linux-kernel - Re: [PATCH v2 01/11] hwmon: (amc6821) Stop accepting invalid pwm values

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Message-ID: <42ab8d15-a195-42d4-a191-a25da00f4c8d@cherry.de>
Date: Wed, 3 Jul 2024 16:29:13 +0200
From: Quentin Schulz <quentin.schulz@...rry.de>
To: Guenter Roeck <linux@...ck-us.net>, linux-hwmon@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, Farouk Bouabid <farouk.bouabid@...rry.de>
Subject: Re: [PATCH v2 01/11] hwmon: (amc6821) Stop accepting invalid pwm
 values

Hi Guenter,

On 7/1/24 11:23 PM, Guenter Roeck wrote:
> The pwm value range is well defined from 0..255. Don't accept
> any values outside this range.
> 
> Signed-off-by: Guenter Roeck <linux@...ck-us.net>
> ---
> v2: Use kstrtou8() instead of kstrtol() where possible.
>      Limit range of pwm1_auto_point_pwm to 0..254 in patch 1
>      instead of limiting it later, and do not accept invalid
>      values for the attribute.
> 
>   drivers/hwmon/amc6821.c | 15 +++++++++------
>   1 file changed, 9 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/hwmon/amc6821.c b/drivers/hwmon/amc6821.c
> index 9b02b304c2f5..eb2d5592a41a 100644
> --- a/drivers/hwmon/amc6821.c
> +++ b/drivers/hwmon/amc6821.c
> @@ -355,13 +355,13 @@ static ssize_t pwm1_store(struct device *dev,
>   {
>   	struct amc6821_data *data = dev_get_drvdata(dev);
>   	struct i2c_client *client = data->client;
> -	long val;
> -	int ret = kstrtol(buf, 10, &val);
> +	u8 val;
> +	int ret = kstrtou8(buf, 10, &val);
>   	if (ret)
>   		return ret;
>   
>   	mutex_lock(&data->update_lock);
> -	data->pwm1 = clamp_val(val , 0, 255);
> +	data->pwm1 = val;
>   	i2c_smbus_write_byte_data(client, AMC6821_REG_DCY, data->pwm1);
>   	mutex_unlock(&data->update_lock);
>   	return count;
> @@ -558,13 +558,16 @@ static ssize_t pwm1_auto_point_pwm_store(struct device *dev,
>   	struct amc6821_data *data = dev_get_drvdata(dev);
>   	struct i2c_client *client = data->client;
>   	int dpwm;
> -	long val;
> -	int ret = kstrtol(buf, 10, &val);
> +	u8 val;
> +	int ret = kstrtou8(buf, 10, &val);
>   	if (ret)
>   		return ret;
>  
> +	if (val > 254)

Would have appreciated a comment as to why it's 254. My understanding is 
that the subsystem requires no overlap between multiple pwm_auto_points? 
0 being 0 and 2 being 255, we need 1 to be 255?

Actually, that doesn't explain why we allow 0 here, so maybe I'm just 
clueless :)

The change itself though:
Reviewed-by: Quentin Schulz <quentin.schulz@...rry.de>

Thanks!
Quentin