Re: [PATCH] of: implement of_prepend_property

[Sascha Hauer <sha@pengutronix.de>]

On Fri, Sep 09, 2022 at 09:40:50AM +0200, Ahmad Fatoum wrote:
> Like of_append_property for adding at the end of properties, implement
> of_prepend_property for placing data into the front.
> 
> This is especially useful to fixup most-specific compatibles into
> existing nodes.
> 
> Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
> ---
>  drivers/of/base.c           | 35 +++++++++++++++++++++++++++++++++++
>  include/of.h                |  8 ++++++++
>  test/self/of_manipulation.c |  2 +-
>  3 files changed, 44 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/of/base.c b/drivers/of/base.c
> index 212b226eb55c..e208949b08bd 100644
> --- a/drivers/of/base.c
> +++ b/drivers/of/base.c
> @@ -2378,6 +2378,41 @@ int of_append_property(struct device_node *np, const char *name, const void *val
>  	return 0;
>  }
>  
> +int of_prepend_property(struct device_node *np, const char *name, const void *val, int len)
> +{
> +	struct property *pp;
> +	int orig_len;
> +	const void *orig_buf;
> +	void *buf;
> +
> +	if (!np)
> +		return -ENOENT;
> +
> +	pp = of_find_property(np, name, NULL);
> +	if (!pp) {
> +		of_new_property(np, name, val, len);
> +		return 0;
> +	}
> +
> +	orig_len = pp->length;
> +	buf = realloc(pp->value, orig_len + len);
> +	if (!buf)
> +		return -ENOMEM;
> +
> +	orig_buf = pp->value_const ?: buf;
> +	if (orig_buf) {

orig_buf is always non NULL here.

> +		memmove(buf + len, orig_buf, orig_len);
> +		pp->value_const = NULL;
> +	}
> +
> +	memcpy(buf, val, len);
> +
> +	pp->value = buf;
> +	pp->length += len;
> +
> +	return 0;
> +}

How about a bit more straight forward variant like this:

int of_prepend_property(struct device_node *np, const char *name, const void *val, int len)
{
	struct property *pp;
	int oldlen = 0;

	pp = of_find_property(np, name, &oldlen);
	if (!pp) {
		of_new_property(np, name, val, len);
		return 0;
	}

	oldval = of_property_get_value(pp);

	buf = malloc(len + oldlen);
	if (!buf)
		return -ENOMEM;

	memcpy(buf, val, len);
	memcpy(buf + len, oldval, oldlen);

	free(pp->value);
	pp->value = buf;
	pp->length = len + oldlen;
	pp->value_const = NULL;

	return 0;
}

Sascha

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