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Date: Sun, 4 Feb 2024 19:56:11 +0000
From: Jonathan Cameron <jic23@kernel.org>
To: David Lechner <dlechner@baylibre.com>
Cc: linux-iio@vger.kernel.org, Rob Herring <robh@kernel.org>, Frank Rowand
 <frowand.list@gmail.com>, linux-kernel@vger.kernel.org, Julia Lawall
 <Julia.Lawall@inria.fr>, Nicolas Palix <nicolas.palix@imag.fr>, Sumera
 Priyadarsini <sylphrenadin@gmail.com>, "Rafael J . Wysocki"
 <rafael@kernel.org>, Len Brown <lenb@kernel.org>,
 linux-acpi@vger.kernel.org, Andy Shevchenko
 <andriy.shevchenko@linux.intel.com>, Greg Kroah-Hartman
 <gregkh@linuxfoundation.org>, Nuno =?UTF-8?B?U8Oh?= <nuno.sa@analog.com>,
 Jonathan Cameron <Jonathan.Cameron@huawei.com>
Subject: Re: [RFC PATCH 2/5] of: Introduce for_each_child_of_node_scoped()
 to automate of_node_put() handling
Message-ID: <20240204195611.2bb6ff58@jic23-huawei>
In-Reply-To: <CAMknhBEL3cv4L0A-W=_1EcDmD3Cj8apheDcpnqjyJjKBZuPYew@mail.gmail.com>
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	<CAMknhBEL3cv4L0A-W=_1EcDmD3Cj8apheDcpnqjyJjKBZuPYew@mail.gmail.com>
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On Sun, 28 Jan 2024 15:11:01 -0600
David Lechner <dlechner@baylibre.com> wrote:

> On Sun, Jan 28, 2024 at 10:06=E2=80=AFAM Jonathan Cameron <jic23@kernel.o=
rg> wrote:
> >
> > From: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> >
> > To avoid issues with out of order cleanup, or ambiguity about when the
> > auto freed data is first instantiated, do it within the for loop defini=
tion.
> >
> > The disadvantage is that the struct device_node *child variable creation
> > is not immediately obvious where this is used.
> > However, in many cases, if there is another definition of
> > struct device_node *child; the compiler / static analysers will notify =
us
> > that it is unused, or uninitialized.
> >
> > Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> > ---
> >  include/linux/of.h | 6 ++++++
> >  1 file changed, 6 insertions(+)
> >
> > diff --git a/include/linux/of.h b/include/linux/of.h
> > index 50e882ee91da..f822226eac6d 100644
> > --- a/include/linux/of.h
> > +++ b/include/linux/of.h
> > @@ -1434,6 +1434,12 @@ static inline int of_property_read_s32(const str=
uct device_node *np,
> >         for (child =3D of_get_next_available_child(parent, NULL); child=
 !=3D NULL; \
> >              child =3D of_get_next_available_child(parent, child))
> >
> > +#define for_each_child_of_node_scoped(parent, child) \
> > +       for (struct device_node *child __free(device_node) =3D         =
   \
> > +            of_get_next_child(parent, NULL);                          =
 \
> > +            child !=3D NULL;                                          =
   \
> > +            child =3D of_get_next_available_child(parent, child)) =20
>=20
> Doesn't this need to match the initializer (of_get_next_child)?
> Otherwise it seems like the first node could be a disabled node but no
> other disabled nodes would be included in the iteration.

FwIW that was was entirely unintentional.  Not sure how it happened :(
Anyhow, now will be for_each_available_child_of_node_scoped() with the
right first call.

>=20
> It seems like we would want two macros, one for each variation,
> analogous to for_each_child_of_node() and
> for_each_available_child_of_node().
>=20
>=20
> > +
> >  #define for_each_of_cpu_node(cpu) \
> >         for (cpu =3D of_get_next_cpu_node(NULL); cpu !=3D NULL; \
> >              cpu =3D of_get_next_cpu_node(cpu))
> > --
> > 2.43.0
> >
> > =20