Re: [PATCH] libfdt: Fix fdt_appendprop_addrrange documentation

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On Thu, Aug 31, 2023 at 01:39:18PM +0100, Pierre-Clément Tosi wrote:
> According to the documentation, the function should default to the very
> common property name <reg> when none is "specified". However, neither
> passing NULL (ends up calling strlen(NULL) and segfaults) nor ""
> (appends a property with an empty name) implements this behavior.
> Furthermore, the test case supposed to cover this default value actually
> passes the value to the function, somewhat defeating its own purpose:
>     /* 2. default property name */
>     // ...
>     err = fdt_appendprop_addrrange(fdt, 0, offset, "reg", addr, size);
>     if (err)
>             FAIL("Failed to set \"reg\": %s", fdt_strerror(err));
>     check_getprop_addrrange(fdt, 0, offset, "reg", 1);
> Finally, nothing in the implementation of the function seems to attempt
> to cover that use-case.
> As the feature can't ever have been used by clients and as the resulting
> reduced readability of the caller seems (IMO) to outweigh any potential
> benefit this API would bring, remove the erroneous documentation instead
> of trying to fix the function.
> Reported-by: Mostafa Saleh <smostafa@xxxxxxxxxx>
> Signed-off-by: Pierre-Clément Tosi <ptosi@xxxxxxxxxx>

Nice catch, and an excellent commit message.

I don't recall this specifically, but my guess would be that an
original draft included that behaviour, but I nixed it during review,
but then both the submitted and I forgot to update the documentation
comments as well.


> ---
>  libfdt/libfdt.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> diff --git a/libfdt/libfdt.h b/libfdt/libfdt.h
> index 2a4f32c..0677fea 100644
> --- a/libfdt/libfdt.h
> +++ b/libfdt/libfdt.h
> @@ -2029,7 +2029,7 @@ static inline int fdt_appendprop_cell(void *fdt, int nodeoffset,
>   * address and size) to the value of the named property in the given
>   * node, or creates a new property with that value if it does not
>   * already exist.
> - * If "name" is not specified, a default "reg" is used.
> + *
>   * Cell sizes are determined by parent's #address-cells and #size-cells.
>   *
>   * This function may insert data into the blob, and will therefore

David Gibson			| I'll have my music baroque, and my code
david AT	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!

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