* [PATCH] hwmon: (ina2xx) Fix current value calculation
@ 2018-11-14 3:48 Nicolin Chen
0 siblings, 0 replies; 2+ messages in thread
From: Nicolin Chen @ 2018-11-14 3:48 UTC (permalink / raw)
To: jdelvare, linux; +Cc: linux-hwmon, linux-kernel
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@gmail.com>
---
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
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] hwmon: (ina2xx) Fix current value calculation
@ 2018-11-14 17:12 Guenter Roeck
0 siblings, 0 replies; 2+ messages in thread
From: Guenter Roeck @ 2018-11-14 17:12 UTC (permalink / raw)
To: Nicolin Chen; +Cc: jdelvare, linux-hwmon, linux-kernel
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@gmail.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
>
^ permalink raw reply [flat|nested] 2+ messages in thread
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2018-11-14 3:48 [PATCH] hwmon: (ina2xx) Fix current value calculation Nicolin Chen
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