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Date: Sun, 4 Feb 2024 20:52:20 +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: <20240204203418.00464af4@jic23-huawei>
In-Reply-To: <20240204195611.2bb6ff58@jic23-huawei>
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On Sun, 4 Feb 2024 19:56:11 +0000
Jonathan Cameron <jic23@kernel.org> wrote:

> On Sun, 28 Jan 2024 15:11:01 -0600
> David Lechner <dlechner@baylibre.com> wrote:
>=20
> > On Sun, Jan 28, 2024 at 10:06=E2=80=AFAM Jonathan Cameron <jic23@kernel=
org> wrote: =20
> > >
> > > 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 defi=
nition.
> > >
> > > The disadvantage is that the struct device_node *child variable creat=
ion
> > > 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 notif=
y 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 s=
truct device_node *np,
> > >         for (child =3D of_get_next_available_child(parent, NULL); chi=
ld !=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. =20
>=20
> 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.

*sigh* Which I can't use for the unittest case (tests fail as a result
as some nodes that need to be covered are not available) so both will need =
to exist
though we can hopefully review each change for whether the appropriate one
is used afterwards (ignoring whether it was with the non scoped versions)

Jonathan

>=20
> >=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
>=20
>=20