On Fri, Aug 29, 2025 at 07:34:17AM -0400, Jean-François Lessard wrote:
> Le 29 août 2025 00 h 23 min 22 s HAE, Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> a écrit :
> >On Thu, Aug 28, 2025 at 10:17:59PM -0400, Jean-François Lessard wrote:
> >> Add scoped versions of fwnode child node iterators that automatically
> >> handle reference counting cleanup using the __free() attribute:
> >>
> >> - fwnode_for_each_child_node_scoped()
> >> - fwnode_for_each_named_child_node_scoped()
> >> - fwnode_for_each_available_child_node_scoped()
> >>
> >> These macros follow the same pattern as existing scoped iterators in the
> >> kernel, ensuring fwnode references are automatically released when the
> >> iterator variable goes out of scope. This prevents resource leaks and
> >> eliminates the need for manual cleanup in error paths.
> >>
> >> The implementation mirrors the non-scoped variants but uses
> >> __free(fwnode_handle) for automatic resource management, providing a safer
> >> and more convenient interface for drivers iterating over firmware node
> >> children.
> >>
> >> Signed-off-by: Jean-François Lessard <jefflessard3@xxxxxxxxx>
> >> ---
> >>
> >> Notes:
> >> checkpatch reports false positives that are intentionally ignored:
> >> COMPLEX_MACRO, MACRO_ARG_REUSE, MACRO_ARG_PRECEDENCE
> >> This is a standard iterator pattern following kernel conventions.
> >>
> >> include/linux/property.h | 14 ++++++++++++++
> >> 1 file changed, 14 insertions(+)
> >>
> >> diff --git a/include/linux/property.h b/include/linux/property.h
> >> index 82f0cb3ab..279c244db 100644
> >> --- a/include/linux/property.h
> >> +++ b/include/linux/property.h
> >> @@ -176,6 +176,20 @@ struct fwnode_handle *fwnode_get_next_available_child_node(
> >> for (child = fwnode_get_next_available_child_node(fwnode, NULL); child;\
> >> child = fwnode_get_next_available_child_node(fwnode, child))
> >>
> >> +#define fwnode_for_each_child_node_scoped(fwnode, child) \
> >> + for (struct fwnode_handle *child __free(fwnode_handle) = \
> >> + fwnode_get_next_child_node(fwnode, NULL); \
> >> + child; child = fwnode_get_next_child_node(fwnode, child))
> >> +
> >> +#define fwnode_for_each_named_child_node_scoped(fwnode, child, name) \
> >> + fwnode_for_each_child_node_scoped(fwnode, child) \
> >> + for_each_if(fwnode_name_eq(child, name))
> >> +
> >> +#define fwnode_for_each_available_child_node_scoped(fwnode, child) \
> >> + for (struct fwnode_handle *child __free(fwnode_handle) = \
> >> + fwnode_get_next_available_child_node(fwnode, NULL); \
> >> + child; child = fwnode_get_next_available_child_node(fwnode, child))
> >> +
> >> struct fwnode_handle *device_get_next_child_node(const struct device *dev,
> >> struct fwnode_handle *child);
> >>
> >
> >We need a real user of this before we can add them, so please do that as
> >part of a patch series.
> >
>
> I understand the "no dead code" policy, but I found existing manual
> implementations of this exact pattern in the current kernel.
>
> For example, drivers/i2c/i2c-core-slave.c already does:
>
> struct fwnode_handle *child __free(fwnode_handle) = NULL;
> ...
> fwnode_for_each_child_node(fwnode, child) {
> ...
> }
>
> This suggests developers are already wanting this functionality but
> implementing it manually.
Great, then add it here and fix up drivers/i2c/i2c-core-slave.c to use
it!
thanks,
greg k-h
