Re: [PATCH v2 3/3] hwmon: (ltc2992) Use fwnode_for_each_available_child_node_scoped()

Andy Shevchenko
2024-05-27T14:31:22Z

Sun, May 26, 2024 at 02:48:51PM +0100, Jonathan Cameron kirjoitti:
> On Thu, 23 May 2024 17:47:16 +0200
> Javier Carrasco <javier.carrasco.cruz@gmail.com> wrote:
>
> > The scoped version of the fwnode_for_each_available_child_node() macro
> > automates object recfount decrement, avoiding possible memory leaks
> > in new error paths inside the loop like it happened when
> > commit '10b029020487 ("hwmon: (ltc2992) Avoid division by zero")'
> > was added.
> >
> > The new macro removes the need to manually call fwnode_handle_put() in
> > the existing error paths and in any future addition. It also removes the
> > need for the current child node declaration as well, as it is internally
> > declared.
> >
> > Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> > Signed-off-by: Javier Carrasco <javier.carrasco.cruz@gmail.com>
>
> This looks like another instances of the lack of clarify about
> what device_for_each_child_node[_scoped]() guarantees about node availability.
> On DT it guarantees the node is available as ultimately calls
> of_get_next_available_child()
>
> On ACPI it doesn't (I think).
> For swnode, there isn't an obvious concept of available.
>
> It would be much better if we reached some agreement on this and
> hence could avoid using the fwnode variants just to get the _available_ form
> as done here.

> Or just add the device_for_each_available_child_node[_scoped]()
> and call that in almost all cases.

device_for_each*() _implies_ availability. You need to talk to Rob about all
this. The design of the device_for_each*() was exactly done in accordance with
his suggestions...

> In generic code, do we ever want to walk unavailable child nodes?

...which are most likely like your question here, i.e. why we ever need to
traverse over unavailable nodes.

--
With Best Regards,
Andy Shevchenko