[alsa-devel] [PATCH] device property: Fix usecount for of_graph_get_port_parent()

[Tony Lindgren]

* Rob Herring <robh+dt at kernel.org> [170727 15:19]:
> On Thu, Jul 27, 2017 at 4:44 AM, Tony Lindgren <tony at atomide.com> wrote:
> > --- a/drivers/of/property.c
> > +++ b/drivers/of/property.c
> > @@ -708,6 +708,15 @@ struct device_node *of_graph_get_port_parent(struct device_node *node)
> >  {
> >         unsigned int depth;
> >
> > +       if (!node)
> > +               return NULL;
> > +
> > +       /*
> > +        * Preserve usecount for passed in node as of_get_next_parent()
> > +        * will do of_node_put() on it.
> > +        */
> > +       of_node_get(node);
> 
> I think this messes up of_graph_get_remote_port_parent(). First it
> calls of_graph_get_remote_endpoint which returns the endpoint node
> with ref count incremented. Then you are incrementing it again here.

Hmm OK looks like I missed that one. If we want to have
of_graph_get_port_parent not trash the node passed to it, we should
just change things there too:

struct device_node *of_graph_get_remote_port_parent(
		const struct device_node *node)
{
	struct device_node *np, *pp;

	/* Get remote endpoint node. */
	np = of_graph_get_remote_endpoint(node);

	pp = of_graph_get_port_parent(np);
	of_node_put(np);

	return pp;
}
EXPORT_SYMBOL(of_graph_get_remote_port_parent);

Does that make sense to you?

> > diff --git a/sound/soc/generic/audio-graph-card.c b/sound/soc/generic/audio-graph-card.c
> > --- a/sound/soc/generic/audio-graph-card.c
> > +++ b/sound/soc/generic/audio-graph-card.c
> > @@ -224,7 +224,6 @@ static int asoc_graph_card_parse_of(struct graph_card_data *priv)
> >
> >         of_for_each_phandle(&it, rc, node, "dais", NULL, 0) {
> >                 ret = asoc_graph_card_dai_link_of(it.node, priv, idx++);
> > -               of_node_put(it.node);
> >                 if (ret < 0)
> >                         return ret;
> 
> I think you need a put here.

Do you mean on error it should be as below, right?

	ret = asoc_graph_card_dai_link_of(it.node, priv, idx++);
	if (ret < 0) {
		of_node_put(it.node);
		return ret;
	}

Regards,

Tony