Re: [PATCH] Add a libfdt function to write a property placeholder

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

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On Sun, Mar 06, 2016 at 07:52:52PM -0700, Simon Glass wrote:
> The existing function to add a new property to a tree being built requires
> that the entire contents of the new property be passed in. For some
> applications it is more convenient to be able to add the property contents
> later, perhaps by reading from a file. This avoids double-buffering of the
> contents.
> 
> Add a new function to support this and adjust the existing fdt_property() to
> use it.
> Signed-off-by: Simon Glass <sjg-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>

The change looks fine, but I'd like to see a testcase added for it.

> ---
> 
>  libfdt/fdt_sw.c | 16 ++++++++++++++--
>  libfdt/libfdt.h | 16 ++++++++++++++++
>  2 files changed, 30 insertions(+), 2 deletions(-)
> 
> diff --git a/libfdt/fdt_sw.c b/libfdt/fdt_sw.c
> index 6a80485..2bd15e7 100644
> --- a/libfdt/fdt_sw.c
> +++ b/libfdt/fdt_sw.c
> @@ -220,7 +220,7 @@ static int _fdt_find_add_string(void *fdt, const char *s)
>  	return offset;
>  }
>  
> -int fdt_property(void *fdt, const char *name, const void *val, int len)
> +int fdt_property_placeholder(void *fdt, const char *name, int len, void **valp)
>  {
>  	struct fdt_property *prop;
>  	int nameoff;
> @@ -238,7 +238,19 @@ int fdt_property(void *fdt, const char *name, const void *val, int len)
>  	prop->tag = cpu_to_fdt32(FDT_PROP);
>  	prop->nameoff = cpu_to_fdt32(nameoff);
>  	prop->len = cpu_to_fdt32(len);
> -	memcpy(prop->data, val, len);
> +	*valp = prop->data;
> +	return 0;
> +}
> +
> +int fdt_property(void *fdt, const char *name, const void *val, int len)
> +{
> +	void *ptr;
> +	int ret;
> +
> +	ret = fdt_property_placeholder(fdt, name, len, &ptr);
> +	if (ret)
> +		return ret;
> +	memcpy(ptr, val, len);
>  	return 0;
>  }
>  
> diff --git a/libfdt/libfdt.h b/libfdt/libfdt.h
> index 78adb12..d6a08b6 100644
> --- a/libfdt/libfdt.h
> +++ b/libfdt/libfdt.h
> @@ -1180,6 +1180,22 @@ static inline int fdt_property_cell(void *fdt, const char *name, uint32_t val)
>  {
>  	return fdt_property_u32(fdt, name, val);
>  }
> +
> +/**
> + * fdt_property_placeholder - add a new property and return a ptr to its value
> + *
> + * @fdt: pointer to the device tree blob
> + * @name: name of property to add
> + * @len: length of property value in bytes
> + * @valp: returns a pointer to where where the value should be placed
> + *
> + * returns:
> + *	0, on success
> + *	-FDT_ERR_BADMAGIC,
> + *	-FDT_ERR_NOSPACE, standard meanings
> + */
> +int fdt_property_placeholder(void *fdt, const char *name, int len, void **valp);
> +
>  #define fdt_property_string(fdt, name, str) \
>  	fdt_property(fdt, name, str, strlen(str)+1)
>  int fdt_end_node(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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