linux-kernel - Re: [PATCH] driver core: auxiliary bus: Optimize auxiliary_match

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Message-ID: <2025090222-darn-tweet-739c@gregkh>
Date: Tue, 2 Sep 2025 14:20:14 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: Zijun Hu <zijun_hu@...oud.com>
Cc: Dave Ertman <david.m.ertman@...el.com>, Ira Weiny <ira.weiny@...el.com>,
	Leon Romanovsky <leon@...nel.org>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Danilo Krummrich <dakr@...nel.org>, linux-kernel@...r.kernel.org,
	Zijun Hu <zijun.hu@....qualcomm.com>
Subject: Re: [PATCH] driver core: auxiliary bus: Optimize auxiliary_match_id()

On Tue, Sep 02, 2025 at 08:05:32PM +0800, Zijun Hu wrote:
> From: Zijun Hu <zijun.hu@....qualcomm.com>
> 
> Variable @match_size is fixed in auxiliary_match_id().
> 
> Optimize the function by moving the logic calculating the variable
> out of the for loop.

Optimize it how?  Does this actually result in a difference somehow, if
so, what?

Please be specific.

> Signed-off-by: Zijun Hu <zijun.hu@....qualcomm.com>
> ---
>  drivers/base/auxiliary.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/base/auxiliary.c b/drivers/base/auxiliary.c
> index 12ffdd8437567f282374bbf3775d9de7ca0dc4c7..9a53ada043045031e565ade57fd7ba781e7d20ea 100644
> --- a/drivers/base/auxiliary.c
> +++ b/drivers/base/auxiliary.c
> @@ -171,14 +171,14 @@
>  static const struct auxiliary_device_id *auxiliary_match_id(const struct auxiliary_device_id *id,
>  							    const struct auxiliary_device *auxdev)
>  {
> -	for (; id->name[0]; id++) {
> -		const char *p = strrchr(dev_name(&auxdev->dev), '.');
> -		int match_size;
> +	const char *p = strrchr(dev_name(&auxdev->dev), '.');
> +	int match_size;
>  
> -		if (!p)
> -			continue;
> -		match_size = p - dev_name(&auxdev->dev);
> +	if (!p)
> +		return NULL;
> +	match_size = p - dev_name(&auxdev->dev);
>  
> +	for (; id->name[0]; id++) {
>  		/* use dev_name(&auxdev->dev) prefix before last '.' char to match to */
>  		if (strlen(id->name) == match_size &&
>  		    !strncmp(dev_name(&auxdev->dev), id->name, match_size))
> 

thanks,

greg k-h