Quoting Jacopo Mondi (2023-08-28 08:34:40)
> Hi Christophe
>
> On Sat, Aug 26, 2023 at 12:13:40AM +0200, Christophe JAILLET wrote:
> > This is odd to have a of_node_put() just after a for_each_child_of_node()
> > or a for_each_endpoint_of_node() loop. It should already be called
> > during the last iteration.
>
> Let's unwrap the calls:
>
> #define for_each_child_of_node(parent, child) \
> for (child = of_get_next_child(parent, NULL); child != NULL; \
> child = of_get_next_child(parent, child))
>
> static struct device_node *__of_get_next_child(const struct device_node *node,
> struct device_node *prev)
> {
> struct device_node *next;
>
> if (!node)
> return NULL;
>
> next = prev ? prev->sibling : node->child;
> of_node_get(next);
> of_node_put(prev);
> return next;
> }
>
> Let's express the C for loop semantic as a while to help following the
> code:
>
> child = of_get_next_child(parent, NULL);
> while (child != NULL)
> child = of_get_next_child(parent, child);
>
> I concur that the last loop iteration the call to
> __of_get_next_child() will expand to
>
> next = NULL;
> of_node_get(NULL);
> of_node_put(prev)
>
> So it seems to me it is not necessary to put the node after
> for_each_child_of_node() ?
>
> In facts none of the other usages of for_each_child_of_node() in the
> kernel (the ones i checked at least) have a put() after the loop.
I agree. As long as the loops don't use any break statement - there
shouldn't be any _put() after the completion of the loop.
That would make a good cocci script - make sure these iterators do not
use 'break' internally - as that would then conflict!
Reviewed-by: Kieran Bingham <kieran.bingham+renesas@xxxxxxxxxxxxxxxx>
>
> >
> > Remove these calls.
> >
> > Fixes: 66d8c9d2422d ("media: i2c: Add MAX9286 driver")
> > Signed-off-by: Christophe JAILLET <christophe.jaillet@xxxxxxxxxx>
>
> Reviewed-by: Jacopo Mondi <jacopo.mondi@xxxxxxxxxxxxxxxx>
>
> Thanks
> j
>
> > ---
> > /!\ This patch is speculative, review with case /!\
> > ---
> > drivers/media/i2c/max9286.c | 2 --
> > 1 file changed, 2 deletions(-)
> >
> > diff --git a/drivers/media/i2c/max9286.c b/drivers/media/i2c/max9286.c
> > index 20e7c7cf5eeb..f27a69b1b727 100644
> > --- a/drivers/media/i2c/max9286.c
> > +++ b/drivers/media/i2c/max9286.c
> > @@ -1450,7 +1450,6 @@ static int max9286_parse_dt(struct max9286_priv *priv)
> >
> > i2c_mux_mask |= BIT(id);
> > }
> > - of_node_put(node);
> > of_node_put(i2c_mux);
> >
> > /* Parse the endpoints */
> > @@ -1514,7 +1513,6 @@ static int max9286_parse_dt(struct max9286_priv *priv)
> > priv->source_mask |= BIT(ep.port);
> > priv->nsources++;
> > }
> > - of_node_put(node);
> >
> > of_property_read_u32(dev->of_node, "maxim,bus-width", &priv->bus_width);
> > switch (priv->bus_width) {
> > --
> > 2.34.1
> >
