Re: [PATCH] fdt_get_phandle: Return invalid phandles as 0

[David Gibson <david-xT8FGy+AXnRB3Ne2BGzF6laj5H9X9Tb+@public.gmane.org>]

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On Mon, Aug 01, 2022 at 01:31:34PM +0100, Pierre-Clément Tosi wrote:
> If a tree contains an invalid <u32> value as its <phandle> property,
> mask it with '0' (invalid value) instead of returning it from
> fdt_get_phandle().
> 
> Signed-off-by: Pierre-Clément Tosi <ptosi-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>

Hm.. I don't really see the point of this.  Because FDT_MAX_PHANDLE is
0xfffffffe (-2), the only effect this has is to change 0xffffffff (-1)
into 0 when returned.  Both are, indeed, invalid phandles, but they're
sometimes used to mean slightly different things in incomplete trees,
so it seems more useful to return these separately

> ---
>  libfdt/fdt_ro.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/libfdt/fdt_ro.c b/libfdt/fdt_ro.c
> index 9f6c551..7d1da6d 100644
> --- a/libfdt/fdt_ro.c
> +++ b/libfdt/fdt_ro.c
> @@ -507,6 +507,7 @@ const void *fdt_getprop(const void *fdt, int nodeoffset,
>  
>  uint32_t fdt_get_phandle(const void *fdt, int nodeoffset)
>  {
> +	uint32_t phandle;
>  	const fdt32_t *php;
>  	int len;
>  
> @@ -519,7 +520,11 @@ uint32_t fdt_get_phandle(const void *fdt, int nodeoffset)
>  			return 0;
>  	}
>  
> -	return fdt32_ld_(php);
> +	phandle = fdt32_ld_(php);
> +	if (phandle > (uint32_t)FDT_MAX_PHANDLE)
> +		phandle = 0;
> +
> +	return phandle;
>  }
>  
>  const char *fdt_get_alias_namelen(const void *fdt,

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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