linux-kernel - Re: [PATCH] hwmon: Remove checks for validity of dev

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Message-ID: <6c0335ca-eb16-b4de-1f2c-8bdc82219b57@roeck-us.net>
Date:   Fri, 28 Jan 2022 07:05:00 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     Muhammad Usama Anjum <usama.anjum@...labora.com>,
        Jean Delvare <jdelvare@...e.com>
Cc:     kernel@...labora.com, kernel-janitors@...r.kernel.org,
        linux-hwmon@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] hwmon: Remove checks for validity of dev

On 1/28/22 04:59, Muhammad Usama Anjum wrote:
> dev is being dereferenced in device_property_present() which means that
> it is valid. Don't check its validity again and simplify the code.
> 
> Signed-off-by: Muhammad Usama Anjum <usama.anjum@...labora.com>
> ---
>   drivers/hwmon/hwmon.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/hwmon/hwmon.c b/drivers/hwmon/hwmon.c
> index e36ea82da1474..aec32abd0a89f 100644
> --- a/drivers/hwmon/hwmon.c
> +++ b/drivers/hwmon/hwmon.c
> @@ -822,7 +822,7 @@ __hwmon_device_register(struct device *dev, const char *name, void *drvdata,
>   	hwdev->name = name;
>   	hdev->class = &hwmon_class;
>   	hdev->parent = dev;
> -	hdev->of_node = dev ? dev->of_node : NULL;
> +	hdev->of_node = dev->of_node;
>   	hwdev->chip = chip;
>   	dev_set_drvdata(hdev, drvdata);
>   	dev_set_name(hdev, HWMON_ID_FORMAT, id);
> @@ -834,7 +834,7 @@ __hwmon_device_register(struct device *dev, const char *name, void *drvdata,
>   
>   	INIT_LIST_HEAD(&hwdev->tzdata);
>   
> -	if (dev && dev->of_node && chip && chip->ops->read &&
> +	if (dev->of_node && chip && chip->ops->read &&
>   	    chip->info[0]->type == hwmon_chip &&
>   	    (chip->info[0]->config[0] & HWMON_C_REGISTER_TZ)) {
>   		err = hwmon_thermal_register_sensors(hdev);

Wrong fix, sorry. While I would love to make dev mandatory, the function
is called with dev == NULL from at least one place, and the check is (still)
needed. Even if/when it is removed we would have to add an early check
and return -EINVAL if it is NULL.

Guenter