linux-kernel - Re: fwnode_for_each_child_node() and OF backend discrepancy

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Message-ID: <b8ec04dc-f803-ee2c-29b7-b0311eb8c5fb@linaro.org>
Date:   Mon, 27 Jun 2022 15:08:33 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Michael Walle <michael@...le.cc>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>
Cc:     linux-acpi@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: fwnode_for_each_child_node() and OF backend discrepancy

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")
.

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

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

However maybe ACPI treats it somehow differently?

Best regards,
Krzysztof