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Sender: Guenter Roeck <groeck7@gmail.com>
Date:   Thu, 18 Aug 2022 13:13:59 -0700
From:   Guenter Roeck <linux@roeck-us.net>
To:     Eliav Farber <farbere@amazon.com>
Cc:     jdelvare@suse.com, robh+dt@kernel.org, mark.rutland@arm.com,
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Subject: Re: [PATCH v2 11/16] hwmon: (mr75203) add protection for negative
 voltage value
Message-ID: <20220818201359.GA3430651@roeck-us.net>
References: <20220817054321.6519-1-farbere@amazon.com>
 <20220817054321.6519-12-farbere@amazon.com>
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On Wed, Aug 17, 2022 at 05:43:16AM +0000, Eliav Farber wrote:
> This change makes sure the returned voltage vlaue is 0 or positive.
> 
> Signed-off-by: Eliav Farber <farbere@amazon.com>
> ---
>  drivers/hwmon/mr75203.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/hwmon/mr75203.c b/drivers/hwmon/mr75203.c
> index 24a00339cfd8..e3191f590167 100644
> --- a/drivers/hwmon/mr75203.c
> +++ b/drivers/hwmon/mr75203.c
> @@ -218,6 +218,13 @@ static int pvt_read_in(struct device *dev, u32 attr, int channel, long *val)
>  			return ret;
>  
>  		n &= SAMPLE_DATA_MSK;
> +
> +		/* Voltage can't be negative */

Who says, and what does that mean ? Under which conditions would
the value be negative, and why would that be a problem / bug ?
After all, negative voltages do exist.

Guenter

> +		if (PVT_N_CONST * n < PVT_R_CONST) {
> +			*val = 0;
> +			return 0;
> +		}
> +
>  		/* Convert the N bitstream count into voltage */
>  		*val = pvt->vd[channel].pre_scaler;
>  		*val *= (PVT_N_CONST * n - PVT_R_CONST);