The sensor support various thermocouple types (e.g. J, K, N, ...). The
driver allows to configure this parameter using a DT property.
This is useful when i.e. the thermocouple is physically tied to the sensor
and it is usually not removed, or when it is at least known in advace
which sensor will be connected to the circuit.
However, if the user can randomly connect any kind of thermocouples (i.e.
the device exposes a connector, and the user is free to connect its own
sensors), it would be more appropriate to provide a mechanism to
dynamically switch from one thermocouple type to another. This can be i.e.
handled in userspace by a GUI, a configuration file or a program that
detects the thermocouple type by reading a GPIO, or a eeprom on the probe,
or whatever.
This patch adds a IIO attribute that can be used to override, at run-time,
the DT-provided setting (which serves as default).
Signed-off-by: Andrea Merello <andrea.merello@xxxxxxxxx>
---
drivers/iio/temperature/max31856.c | 44 ++++++++++++++++++++++++++++++
1 file changed, 44 insertions(+)
diff --git a/drivers/iio/temperature/max31856.c b/drivers/iio/temperature/max31856.c
index 8b2e0102fa5c..588e791c79a3 100644
--- a/drivers/iio/temperature/max31856.c
+++ b/drivers/iio/temperature/max31856.c
@@ -6,6 +6,7 @@
* Copyright (C) 2018-2019 Rockwell Collins
*/
+#include <linux/ctype.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/err.h>
@@ -70,6 +71,10 @@ struct max31856_data {
int averaging;
};
+const char max31856_tc_types[] = {
+ 'B', 'E', 'J', 'K', 'N', 'R', 'S', 'T'
+};
+
static int max31856_read(struct max31856_data *data, u8 reg,
u8 val[], unsigned int read_size)
{
@@ -336,16 +341,55 @@ static ssize_t set_averaging(struct device *dev,
return len;
}
+static ssize_t show_tc_type(struct device *dev,
+ struct device_attribute *attr,
+ char *buf)
+{
+ struct iio_dev *indio_dev = dev_to_iio_dev(dev);
+ struct max31856_data *data = iio_priv(indio_dev);
+
+ return sprintf(buf, "%c\n", max31856_tc_types[data->thermocouple_type]);
+}
+
+static ssize_t set_tc_type(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf,
+ size_t len)
+{
+ struct iio_dev *indio_dev = dev_to_iio_dev(dev);
+ struct max31856_data *data = iio_priv(indio_dev);
+ char tmp;
+ int tc_type = -1;
+ int i;
+
+ if (sscanf(buf, "%c\n", &tmp) != 1)
+ return -EINVAL;
+
+ for (i = 0; i < ARRAY_SIZE(max31856_tc_types); i++) {
+ if (max31856_tc_types[i] == toupper(tmp)) {
+ tc_type = i;
+ break;
+ }
+ }
+ if (tc_type < 0)
+ return -EINVAL;
+ data->thermocouple_type = tc_type;
+ max31856_init(data);
+ return len;
+}
+
static IIO_DEVICE_ATTR(fault_ovuv, 0444, show_fault_ovuv, NULL, 0);
static IIO_DEVICE_ATTR(fault_oc, 0444, show_fault_oc, NULL, 0);
static IIO_DEVICE_ATTR(filter, 0644, show_filter, set_filter, 0);
static IIO_DEVICE_ATTR(averaging, 0644, show_averaging, set_averaging, 0);
+static IIO_DEVICE_ATTR(thermocouple_type, 0644, show_tc_type, set_tc_type, 0);
static struct attribute *max31856_attributes[] = {
&iio_dev_attr_fault_ovuv.dev_attr.attr,
&iio_dev_attr_fault_oc.dev_attr.attr,
&iio_dev_attr_filter.dev_attr.attr,
&iio_dev_attr_averaging.dev_attr.attr,
+ &iio_dev_attr_thermocouple_type.dev_attr.attr,
NULL,
};
--
2.17.1
