Re: fwnode_for_each_child_node() and OF backend discrepancy

Rafael J. Wysocki
2022-06-27T13:33:56Z

On Mon, Jun 27, 2022 at 3:08 PM Krzysztof Kozlowski
<krzysztof.kozlowski@linaro.org> wrote:
>
> On 27/06/2022 14:49, Michael Walle wrote:
> > Hi,
> >
> > I tired to iterate over all child nodes, regardless if they are
> > available
> > or not. Now there is that handy fwnode_for_each_child_node() (and the
> > fwnode_for_each_available_child_node()). The only thing is the OF
> > backend
> > already skips disabled nodes [1], making fwnode_for_each_child_node()
> > and
> > fwnode_for_each_available_child_node() behave the same with the OF
> > backend.
> >
> > Doesn't seem to be noticed by anyone for now. I'm not sure how to fix
> > that
> > one. fwnode_for_each_child_node() and also fwnode_get_next_child_node()
> > are
> > used by a handful of drivers. I've looked at some, but couldn't decide
> > whether they really want to iterate over all child nodes or just the
> > enabled
> > ones.
>
> If I get it correctly, this was introduced by 8a0662d9ed29 ("Driver
> core: Unified interface for firmware node properties")
> .

Originally it was, but then it has been reworked a few times.

The backend callbacks were introduced by Sakari, in particular.

> The question to Rafael - what was your intention when you added
> device_get_next_child_node() looking only for available nodes?

That depends on the backend.

fwnode_for_each_available_child_node() is more specific and IIRC it
was introduced for fw_devlink (CC Saravana).

> My understanding is that this implementation should be consistent with
> OF implementation, so fwnode_get_next_child_node=get any child.

IIUC, the OF implementation is not consistent with the
fwnode_get_next_child_node=get any child thing.

> However maybe ACPI treats it somehow differently?

acpi_get_next_subnode() simply returns the next subnode it can find.