Re: [PATCH] hwmon: (gpd-fan) Reject EC PWM value 0 as invalid

[Cryolitia PukNgae]

On 6/9/26 07:41, Pei Xiao wrote:
> The EC firmware is expected to return values in [1, pwm_max]. A read of 0
> is illegal and would cause underflow in the conversion formula. Explicitly
> check for 0 and return -EIO.
>
> Signed-off-by: Pei Xiao <xiaopei01@xxxxxxxxxx>
> ---
>   drivers/hwmon/gpd-fan.c | 6 +++++-
>   1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/hwmon/gpd-fan.c b/drivers/hwmon/gpd-fan.c
> index d1993cd645cb..decb61936b95 100644
> --- a/drivers/hwmon/gpd-fan.c
> +++ b/drivers/hwmon/gpd-fan.c
> @@ -341,7 +341,11 @@ static int gpd_wm2_read_pwm(struct gpd_fan_data *data)
>   
>   	gpd_ecram_read(drvdata, drvdata->pwm_write, &var);
>   
> -	// Match gpd_generic_write_pwm(u8) below
> +	/* EC PWM register valid range is 1 ~ pwm_max; 0 is an invalid state */
> +	if (unlikely(!var))
> +		return -EIO;
> +
> +	/* Match gpd_generic_write_pwm() below */
>   	return DIV_ROUND_CLOSEST((var - 1) * 255, (drvdata->pwm_max - 1));
>   }
>   

Have you ever tested the behavior on a real device? When it returns 0, 
what state is the device in?


thanks,

Cryolitia PukNgae