to parse endpoint of port@0: %d\n", ret);
> -		goto out;
> +		return ret;
>  	}
>  
>  	p2d->pl_sel = endpoint.id;
> -out:
> -	of_node_put(ep);
>  
> -	return ret;
> +	return 0;
>  }
>  
>  static int imx8qxp_pxl2dpi_parse_dt_companion(struct imx8qxp_pxl2dpi *p2d)
> -- 
> 2.43.0
> 

-- 
Regards,
Liu Ying