linux-kernel - Re: [PATCH v2 01/16] watchdog: refactor watchdog_init

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Message-ID: <b65ae931-bfb3-acb4-8097-da4b81be1ea5@roeck-us.net>
Date:   Tue, 16 Apr 2019 06:23:08 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Wolfram Sang <wsa+renesas@...g-engineering.com>,
        linux-watchdog@...r.kernel.org
Cc:     linux-renesas-soc@...r.kernel.org,
        Wim Van Sebroeck <wim@...ux-watchdog.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 01/16] watchdog: refactor watchdog_init_timeout

On 4/16/19 3:25 AM, Wolfram Sang wrote:
> The function is not easy to read and has a problem: -EINVAL is returned
> when the module parameter is invalid but the DT parameter is OK.
> 
> Refactor the code to have the same pattern of checks for the module
> parameter and DT. Further ones can be easily added in the future if the
> need arises. The above mentioned problem is fixed, too.
> 
> Some documentation is added to describe the different handlings of '0'
> for the module parameter and the DT property.
> 
> Signed-off-by: Wolfram Sang <wsa+renesas@...g-engineering.com>

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

> ---
>   drivers/watchdog/watchdog_core.c | 33 +++++++++++++++++++--------------
>   1 file changed, 19 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/watchdog/watchdog_core.c b/drivers/watchdog/watchdog_core.c
> index eb8fa25f8eb2..21e53cc49977 100644
> --- a/drivers/watchdog/watchdog_core.c
> +++ b/drivers/watchdog/watchdog_core.c
> @@ -105,9 +105,12 @@ static void watchdog_check_min_max_timeout(struct watchdog_device *wdd)
>    * timeout module parameter (if it is valid value) or the timeout-sec property
>    * (only if it is a valid value and the timeout_parm is out of bounds).
>    * If none of them are valid then we keep the old value (which should normally
> - * be the default timeout value).
> + * be the default timeout value). Note that for the module parameter, '0' means
> + * 'use default' while it is an invalid value for the timeout-sec property.
> + * It should simply be dropped if you want to use the default value then.
>    *
> - * A zero is returned on success and -EINVAL for failure.
> + * A zero is returned on success or -EINVAL if all provided values are out of
> + * bounds.
>    */
>   int watchdog_init_timeout(struct watchdog_device *wdd,
>   				unsigned int timeout_parm, struct device *dev)
> @@ -117,22 +120,24 @@ int watchdog_init_timeout(struct watchdog_device *wdd,
>   
>   	watchdog_check_min_max_timeout(wdd);
>   
> -	/* try to get the timeout module parameter first */
> -	if (!watchdog_timeout_invalid(wdd, timeout_parm) && timeout_parm) {
> -		wdd->timeout = timeout_parm;
> -		return ret;
> -	}
> -	if (timeout_parm)
> +	/* check the driver supplied value (likely a module parameter) first */
> +	if (timeout_parm) {
> +		if (!watchdog_timeout_invalid(wdd, timeout_parm)) {
> +			wdd->timeout = timeout_parm;
> +			return 0;
> +		}
>   		ret = -EINVAL;
> +	}
>   
>   	/* try to get the timeout_sec property */
> -	if (dev == NULL || dev->of_node == NULL)
> -		return ret;
> -	of_property_read_u32(dev->of_node, "timeout-sec", &t);
> -	if (!watchdog_timeout_invalid(wdd, t) && t)
> -		wdd->timeout = t;
> -	else
> +	if (dev && dev->of_node &&
> +	    of_property_read_u32(dev->of_node, "timeout-sec", &t) == 0) {
> +		if (t && !watchdog_timeout_invalid(wdd, t)) {
> +			wdd->timeout = t;
> +			return 0;
> +		}
>   		ret = -EINVAL;
> +	}
>   
>   	return ret;
>   }
>