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

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Date:   Fri, 20 Jan 2023 11:23:39 -0600
From:   Rob Herring <robh+dt@...nel.org>
To:     Michal Suchanek <msuchanek@...e.de>
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

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...

>                 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.

> +                       if (ret >= sizeof(buf))
> +                               continue;

This only happens if display_number becomes too big. Why continue on?
The next iteration will fail too.

> +                       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
>