Re: [PATCH v2 2/5] hwmon: ina2xx: make shunt resistance configurable at run-time
From: Guenter Roeck
Date: Sun Nov 30 2014 - 14:45:57 EST
On 11/27/2014 01:59 AM, Bartosz Golaszewski wrote:
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@xxxxxxxxxxxx>
---
drivers/hwmon/ina2xx.c | 62 +++++++++++++++++++++++++++++++++++++++++++++-----
1 file changed, 56 insertions(+), 6 deletions(-)
diff --git a/drivers/hwmon/ina2xx.c b/drivers/hwmon/ina2xx.c
index 0a6b60f..341da67 100644
--- a/drivers/hwmon/ina2xx.c
+++ b/drivers/hwmon/ina2xx.c
@@ -51,6 +51,8 @@
#define INA226_ALERT_LIMIT 0x07
#define INA226_DIE_ID 0xFF
+/* shunt resistor sysfs attribute index */
+#define INA2XX_RSHUNT 0x8
/* register count */
#define INA219_REGISTERS 6
@@ -65,6 +67,9 @@
/* worst case is 68.10 ms (~14.6Hz, ina219) */
#define INA2XX_CONVERSION_RATE 15
+/* default shunt resistance */
+#define INA2XX_RSHUNT_DEFAULT 10000
+
enum ina2xx_ids { ina219, ina226 };
struct ina2xx_config {
@@ -87,6 +92,8 @@ struct ina2xx_data {
int kind;
u16 regs[INA2XX_MAX_REGISTERS];
+
+ long rshunt;
};
static const struct ina2xx_config ina2xx_config[] = {
@@ -110,6 +117,11 @@ static const struct ina2xx_config ina2xx_config[] = {
},
};
+static u16 ina2xx_calibration_val(const struct ina2xx_data *data)
+{
+ return data->config->calibration_factor / data->rshunt;
+}
+
static struct ina2xx_data *ina2xx_update_device(struct device *dev)
{
struct ina2xx_data *data = dev_get_drvdata(dev);
@@ -164,6 +176,9 @@ 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_RSHUNT:
+ val = data->rshunt;
+ break;
That doesn't make sense. You neither read the current shunt resistor value
with update_device, nor use the register value to calculate the programmed
shunt resistor value. Just define a separate show function which reports
rshunt as configured.
A better alternative would be to actually _read_ and report rshunt as
programmed into the chip. Otherwise you'll get the "old" value of rshunt
even if the chip was, as your use case suggests, pulled and re-inserted.
default:
/* programmer goofed */
WARN_ON_ONCE(1);
@@ -187,6 +202,35 @@ 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);
+ long val;
This should be unsigned long since you now use kstrtoul.
+ int status;
+
+ if (IS_ERR(data))
+ return PTR_ERR(data);
+
+ status = kstrtoul(buf, 10, &val);
+ if (status < 0)
+ return status;
This will accept a value of 0xffffffff which is then converted into -1
since data->rshunt is defined as long.
+
+ if (val == 0)
+ return -EINVAL;
+
+ mutex_lock(&data->update_lock);
+ data->rshunt = val;
+ status = i2c_smbus_write_word_swapped(data->client, INA2XX_CALIBRATION,
+ ina2xx_calibration_val(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);
@@ -203,12 +247,17 @@ 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 | S_IWGRP,
This will have to be S_IRUGO | S_IWUSR. We don't permit group writes.
+ ina2xx_show_value, ina2xx_set_shunt, INA2XX_RSHUNT);
+
/* 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);
@@ -221,7 +270,6 @@ static int ina2xx_probe(struct i2c_client *client,
struct device *dev = &client->dev;
struct ina2xx_data *data;
struct device *hwmon_dev;
- long shunt = 10000; /* default shunt value 10mOhms */
u32 val;
int ret;
@@ -234,13 +282,15 @@ static int ina2xx_probe(struct i2c_client *client,
if (dev_get_platdata(dev)) {
pdata = dev_get_platdata(dev);
- shunt = pdata->shunt_uohms;
+ data->rshunt = pdata->shunt_uohms;
} else if (!of_property_read_u32(dev->of_node,
"shunt-resistor", &val)) {
- shunt = val;
+ data->rshunt = val;
+ } else {
+ data->rshunt = INA2XX_RSHUNT_DEFAULT;
}
- if (shunt <= 0)
+ if (data->rshunt <= 0)
return -ENODEV;
/* set the device type */
@@ -260,7 +310,7 @@ static int ina2xx_probe(struct i2c_client *client,
* (equation 13 in datasheet).
*/
ret = i2c_smbus_write_word_swapped(client, INA2XX_CALIBRATION,
- data->config->calibration_factor / shunt);
+ ina2xx_calibration_val(data));
if (ret < 0) {
dev_err(dev,
"error writing to the calibration register: %d", ret);
@@ -276,7 +326,7 @@ static int ina2xx_probe(struct i2c_client *client,
return PTR_ERR(hwmon_dev);
dev_info(dev, "power monitor %s (Rshunt = %li uOhm)\n",
- id->name, shunt);
+ id->name, data->rshunt);
return 0;
}
--
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