linux-kernel - Re: [PATCH v4 14/14] of: Improve __of_add_property

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Message-ID: <20250110204154.GA3529721-robh@kernel.org>
Date: Fri, 10 Jan 2025 14:41:54 -0600
From: Rob Herring <robh@...nel.org>
To: Zijun Hu <zijun_hu@...oud.com>
Cc: Saravana Kannan <saravanak@...gle.com>,
	Maxime Ripard <mripard@...nel.org>,
	Robin Murphy <robin.murphy@....com>,
	Grant Likely <grant.likely@...retlab.ca>,
	Marc Zyngier <maz@...nel.org>,
	Andreas Herrmann <andreas.herrmann@...xeda.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Catalin Marinas <catalin.marinas@....com>,
	Mike Rapoport <rppt@...nel.org>,
	Oreoluwa Babatunde <quic_obabatun@...cinc.com>,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	Zijun Hu <quic_zijuhu@...cinc.com>
Subject: Re: [PATCH v4 14/14] of: Improve __of_add_property_sysfs()
 readability

On Thu, Jan 09, 2025 at 09:27:05PM +0800, Zijun Hu wrote:
> From: Zijun Hu <quic_zijuhu@...cinc.com>
> 
> __of_add_property_sysfs() hard codes string "security-" length as 9, but
> that is not obvious for readers.
> 
> Improve its readability by using strlen().

Does the compiler optimize the strlen call away? Maybe, maybe not. If 
not, that's N calls to strlen() where N is the number of properties in 
your DT. That's in the 1000s easily.

Do you really want to go test enough compiler versions we support to 
feel confident this is optimized away. I don't.

Rob

> 
> Signed-off-by: Zijun Hu <quic_zijuhu@...cinc.com>
> ---
>  drivers/of/kobj.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/of/kobj.c b/drivers/of/kobj.c
> index aa887166f0d21030d620d43c864ca76cde1c6d05..44bfe50c6ea6503e3940578de1dfc7fe0583dfb3 100644
> --- a/drivers/of/kobj.c
> +++ b/drivers/of/kobj.c
> @@ -62,10 +62,11 @@ static const char *safe_name(const struct kobject *kobj, const char *orig_name)
>  
>  int __of_add_property_sysfs(struct device_node *np, struct property *pp)
>  {
> +	const char *security_prefix = "security-";
>  	int rc;
>  
>  	/* Important: Don't leak passwords */
> -	bool secure = strncmp(pp->name, "security-", 9) == 0;
> +	bool secure = strncmp(pp->name, security_prefix, strlen(security_prefix)) == 0;
>  
>  	if (!IS_ENABLED(CONFIG_SYSFS))
>  		return 0;
> 
> -- 
> 2.34.1
>