linux-kernel - Re: Usage of for_each_child_of

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Date:	Sat, 12 Oct 2013 22:15:03 -0500
From:	Rob Herring <robherring2@...il.com>
To:	Guenter Roeck <linux@...ck-us.net>
Cc:	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Grant Likely <grant.likely@...aro.org>,
	Rob Herring <rob.herring@...xeda.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: Usage of for_each_child_of_node()

On Sat, Oct 12, 2013 at 3:54 PM, Guenter Roeck <linux@...ck-us.net> wrote:
> Hi all,
>
> for_each_child_of_node() and similar functions increase the refcount
> on each returned node and expect the caller to release the node by
> calling of_node_put() when done.
>
> Looking through the kernel code, it appears this is hardly ever done,
> if at all. Some code even calls of_node_get() on returned nodes again.
>
> I guess this doesn't matter in cases where devicetree is a static entity.
> However, this is not (or no longer) the case with devicetree overlays,
> or more generically in cases where devicetree nodes are added and
> removed dynamically.
>
> Fundamental question: Would patches to fix this problem be accepted upstream
> ?

Certainly.

> Or, of course, stepping a bit back: Am I missing something essential ?

No. I think this is frequently wrong since it typically doesn't matter
for static entries as you mention.

Rob
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