linux-kernel - Re: [PATCH v2] of: Fix of platform build on powerpc due to bad of disaply code

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Message-ID: <20230120175253.GW16547@kitsune.suse.cz>
Date:   Fri, 20 Jan 2023 18:52:53 +0100
From:   Michal Suchánek <msuchanek@...e.de>
To:     Rob Herring <robh+dt@...nel.org>
Cc:     "Erhard F." <erhard_f@...lbox.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE" 
        <devicetree@...r.kernel.org>, linuxppc-dev@...ts.ozlabs.org,
        Javier Martinez Canillas <javierm@...hat.com>,
        open list <linux-kernel@...r.kernel.org>,
        Frank Rowand <frowand.list@...il.com>
Subject: Re: [PATCH v2] of: Fix of platform build on powerpc due to bad of
 disaply code

Hello,

On Fri, Jan 20, 2023 at 11:23:39AM -0600, Rob Herring wrote:
> On Thu, Jan 19, 2023 at 3:53 AM Michal Suchanek <msuchanek@...e.de> wrote:
> >
> > The commit 2d681d6a23a1 ("of: Make of framebuffer devices unique")
> > breaks build because of wrong argument to snprintf. That certainly
> > avoids the runtime error but is not the intended outcome.
> >
> > Also use standard device name format of-display.N for all created
> > devices.
> >
> > Fixes: 2d681d6a23a1 ("of: Make of framebuffer devices unique")
> > Signed-off-by: Michal Suchanek <msuchanek@...e.de>
> > ---
> > v2: Update the device name format
> > ---
> >  drivers/of/platform.c | 12 ++++++++----
> >  1 file changed, 8 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/of/platform.c b/drivers/of/platform.c
> > index f2a5d679a324..8c1b1de22036 100644
> > --- a/drivers/of/platform.c
> > +++ b/drivers/of/platform.c
> > @@ -525,7 +525,9 @@ static int __init of_platform_default_populate_init(void)
> >         if (IS_ENABLED(CONFIG_PPC)) {
> >                 struct device_node *boot_display = NULL;
> >                 struct platform_device *dev;
> > -               int display_number = 1;
> > +               int display_number = 0;
> > +               char buf[14];
> > +               char *of_display_format = "of-display.%d";
> 
> static const as suggested and can we just move on please...
Only const, static could be dodgy

> >                 int ret;
> >
> >                 /* Check if we have a MacOS display without a node spec */
> > @@ -556,7 +558,10 @@ static int __init of_platform_default_populate_init(void)
> >                         if (!of_get_property(node, "linux,opened", NULL) ||
> >                             !of_get_property(node, "linux,boot-display", NULL))
> >                                 continue;
> > -                       dev = of_platform_device_create(node, "of-display", NULL);
> > +                       ret = snprintf(buf, sizeof(buf), of_display_format, display_number++);
> 
> The boot display is always "of-display.0". Just use the fixed string
> here. Then we can get rid of the whole debate around static const.

I prefer to use the same format string when the names should be
consistent. Also it would resurrect the starting from 1 debate.

But if you really want to have two strings I do not care all that much.

> 
> > +                       if (ret >= sizeof(buf))
> > +                               continue;
> 
> This only happens if display_number becomes too big. Why continue on?
> The next iteration will fail too.

Yes, there is no need to continue with the loop.

Thanks

Michal

> 
> > +                       dev = of_platform_device_create(node, buf, NULL);
> >                         if (WARN_ON(!dev))
> >                                 return -ENOMEM;
> >                         boot_display = node;
> > @@ -564,10 +569,9 @@ static int __init of_platform_default_populate_init(void)
> >                 }
> >
> >                 for_each_node_by_type(node, "display") {
> > -                       char *buf[14];
> >                         if (!of_get_property(node, "linux,opened", NULL) || node == boot_display)
> >                                 continue;
> > -                       ret = snprintf(buf, "of-display-%d", display_number++);
> > +                       ret = snprintf(buf, sizeof(buf), of_display_format, display_number++);
> >                         if (ret >= sizeof(buf))
> >                                 continue;
> 
> Here too in the original change.
> 
> >                         of_platform_device_create(node, buf, NULL);
> > --
> > 2.35.3
> >