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Commit 8a5fc795 authored by Bartosz Golaszewski's avatar Bartosz Golaszewski Committed by Guenter Roeck
Browse files

hwmon: (ina2xx) make shunt resistance configurable at run-time 



The shunt resistance can only be set via platform_data or device tree. This
isn't suitable for devices in which the shunt resistance can change/isn't
known at boot-time.

Add a sysfs attribute that allows to read and set the shunt resistance.

Signed-off-by: default avatarBartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: default avatarGuenter Roeck <linux@roeck-us.net>
parent e7947040

Documentation/hwmon/ina2xx

+3 −2
Original line number Diff line number Diff line
@@ -44,6 +44,7 @@ The INA226 monitors both a shunt voltage drop and bus supply voltage. 
The INA230 is a high or low side current shunt and power monitor with an I2C

interface. The INA230 monitors both a shunt voltage drop and bus supply voltage.



The shunt value in micro-ohms can be set via platform data or device tree.

Please refer to the Documentation/devicetree/bindings/i2c/ina2xx.txt for bindings

The shunt value in micro-ohms can be set via platform data or device tree at

compile-time or via the shunt_resistor attribute in sysfs at run-time. Please

refer to the Documentation/devicetree/bindings/i2c/ina2xx.txt for bindings

if the device tree is used.

drivers/hwmon/ina2xx.c

+46 −2
Original line number Diff line number Diff line
@@ -115,6 +115,12 @@ static const struct ina2xx_config ina2xx_config[] = { 
	},

};



static int ina2xx_calibrate(struct ina2xx_data *data)

{

	return i2c_smbus_write_word_swapped(data->client, INA2XX_CALIBRATION,

			data->config->calibration_factor / data->rshunt);

}



/*

 * Initialize the configuration and calibration registers.

 */
@@ -133,8 +139,7 @@ static int ina2xx_init(struct ina2xx_data *data) 
	 * Set current LSB to 1mA, shunt is in uOhms

	 * (equation 13 in datasheet).

	 */

	return i2c_smbus_write_word_swapped(client, INA2XX_CALIBRATION,

			data->config->calibration_factor / data->rshunt);

	return ina2xx_calibrate(data);

}



static int ina2xx_do_update(struct device *dev)
@@ -231,6 +236,9 @@ static int ina2xx_get_value(struct ina2xx_data *data, u8 reg) 
		/* signed register, LSB=1mA (selected), in mA */

		val = (s16)data->regs[reg];

		break;

	case INA2XX_CALIBRATION:

		val = data->config->calibration_factor / data->regs[reg];

		break;

	default:

		/* programmer goofed */

		WARN_ON_ONCE(1);
@@ -254,6 +262,36 @@ static ssize_t ina2xx_show_value(struct device *dev, 
			ina2xx_get_value(data, attr->index));

}



static ssize_t ina2xx_set_shunt(struct device *dev,

				struct device_attribute *da,

				const char *buf, size_t count)

{

	struct ina2xx_data *data = ina2xx_update_device(dev);

	unsigned long val;

	int status;



	if (IS_ERR(data))

		return PTR_ERR(data);



	status = kstrtoul(buf, 10, &val);

	if (status < 0)

		return status;



	if (val == 0 ||

	    /* Values greater than the calibration factor make no sense. */

	    val > data->config->calibration_factor)

		return -EINVAL;



	mutex_lock(&data->update_lock);

	data->rshunt = val;

	status = ina2xx_calibrate(data);

	mutex_unlock(&data->update_lock);

	if (status < 0)

		return status;



	return count;

}



/* shunt voltage */

static SENSOR_DEVICE_ATTR(in0_input, S_IRUGO, ina2xx_show_value, NULL,

			  INA2XX_SHUNT_VOLTAGE);
@@ -270,12 +308,18 @@ static SENSOR_DEVICE_ATTR(curr1_input, S_IRUGO, ina2xx_show_value, NULL, 
static SENSOR_DEVICE_ATTR(power1_input, S_IRUGO, ina2xx_show_value, NULL,

			  INA2XX_POWER);



/* shunt resistance */

static SENSOR_DEVICE_ATTR(shunt_resistor, S_IRUGO | S_IWUSR,

			  ina2xx_show_value, ina2xx_set_shunt,

			  INA2XX_CALIBRATION);



/* pointers to created device attributes */

static struct attribute *ina2xx_attrs[] = {

	&sensor_dev_attr_in0_input.dev_attr.attr,

	&sensor_dev_attr_in1_input.dev_attr.attr,

	&sensor_dev_attr_curr1_input.dev_attr.attr,

	&sensor_dev_attr_power1_input.dev_attr.attr,

	&sensor_dev_attr_shunt_resistor.dev_attr.attr,

	NULL,

};

ATTRIBUTE_GROUPS(ina2xx);