iio: introduce mag_referenced

Some accelerometers that support activity and inactivity
events also support a referenced mode, in which the
gravitational acceleration is taken as a point of
reference before comparing the acceleration to the
specified activity and inactivity magnitude.

For example, in the case of the ADXL367, for activity
detection, the formula is:

abs(acceleration - reference) > magnitude

Add a new event type that makes this behavior clear.

Signed-off-by: Cosmin Tanislav <cosmin.tanislav@analog.com>
Link: https://lore.kernel.org/r/20220214073810.781016-2-cosmin.tanislav@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/industrialio-event.c

@@ -230,6 +230,7 @@ static const char * const iio_ev_type_text[] = {
 	[IIO_EV_TYPE_THRESH_ADAPTIVE] = "thresh_adaptive",
 	[IIO_EV_TYPE_MAG_ADAPTIVE] = "mag_adaptive",
 	[IIO_EV_TYPE_CHANGE] = "change",
+	[IIO_EV_TYPE_MAG_REFERENCED] = "mag_referenced",
 };
 
 static const char * const iio_ev_dir_text[] = {

include/uapi/linux/iio/types.h

@@ -104,6 +104,7 @@ enum iio_event_type {
 	IIO_EV_TYPE_THRESH_ADAPTIVE,
 	IIO_EV_TYPE_MAG_ADAPTIVE,
 	IIO_EV_TYPE_CHANGE,
+	IIO_EV_TYPE_MAG_REFERENCED,
 };
 
 enum iio_event_direction {

tools/iio/iio_event_monitor.c

@@ -68,6 +68,7 @@ static const char * const iio_ev_type_text[] = {
 	[IIO_EV_TYPE_THRESH_ADAPTIVE] = "thresh_adaptive",
 	[IIO_EV_TYPE_MAG_ADAPTIVE] = "mag_adaptive",
 	[IIO_EV_TYPE_CHANGE] = "change",
+	[IIO_EV_TYPE_MAG_REFERENCED] = "mag_referenced",
 };
 
 static const char * const iio_ev_dir_text[] = {