Re: [PATCH v4 1/2] device property: Add scoped fwnode child node iterators

Jean-François Lessard
2025-09-03T16:44:00Z

Hi Sakari,

Le 3 septembre 2025 09 h 18 min 32 s HAE, Sakari Ailus <sakari.ailus@linux.intel.com> a écrit :
>Hi Jean-François,
>
>On Tue, Sep 02, 2025 at 03:04:39PM -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_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@gmail.com>
>> ---
>>
>> Notes:
>> checkpatch reports false positives that are intentionally ignored:
>> MACRO_ARG_REUSE, MACRO_ARG_PRECEDENCE
>> This is a standard iterator pattern following kernel conventions.
>>
>> include/linux/property.h | 10 ++++++++++
>> 1 file changed, 10 insertions(+)
>>
>> diff --git a/include/linux/property.h b/include/linux/property.h
>> index 82f0cb3ab..862e20813 100644
>> --- a/include/linux/property.h
>> +++ b/include/linux/property.h
>> @@ -176,6 +176,16 @@ 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_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))
>> +
>
>Do we really need the available variant?
>
>Please see
><URL:https://lore.kernel.org/linux-acpi/Zwj12J5bTNUEnxA0@kekkonen.localdomain/>.
>
>I'll post a patch to remove fwnode_get_next_available_child_node(), too.
>

Thanks for the link to the discussion.

I see you're planning to remove fwnode_get_next_available_child_node()
entirely. In that context, adding a scoped version doesn't make sense.

For my driver use case, I can handle the status checking manually if
the _available_ variant is being deprecated.

Should I drop the _available_ variant and submit v5 with only
fwnode_for_each_child_node_scoped()?

>> struct fwnode_handle *device_get_next_child_node(const struct device *dev,
>> struct fwnode_handle *child);
>>
>