The INA238 sensor reports shunt voltage with microvolt precision.
However, the hwmon driver currently exposes this value only in
millivolts via `in0_input`, which results in a loss of precision for
readings within the range of ±1 mV.
This patch introduces an `in0_scale` attribute to provide the scaling
factor applied to the shunt voltage reading. By exposing this attribute,
users can accurately interpret the in0_input values in microvolts,
preserving the sensor's full precision.
Signed-off-by: Potin Lai <potin.lai.pt@xxxxxxxxx>
---
drivers/hwmon/ina238.c | 45 ++++++++++++++++++++++++++++++++++++++++++---
1 file changed, 42 insertions(+), 3 deletions(-)
diff --git a/drivers/hwmon/ina238.c b/drivers/hwmon/ina238.c
index 2d9f12f68d50..58737a0703dc 100644
--- a/drivers/hwmon/ina238.c
+++ b/drivers/hwmon/ina238.c
@@ -8,6 +8,7 @@
#include <linux/err.h>
#include <linux/hwmon.h>
+#include <linux/hwmon-sysfs.h>
#include <linux/i2c.h>
#include <linux/init.h>
#include <linux/kernel.h>
@@ -108,8 +109,42 @@ struct ina238_data {
struct regmap *regmap;
u32 rshunt;
int gain;
+ long shunt_volt_scale;
};
+static ssize_t shunt_volt_scale_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct ina238_data *data = dev_get_drvdata(dev);
+
+ return sprintf(buf, "%d\n", data->shunt_volt_scale);
+}
+
+static ssize_t shunt_volt_scale_store(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ struct ina238_data *data = dev_get_drvdata(dev);
+ long val;
+ int err;
+
+ err = kstrtol(buf, 10, &val);
+ if (err)
+ return err;
+
+ data->shunt_volt_scale = val;
+ return count;
+}
+
+static SENSOR_DEVICE_ATTR_RW(in0_scale, shunt_volt_scale, 0);
+
+static struct attribute *ina238_attrs[] = {
+ &sensor_dev_attr_in0_scale.dev_attr.attr,
+ NULL,
+};
+
+ATTRIBUTE_GROUPS(ina238);
+
static int ina238_read_reg24(const struct i2c_client *client, u8 reg, u32 *val)
{
u8 data[3];
@@ -197,8 +232,9 @@ static int ina238_read_in(struct device *dev, u32 attr, int channel,
regval = (s16)regval;
if (channel == 0)
/* gain of 1 -> LSB / 4 */
- *val = (regval * INA238_SHUNT_VOLTAGE_LSB) /
- (1000 * (4 - data->gain + 1));
+ *val = (regval * INA238_SHUNT_VOLTAGE_LSB *
+ data->shunt_volt_scale) /
+ (1000 * (4 - data->gain + 1));
else
*val = (regval * INA238_BUS_VOLTAGE_LSB) / 1000;
break;
@@ -603,9 +639,12 @@ static int ina238_probe(struct i2c_client *client)
return -ENODEV;
}
+ /* Setup default shunt voltage scale */
+ data->shunt_volt_scale = 1;
+
hwmon_dev = devm_hwmon_device_register_with_info(dev, client->name, data,
&ina238_chip_info,
- NULL);
+ ina238_groups);
if (IS_ERR(hwmon_dev))
return PTR_ERR(hwmon_dev);
---
base-commit: fc033cf25e612e840e545f8d5ad2edd6ba613ed5
change-id: 20250121-potin-ina238-shunt-voltage-scaling-8a3f9dc3d2b8
Best regards,
--
Potin Lai <potin.lai.pt@xxxxxxxxx>
