linux-kernel - Re: [PATCH v2][next] tty: sunsu: Simplify device_node cleanup by using _

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Date: Thu, 2 May 2024 22:21:16 +0530
From: Shresth Prasad <shresthprasad7@...il.com>
To: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Cc: davem@...emloft.net, gregkh@...uxfoundation.org, jirislaby@...nel.org, 
	sparclinux@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-serial@...r.kernel.org, javier.carrasco.cruz@...il.com, 
	skhan@...uxfoundation.org, Julia Lawall <julia.lawall@...ia.fr>
Subject: Re: [PATCH v2][next] tty: sunsu: Simplify device_node cleanup by
 using __free

On Thu, May 2, 2024 at 9:35 PM Ilpo Järvinen
<ilpo.jarvinen@...ux.intel.com> wrote:
>
> On Wed, 1 May 2024, Shresth Prasad wrote:
>
> > Add `__free` function attribute to `ap` and `match` pointer
> > initialisations which ensure that the pointers are freed as soon as they
> > go out of scope, thus removing the need to manually free them using
> > `of_node_put`.
> >
> > This also removes the need for the `goto` statement and the `rc`
> > variable.
> >
> > Tested using a qemu x86_64 virtual machine.
>
> Eh, how can you test this with an x86_64 VM ???
>
> config SERIAL_SUNSU
>         tristate "Sun SU serial support"
>         depends on SPARC && PCI
>

By that, I mean that I compiled the kernel and ran the produced bzImage
on a x86_64 qemu machine.
I unfortunately don't have the hardware to test it on, but I don't
think the change is complex enough to require testing on real hardware
(unless I'm assuming incorrectly).

Regards,
Shresth

> > Suggested-by: Julia Lawall <julia.lawall@...ia.fr>
> > Signed-off-by: Shresth Prasad <shresthprasad7@...il.com>
> > ---
> > Changes in v2:
> >     - Specify how the patch was tested
> >
> >  drivers/tty/serial/sunsu.c | 37 +++++++++++--------------------------
> >  1 file changed, 11 insertions(+), 26 deletions(-)
> >
> > diff --git a/drivers/tty/serial/sunsu.c b/drivers/tty/serial/sunsu.c
> > index 67a5fc70bb4b..0f463da5e7ce 100644
> > --- a/drivers/tty/serial/sunsu.c
> > +++ b/drivers/tty/serial/sunsu.c
> > @@ -1382,44 +1382,29 @@ static inline struct console *SUNSU_CONSOLE(void)
> >
> >  static enum su_type su_get_type(struct device_node *dp)
> >  {
> > -     struct device_node *ap = of_find_node_by_path("/aliases");
> > -     enum su_type rc = SU_PORT_PORT;
> > +     struct device_node *ap __free(device_node) =
> > +                         of_find_node_by_path("/aliases");
> >
> >       if (ap) {
> >               const char *keyb = of_get_property(ap, "keyboard", NULL);
> >               const char *ms = of_get_property(ap, "mouse", NULL);
> > -             struct device_node *match;
> >
> >               if (keyb) {
> > -                     match = of_find_node_by_path(keyb);
> > +                     struct device_node *match __free(device_node) =
> > +                                         of_find_node_by_path(keyb);
> >
> > -                     /*
> > -                      * The pointer is used as an identifier not
> > -                      * as a pointer, we can drop the refcount on
> > -                      * the of__node immediately after getting it.
> > -                      */
> > -                     of_node_put(match);
> > -
> > -                     if (dp == match) {
> > -                             rc = SU_PORT_KBD;
> > -                             goto out;
> > -                     }
> > +                     if (dp == match)
> > +                             return SU_PORT_KBD;
> >               }
> >               if (ms) {
> > -                     match = of_find_node_by_path(ms);
> > +                     struct device_node *match __free(device_node) =
> > +                                         of_find_node_by_path(ms);
> >
> > -                     of_node_put(match);
> > -
> > -                     if (dp == match) {
> > -                             rc = SU_PORT_MS;
> > -                             goto out;
> > -                     }
> > +                     if (dp == match)
> > +                             return SU_PORT_MS;
> >               }
> >       }
> > -
> > -out:
> > -     of_node_put(ap);
> > -     return rc;
> > +     return SU_PORT_PORT;
> >  }
> >
> >  static int su_probe(struct platform_device *op)
> >