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: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

diff --git a/Documentation/hwmon/ina2xx b/Documentation/hwmon/ina2xx
index 4223c2d..320dd69 100644 (file)
--- a/Documentation/hwmon/ina2xx
+++ b/Documentation/hwmon/ina2xx
@@ -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.

diff --git a/drivers/hwmon/ina2xx.c b/drivers/hwmon/ina2xx.c
index 3234e57..49537ea 100644 (file)
--- a/drivers/hwmon/ina2xx.c
+++ b/drivers/hwmon/ina2xx.c
@@ -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);