linux-kernel - Re: [PATCH v3] powerpc:85xx: Add missing of_node_put() in sgy

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Date:   Fri, 17 Jun 2022 07:37:12 +0200
From:   Christophe JAILLET <christophe.jaillet@...adoo.fr>
To:     Liang He <windhl@....com>, oss@...error.net, mpe@...erman.id.au,
        benh@...nel.crashing.org, paulus@...ba.org,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] powerpc:85xx: Add missing of_node_put() in sgy_cst1000

Le 17/06/2022 à 07:22, Liang He a écrit :
> In gpio_halt_probe(), of_find_matching_node() will return a node
> pointer with refcount incremented. We should use of_node_put() in
> fail path or when it is not used anymore.
> 
> Signed-off-by: Liang He <windhl@....com>
> ---
>   arch/powerpc/platforms/85xx/sgy_cts1000.c | 39 +++++++++++++++--------
>   1 file changed, 25 insertions(+), 14 deletions(-)
> 
> diff --git a/arch/powerpc/platforms/85xx/sgy_cts1000.c b/arch/powerpc/platforms/85xx/sgy_cts1000.c
> index 98ae64075193..a8690fc552cf 100644
> --- a/arch/powerpc/platforms/85xx/sgy_cts1000.c
> +++ b/arch/powerpc/platforms/85xx/sgy_cts1000.c
> @@ -71,33 +71,39 @@ static int gpio_halt_probe(struct platform_device *pdev)
>   {
>   	enum of_gpio_flags flags;
>   	struct device_node *node = pdev->dev.of_node;
> +	struct device_node *child_node;
>   	int gpio, err, irq;
>   	int trigger;
> +	int ret;
>   
>   	if (!node)
>   		return -ENODEV;
>   
>   	/* If there's no matching child, this isn't really an error */
> -	halt_node = of_find_matching_node(node, child_match);
> -	if (!halt_node)
> +	child_node = of_find_matching_node(node, child_match);
> +	if (!child_node)
>   		return 0;
>   
>   	/* Technically we could just read the first one, but punish
>   	 * DT writers for invalid form. */
> -	if (of_gpio_count(halt_node) != 1)
> -		return -EINVAL;
> +	if (of_gpio_count(child_node) != 1) {
> +		ret = -EINVAL;
> +		goto err_put;
> +	}
>   
>   	/* Get the gpio number relative to the dynamic base. */
> -	gpio = of_get_gpio_flags(halt_node, 0, &flags);
> -	if (!gpio_is_valid(gpio))
> -		return -EINVAL;
> +	gpio = of_get_gpio_flags(child_node, 0, &flags);
> +	if (!gpio_is_valid(gpio)) {
> +		ret = -EINVAL;
> +		gotot err_put;
> +	}
>   
>   	err = gpio_request(gpio, "gpio-halt");
>   	if (err) {
>   		printk(KERN_ERR "gpio-halt: error requesting GPIO %d.\n",
>   		       gpio);
> -		halt_node = NULL;
> -		return err;
> +		ret = err;

Sorry for not seeing and asking before, but why do you need 'ret'?
Can't you use the existing 'err' in place in this whole patch?

> +		goto err_put;
>   	}
>   
>   	trigger = (flags == OF_GPIO_ACTIVE_LOW);
> @@ -105,15 +111,15 @@ static int gpio_halt_probe(struct platform_device *pdev)
>   	gpio_direction_output(gpio, !trigger);
>   
>   	/* Now get the IRQ which tells us when the power button is hit */
> -	irq = irq_of_parse_and_map(halt_node, 0);
> +	irq = irq_of_parse_and_map(child_node, 0);
>   	err = request_irq(irq, gpio_halt_irq, IRQF_TRIGGER_RISING |
> -			  IRQF_TRIGGER_FALLING, "gpio-halt", halt_node);
> +			  IRQF_TRIGGER_FALLING, "gpio-halt", child_node);
>   	if (err) {
>   		printk(KERN_ERR "gpio-halt: error requesting IRQ %d for "
>   		       "GPIO %d.\n", irq, gpio);
>   		gpio_free(gpio);
> -		halt_node = NULL;
> -		return err;
> +		ret = err;
> +		goto err_put;
>   	}
>   
>   	/* Register our halt function */
> @@ -122,8 +128,12 @@ static int gpio_halt_probe(struct platform_device *pdev)
>   
>   	printk(KERN_INFO "gpio-halt: registered GPIO %d (%d trigger, %d"
>   	       " irq).\n", gpio, trigger, irq);
> +	ret = 0;
> +	halt_node = of_node_get(child_node);

LGTM, but my preferred style would be:
	halt_node = child_node;
	return 0;

I'm not a maintainer, so this is just my opinion and it is mostly a 
mater of taste.

CJ

>   
> -	return 0;
> +err_put:
> +	of_node_put(child_node);
> +	return ret;
>   }
>   
>   static int gpio_halt_remove(struct platform_device *pdev)
> @@ -139,6 +149,7 @@ static int gpio_halt_remove(struct platform_device *pdev)
>   
>   		gpio_free(gpio);
>   
> +		of_node_put(halt_node);
>   		halt_node = NULL;
>   	}
>