Re: [PATCH v4 1/6] device_tree: add qemu_fdt_setprop_strings() helper

[Andrew Jones]

On Tue, Aug 09, 2022 at 07:56:35PM +0100, Ben Dooks wrote:
> Add a helper to set a property from a set of strings
> to reduce the following code:
> 
>     static const char * const clint_compat[2] = {
>         "sifive,clint0", "riscv,clint0"
>     };
> 
>     qemu_fdt_setprop_string_array(fdt, nodename, "compatible",
>         (char **)&clint_compat, ARRAY_SIZE(clint_compat));
> 
> Signed-off-by: Ben Dooks <qemu@ben.fluff.org>
> ---
> v4:
>  - go back to the non-return call, no-one is using the result
> v3;
>  - fix return value for the call
>  - add better help text
> v2:
>  - fix node/path in comment
> ---
>  include/sysemu/device_tree.h | 19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
> 
> diff --git a/include/sysemu/device_tree.h b/include/sysemu/device_tree.h
> index ef060a9759..d5c05b5ebb 100644
> --- a/include/sysemu/device_tree.h
> +++ b/include/sysemu/device_tree.h
> @@ -87,6 +87,25 @@ int qemu_fdt_setprop_string(void *fdt, const char 
> *node_path,
>  int qemu_fdt_setprop_string_array(void *fdt, const char *node_path,
>                                    const char *prop, char **array, int len);
>  
> +/**
> + * qemu_fdt_setprop_strings: set a property from a set of strings
> + *
> + * @fdt: pointer to the dt blob
> + * @path: node name
> + * @prop: property array
> + *
> + * This is a helper for the qemu_fdt_setprop_string_array() function
> + * which takes a va-arg set of strings instead of having to setup a
> + * single use string array.
> + */
> +#define qemu_fdt_setprop_strings(fdt, path, prop, ...)          \
> +    do {                                                        \
> +        static const char * const __strs[] = { __VA_ARGS__ };   \

           ^^ We don't want that static there. That'll keep the storage
           for each invocation and require that __VA_ARGS__ are always
           constants only.

           I'd drop the const's too since __strs is only used for a
           single call where it immediately gets the const's cast'ed
           away.

> +        qemu_fdt_setprop_string_array(fdt, path, prop,          \
> +                (char **)&__strs, ARRAY_SIZE(__strs));          \

                   ^^ And then this can just be __strs

> +     } while(0)
> +
> +
>  int qemu_fdt_setprop_phandle(void *fdt, const char *node_path,
>                               const char *property,
>                               const char *target_node_path);
> -- 
> 2.35.1
> 
> 

Thanks,
drew