Re: [PATCH -next 1/5] drm/rockchip: Use for_each_child_of_node_scoped()

[Jonathan Cameron <Jonathan.Cameron@Huawei.com>]

On Fri, 23 Aug 2024 17:20:49 +0800
Jinjie Ruan <ruanjinjie@huawei.com> wrote:

> Avoids the need for manual cleanup of_node_put() in early exits
> from the loop.
> 
> Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>

There is more to do here, and looking at the code, I'm far from
sure it isn't releasing references it never had.

> ---
>  drivers/gpu/drm/rockchip/rockchip_lvds.c | 8 +++-----
>  1 file changed, 3 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/rockchip/rockchip_lvds.c b/drivers/gpu/drm/rockchip/rockchip_lvds.c
> index 9a01aa450741..f5b3f18794dd 100644
> --- a/drivers/gpu/drm/rockchip/rockchip_lvds.c
> +++ b/drivers/gpu/drm/rockchip/rockchip_lvds.c
> @@ -548,7 +548,7 @@ static int rockchip_lvds_bind(struct device *dev, struct device *master,
>  	struct drm_encoder *encoder;
>  	struct drm_connector *connector;
>  	struct device_node *remote = NULL;
> -	struct device_node  *port, *endpoint;

Odd extra space before *port in original. Clean that up whilst here.


> +	struct device_node  *port;

Use __free(device_node) for *port as well.

So where the current asignment is.
	struct device_node *port = of_graph_get_port_by_id(dev->of_node, 1);

>  	int ret = 0, child_count = 0;
>  	const char *name;
>  	u32 endpoint_id = 0;
> @@ -560,15 +560,13 @@ static int rockchip_lvds_bind(struct device *dev, struct device *master,
>  			      "can't found port point, please init lvds panel port!\n");
>  		return -EINVAL;
>  	}
> -	for_each_child_of_node(port, endpoint) {
> +	for_each_child_of_node_scoped(port, endpoint) {
>  		child_count++;
>  		of_property_read_u32(endpoint, "reg", &endpoint_id);
>  		ret = drm_of_find_panel_or_bridge(dev->of_node, 1, endpoint_id,
>  						  &lvds->panel, &lvds->bridge);
> -		if (!ret) {
> -			of_node_put(endpoint);
> +		if (!ret)
>  			break;

This then can simply be
			return dev_err_probe(dev, ret,
					     "failed to find pannel and bridge node\n");
> -		}

Various other paths become direct returns as well.

>  	}

The later code with remote looks suspect as not obvious who got the reference that
is being put but assuming that is correct, it's another possible place for __free based
cleanup.


>  	if (!child_count) {
>  		DRM_DEV_ERROR(dev, "lvds port does not have any children\n");