Re: [PATCH] device property: preserve usecount for node passed to of_fwnode_graph_get_port_parent()

[Sakari Ailus <sakari.ailus@linux.intel.com>]

Hi Niklas,

Niklas Söderlund wrote:
> Using CONFIG_OF_DYNAMIC=y uncovered an imbalance in the usecount of the
> node being passed to of_fwnode_graph_get_port_parent(). Preserve the
> usecount just like it is done in of_graph_get_port_parent().

The of_fwnode_graph_get_port_parent() is called by 
fwnode_graph_get_port_parent() which obtains the port node through 
fwnode_get_parent(). If you take a reference here, calling 
fwnode_graph_get_port_parent() will end up incrementing the port node's 
use count. In other words, my understanding is that dropping the 
reference to the port node isn't a problem but intended behaviour here.

I wonder if I miss something.

>
> Fixes: 3b27d00e7b6d7c88 ("device property: Move fwnode graph ops to firmware specific locations")
> Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
> ---
>  drivers/of/property.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/drivers/of/property.c b/drivers/of/property.c
> index 067f9fab7b77c794..637dcb4833e2af60 100644
> --- a/drivers/of/property.c
> +++ b/drivers/of/property.c
> @@ -922,6 +922,12 @@ of_fwnode_graph_get_port_parent(struct fwnode_handle *fwnode)
>  {
>  	struct device_node *np;
>
> +	/*
> +	 * Preserve usecount for passed in node as of_get_next_parent()
> +	 * will do of_node_put() on it.
> +	 */
> +	of_node_get(to_of_node(fwnode));
> +
>  	/* Get the parent of the port */
>  	np = of_get_next_parent(to_of_node(fwnode));
>  	if (!np)
>


-- 
Sakari Ailus
sakari.ailus@linux.intel.com