linux-kernel - Re: [PATCH] hwmon: (ina2xx) Fix current value calculation

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Date:   Wed, 14 Nov 2018 09:12:22 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     Nicolin Chen <nicoleotsuka@...il.com>
Cc:     jdelvare@...e.com, linux-hwmon@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] hwmon: (ina2xx) Fix current value calculation

On Tue, Nov 13, 2018 at 07:48:54PM -0800, Nicolin Chen wrote:
> The current register (04h) has a sign bit at MSB. The comments
> for this calculation also mention that it's a signed register.
> 
> However, the regval is unsigned type so result of calculation
> turns out to be an incorrect value when current is negative.
> 
> This patch simply fixes this by adding a casting to s16.
> 
> Signed-off-by: Nicolin Chen <nicoleotsuka@...il.com>

Applied.

Thanks,
Guenter

> ---
>  drivers/hwmon/ina2xx.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/hwmon/ina2xx.c b/drivers/hwmon/ina2xx.c
> index c2252cf452f5..07ee19573b3f 100644
> --- a/drivers/hwmon/ina2xx.c
> +++ b/drivers/hwmon/ina2xx.c
> @@ -274,7 +274,7 @@ static int ina2xx_get_value(struct ina2xx_data *data, u8 reg,
>  		break;
>  	case INA2XX_CURRENT:
>  		/* signed register, result in mA */
> -		val = regval * data->current_lsb_uA;
> +		val = (s16)regval * data->current_lsb_uA;
>  		val = DIV_ROUND_CLOSEST(val, 1000);
>  		break;
>  	case INA2XX_CALIBRATION:
> -- 
> 2.17.1
>