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    SubjectRe: [RFC PATCH 2/5] of: Introduce for_each_child_of_node_scoped() to automate of_node_put() handling
    On Sun, 28 Jan 2024 15:11:01 -0600
    David Lechner <dlechner@baylibre.com> wrote:

    > On Sun, Jan 28, 2024 at 10:06 AM Jonathan Cameron <jic23@kernel.org> wrote:
    > >
    > > From: Jonathan Cameron <Jonathan.Cameron@huawei.com>
    > >
    > > To avoid issues with out of order cleanup, or ambiguity about when the
    > > auto freed data is first instantiated, do it within the for loop definition.
    > >
    > > The disadvantage is that the struct device_node *child variable creation
    > > is not immediately obvious where this is used.
    > > However, in many cases, if there is another definition of
    > > struct device_node *child; the compiler / static analysers will notify us
    > > that it is unused, or uninitialized.
    > >
    > > Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
    > > ---
    > > include/linux/of.h | 6 ++++++
    > > 1 file changed, 6 insertions(+)
    > >
    > > diff --git a/include/linux/of.h b/include/linux/of.h
    > > index 50e882ee91da..f822226eac6d 100644
    > > --- a/include/linux/of.h
    > > +++ b/include/linux/of.h
    > > @@ -1434,6 +1434,12 @@ static inline int of_property_read_s32(const struct device_node *np,
    > > for (child = of_get_next_available_child(parent, NULL); child != NULL; \
    > > child = of_get_next_available_child(parent, child))
    > >
    > > +#define for_each_child_of_node_scoped(parent, child) \
    > > + for (struct device_node *child __free(device_node) = \
    > > + of_get_next_child(parent, NULL); \
    > > + child != NULL; \
    > > + child = of_get_next_available_child(parent, child))
    >
    > Doesn't this need to match the initializer (of_get_next_child)?
    > Otherwise it seems like the first node could be a disabled node but no
    > other disabled nodes would be included in the iteration.

    FwIW that was was entirely unintentional. Not sure how it happened :(
    Anyhow, now will be for_each_available_child_of_node_scoped() with the
    right first call.

    >
    > It seems like we would want two macros, one for each variation,
    > analogous to for_each_child_of_node() and
    > for_each_available_child_of_node().
    >
    >
    > > +
    > > #define for_each_of_cpu_node(cpu) \
    > > for (cpu = of_get_next_cpu_node(NULL); cpu != NULL; \
    > > cpu = of_get_next_cpu_node(cpu))
    > > --
    > > 2.43.0
    > >
    > >


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