linux-kernel - Re: [PATCH v2] watchdog: tangox_wdt: test clock rate to avoid division by 0

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Date:	Thu, 3 Mar 2016 03:44:50 -0800
From:	Guenter Roeck <linux@...ck-us.net>
To:	Wolfram Sang <wsa@...-dreams.de>, linux-kernel@...r.kernel.org
Cc:	Wim Van Sebroeck <wim@...ana.be>, linux-watchdog@...r.kernel.org
Subject: Re: [PATCH v2] watchdog: tangox_wdt: test clock rate to avoid
 division by 0

On 03/03/2016 12:24 AM, Wolfram Sang wrote:
> From: Wolfram Sang <wsa+renesas@...g-engineering.com>
>
> The clk API may return 0 on clk_get_rate, so we should check the result before
> using it as a divisor. For this, refactor the code to use a central
> error path.
>
> Signed-off-by: Wolfram Sang <wsa+renesas@...g-engineering.com>

Reviewed-by: Guenter Roeck <linux@...ck-us.net>

> ---
>   drivers/watchdog/tangox_wdt.c | 14 ++++++++++----
>   1 file changed, 10 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/watchdog/tangox_wdt.c b/drivers/watchdog/tangox_wdt.c
> index 709c1ed6fd79b9..cfbed7e051b619 100644
> --- a/drivers/watchdog/tangox_wdt.c
> +++ b/drivers/watchdog/tangox_wdt.c
> @@ -139,6 +139,10 @@ static int tangox_wdt_probe(struct platform_device *pdev)
>   		return err;
>
>   	dev->clk_rate = clk_get_rate(dev->clk);
> +	if (!dev->clk_rate) {
> +		err = -EINVAL;
> +		goto err;
> +	}
>
>   	dev->wdt.parent = &pdev->dev;
>   	dev->wdt.info = &tangox_wdt_info;
> @@ -171,10 +175,8 @@ static int tangox_wdt_probe(struct platform_device *pdev)
>   	}
>
>   	err = watchdog_register_device(&dev->wdt);
> -	if (err) {
> -		clk_disable_unprepare(dev->clk);
> -		return err;
> -	}
> +	if (err)
> +		goto err;
>
>   	platform_set_drvdata(pdev, dev);
>
> @@ -187,6 +189,10 @@ static int tangox_wdt_probe(struct platform_device *pdev)
>   	dev_info(&pdev->dev, "SMP86xx/SMP87xx watchdog registered\n");
>
>   	return 0;
> +
> + err:
> +	clk_disable_unprepare(dev->clk);
> +	return err;
>   }
>
>   static int tangox_wdt_remove(struct platform_device *pdev)
>