linux-kernel - Re: [PATCH 2/8] of: Introduce for_each_*_child_of_node_scoped() to automate of_node

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Date: Mon, 12 Feb 2024 09:20:35 +0100 (CET)
From: Julia Lawall <julia.lawall@...ia.fr>
To: Jonathan Cameron <jic23@...nel.org>
cc: linux-iio@...r.kernel.org, Rob Herring <robh@...nel.org>, 
    Frank Rowand <frowand.list@...il.com>, linux-kernel@...r.kernel.org, 
    Peter Zijlstra <peterz@...radead.org>, 
    Nicolas Palix <nicolas.palix@...g.fr>, 
    Sumera Priyadarsini <sylphrenadin@...il.com>, 
    "Rafael J . Wysocki" <rafael@...nel.org>, Len Brown <lenb@...nel.org>, 
    linux-acpi@...r.kernel.org, 
    Andy Shevchenko <andriy.shevchenko@...ux.intel.com>, 
    Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
    Nuno Sá <nuno.sa@...log.com>, 
    Jonathan Cameron <Jonathan.Cameron@...wei.com>
Subject: Re: [PATCH 2/8] of: Introduce for_each_*_child_of_node_scoped() to
 automate of_node_put() handling



On Sun, 11 Feb 2024, Jonathan Cameron wrote:

> From: Jonathan Cameron <Jonathan.Cameron@...wei.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.
>
> Note that, in the vast majority of cases, the _available_ form should be
> used and as code is converted to these scoped handers, we should confirm
> that any cases that do not check for available have a good reason not
> to.

Is it a good idea to make the two changes at once?  Maybe it would slow
down the use of the scoped form, which can really simplify the code.

julia

>
> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> ---
>  include/linux/of.h | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
>
> diff --git a/include/linux/of.h b/include/linux/of.h
> index 50e882ee91da..024dda54b9c7 100644
> --- a/include/linux/of.h
> +++ b/include/linux/of.h
> @@ -1430,10 +1430,23 @@ static inline int of_property_read_s32(const struct device_node *np,
>  #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))
> +
> +#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_child(parent, child))
> +
>  #define for_each_available_child_of_node(parent, child) \
>  	for (child = of_get_next_available_child(parent, NULL); child != NULL; \
>  	     child = of_get_next_available_child(parent, child))
>
> +#define for_each_available_child_of_node_scoped(parent, child) \
> +	for (struct device_node *child __free(device_node) =		\
> +	     of_get_next_available_child(parent, NULL);			\
> +	     child != NULL;						\
> +	     child = of_get_next_available_child(parent, child))
> +
>  #define for_each_of_cpu_node(cpu) \
>  	for (cpu = of_get_next_cpu_node(NULL); cpu != NULL; \
>  	     cpu = of_get_next_cpu_node(cpu))
> --
> 2.43.1
>
>