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Date: Fri, 31 May 2024 17:44:05 +0100
From: Lee Jones <lee@kernel.org>
To: MarileneGarcia <marilene.agarcia@gmail.com>
Cc: Pavel Machek <pavel@ucw.cz>, Michael Ellerman <mpe@ellerman.id.au>,
	Nicholas Piggin <npiggin@gmail.com>,
	Christophe Leroy <christophe.leroy@csgroup.eu>,
	"Naveen N. Rao" <naveen.n.rao@linux.ibm.com>,
	Julia Lawall <julia.lawall@inria.fr>,
	Shuah Khan <skhan@linuxfoundation.org>,
	Javier Carrasco <javier.carrasco.cruz@gmail.com>,
	linux-leds@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 linux-next] leds: powernv: replace of_node_put to
 __free
Message-ID: <20240531164405.GV1005600@google.com>
References: <20240529200233.1188228-1-marilene.agarcia@gmail.com>
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In-Reply-To: <20240529200233.1188228-1-marilene.agarcia@gmail.com>

On Wed, 29 May 2024, MarileneGarcia wrote:

> Use __free for device_node values, and thus drop calls to
> of_node_put.
> 
> The variable attribute __free adds a scope based cleanup to
> the device node. The goal is to reduce memory management issues
> in the kernel code.
> 
> The of_node_put calls were removed, and the
> for_each_available_child_of_node was replaced to the equivalent
> for_each_available_child_of_node_scoped which use the __free.
> 
> Suggested-by: Julia Lawall <julia.lawall@inria.fr>
> Signed-off-by: MarileneGarcia <marilene.agarcia@gmail.com>
> ---
> Changes v2:
> It was missing a blank line.
> 
> Suggested-by: Julia Lawall <julia.lawall@inria.fr>
> Signed-off-by: MarileneGarcia <marilene.agarcia@gmail.com>
> ---
>  drivers/leds/leds-powernv.c | 28 +++++++++-------------------
>  1 file changed, 9 insertions(+), 19 deletions(-)
> 
> diff --git a/drivers/leds/leds-powernv.c b/drivers/leds/leds-powernv.c
> index 4f01acb75727..8f94d2efed9f 100644
> --- a/drivers/leds/leds-powernv.c
> +++ b/drivers/leds/leds-powernv.c
> @@ -246,29 +246,25 @@ static int powernv_led_classdev(struct platform_device *pdev,
>  	const char *cur = NULL;
>  	int rc = -1;
>  	struct property *p;
> -	struct device_node *np;
>  	struct powernv_led_data *powernv_led;
>  	struct device *dev = &pdev->dev;
>  
> -	for_each_available_child_of_node(led_node, np) {
> +	for_each_available_child_of_node_scoped(led_node, np) {
>  		p = of_find_property(np, "led-types", NULL);
>  
>  		while ((cur = of_prop_next_string(p, cur)) != NULL) {
>  			powernv_led = devm_kzalloc(dev, sizeof(*powernv_led),
>  						   GFP_KERNEL);
> -			if (!powernv_led) {
> -				of_node_put(np);
> +			if (!powernv_led)
>  				return -ENOMEM;
> -			}
>  
>  			powernv_led->common = powernv_led_common;
>  			powernv_led->loc_code = (char *)np->name;
>  
>  			rc = powernv_led_create(dev, powernv_led, cur);
> -			if (rc) {
> -				of_node_put(np);
> +			if (rc)
>  				return rc;
> -			}
> +
>  		} /* while end */
>  	}
>  
> @@ -278,12 +274,11 @@ static int powernv_led_classdev(struct platform_device *pdev,
>  /* Platform driver probe */
>  static int powernv_led_probe(struct platform_device *pdev)
>  {
> -	struct device_node *led_node;
>  	struct powernv_led_common *powernv_led_common;
>  	struct device *dev = &pdev->dev;
> -	int rc;
> +	struct device_node *led_node __free(device_node) =
> +							of_find_node_by_path("/ibm,opal/leds");

This is not a good line-break strategy.

	struct device_node *led_node
		__free(device_node) = of_find_node_by_path("/ibm,opal/leds");

	struct device_node *led_node __free(device_node) =
		of_find_node_by_path("/ibm,opal/leds");

Please choose one of these instead.

I suggest the top one might read a little easier.

> -	led_node = of_find_node_by_path("/ibm,opal/leds");

Does the __free() have to be combined with an allocation?

>  	if (!led_node) {
>  		dev_err(dev, "%s: LED parent device node not found\n",
>  			__func__);
> @@ -292,20 +287,15 @@ static int powernv_led_probe(struct platform_device *pdev)
>  
>  	powernv_led_common = devm_kzalloc(dev, sizeof(*powernv_led_common),
>  					  GFP_KERNEL);
> -	if (!powernv_led_common) {
> -		rc = -ENOMEM;
> -		goto out;
> -	}
> +	if (!powernv_led_common)
> +		return -ENOMEM;
>  
>  	mutex_init(&powernv_led_common->lock);
>  	powernv_led_common->max_led_type = cpu_to_be64(OPAL_SLOT_LED_TYPE_MAX);
>  
>  	platform_set_drvdata(pdev, powernv_led_common);
>  
> -	rc = powernv_led_classdev(pdev, led_node, powernv_led_common);
> -out:
> -	of_node_put(led_node);
> -	return rc;
> +	return powernv_led_classdev(pdev, led_node, powernv_led_common);
>  }
>  
>  /* Platform driver remove */
> -- 
> 2.34.1
> 

-- 
Lee Jones [李琼斯]