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

[Christophe Leroy]

Le 19/01/2023 à 10:53, Michal Suchanek a écrit :
> 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 at suse.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];

Can you declare that in the for block where it is used instead ?

> +		char *of_display_format = "of-display.%d";

Should be const ?

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


Can you make buf big enough to avoid that ?

And by the way could it be called something else than 'buf' ?

See exemple here : 
https://elixir.bootlin.com/linux/v6.1/source/drivers/fsi/fsi-occ.c#L690


> +			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;
>   			of_platform_device_create(node, buf, NULL);