linux-kernel - Re: [PATCH 3/3] of: Use scope based of_node

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Message-ID: <CAL_JsqK4QpFmLi0WVG0Vpxv82Y1eWxbGS7ESWBhPoKg+WFV5Tw@mail.gmail.com>
Date: Fri, 5 Apr 2024 08:00:51 -0500
From: Rob Herring <robh@...nel.org>
To: Saravana Kannan <saravanak@...gle.com>
Cc: Jonathan Cameron <jic23@...nel.org>, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] of: Use scope based of_node_put() cleanups

On Thu, Apr 4, 2024 at 6:22 PM Saravana Kannan <saravanak@...gle.com> wrote:
>
> On Thu, Apr 4, 2024 at 7:15 AM Rob Herring <robh@...nel.org> wrote:
> >
> > Use the relatively new scope based of_node_put() cleanup to simplify
> > function exit handling. Doing so reduces the chances of forgetting an
> > of_node_put() and simplifies error paths by avoiding the need for goto
> > statements.
> >
> > Signed-off-by: Rob Herring <robh@...nel.org>
> > ---
> >  drivers/of/address.c  | 60 ++++++++++++++++-----------------------------------
> >  drivers/of/property.c | 22 ++++++-------------
> >  2 files changed, 26 insertions(+), 56 deletions(-)
> >
> > diff --git a/drivers/of/address.c b/drivers/of/address.c
> > index ae46a3605904..f7b2d535a6d1 100644
> > --- a/drivers/of/address.c
> > +++ b/drivers/of/address.c
> > @@ -491,7 +491,6 @@ static u64 __of_translate_address(struct device_node *dev,
> >                                   const __be32 *in_addr, const char *rprop,
> >                                   struct device_node **host)
> >  {
> > -       struct device_node *parent = NULL;
> >         struct of_bus *bus, *pbus;
> >         __be32 addr[OF_MAX_ADDR_CELLS];
> >         int na, ns, pna, pns;
> > @@ -504,7 +503,7 @@ static u64 __of_translate_address(struct device_node *dev,
> >
> >         *host = NULL;
> >         /* Get parent & match bus type */
> > -       parent = get_parent(dev);
> > +       struct device_node *parent __free(device_node) = get_parent(dev);
>
> Can we leave the variable definition where it was? We generally define
> all the variables up top. So, defining the one variable in the middle
> feels weird. I at least get when we do this inside for/if blocks. But
> randomly in the middle feels weird.

There's an 'of_node_get(dev);' before this. Ordering wise, we need to
hold the ref on the child before we get its parent. I suppose I can
also convert that to use the cleanups. I'll have to add another local
ptr to do that though.

>
> Similar comments in other places. Since both kfree() and of_put() can
> both handle NULL pointers, I'd be surprised if we HAVE to combine
> these lines.

https://lore.kernel.org/all/CAHk-=wgRHiV5VSxtfXA4S6aLUmcQYEuB67u3BJPJPtuESs1JyA@mail.gmail.com/