iio: Add IIO_DELTA_ANGL channel type

The delta angle is defined as a piece-wise integration of angular
velocity data. The delta angle represents the amount of
angular displacement between two consecutive measurements and it
is measured in radians.

In order to track the total angular displacement during a desired
period of time, simply sum-up the delta angle samples acquired
during that time.

IIO currently does not offer a suitable channel type for this
type of measurements hence this patch adds it.
Signed-off-by: Ramona Bolboaca <ramona.bolboaca@analog.com>
Reviewed-by: Nuno Sa <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20230808075059.645525-2-ramona.bolboaca@analog.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Documentation/ABI/testing/sysfs-bus-iio

@@ -279,6 +279,20 @@ Description:
 		but should match other such assignments on device).
 		Units after application of scale and offset are m/s^2.
 
+What:		/sys/bus/iio/devices/iio:deviceX/in_deltaangl_x_raw
+What:		/sys/bus/iio/devices/iio:deviceX/in_deltaangl_y_raw
+What:		/sys/bus/iio/devices/iio:deviceX/in_deltaangl_z_raw
+KernelVersion:	6.5
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Angular displacement between two consecutive samples on x, y or
+		z (may be arbitrarily assigned but should match other such
+		assignments on device).
+		In order to compute the total angular displacement during a
+		desired period of time, the application should sum-up the delta
+		angle samples acquired during that time.
+		Units after application of scale and offset are radians.
+
 What:		/sys/bus/iio/devices/iio:deviceX/in_angl_raw
 What:		/sys/bus/iio/devices/iio:deviceX/in_anglY_raw
 KernelVersion:	4.17
@@ -461,6 +475,7 @@ What:		/sys/bus/iio/devices/iio:deviceX/in_humidityrelative_scale
 What:		/sys/bus/iio/devices/iio:deviceX/in_velocity_sqrt(x^2+y^2+z^2)_scale
 What:		/sys/bus/iio/devices/iio:deviceX/in_illuminance_scale
 What:		/sys/bus/iio/devices/iio:deviceX/in_countY_scale
+What:		/sys/bus/iio/devices/iio:deviceX/in_deltaangl_scale
 What:		/sys/bus/iio/devices/iio:deviceX/in_angl_scale
 What:		/sys/bus/iio/devices/iio:deviceX/in_intensity_x_scale
 What:		/sys/bus/iio/devices/iio:deviceX/in_intensity_y_scale
@@ -1332,6 +1347,9 @@ Description:
 What:		/sys/.../iio:deviceX/bufferY/in_accel_x_en
 What:		/sys/.../iio:deviceX/bufferY/in_accel_y_en
 What:		/sys/.../iio:deviceX/bufferY/in_accel_z_en
+What:		/sys/.../iio:deviceX/bufferY/in_deltaangl_x_en
+What:		/sys/.../iio:deviceX/bufferY/in_deltaangl_y_en
+What:		/sys/.../iio:deviceX/bufferY/in_deltaangl_z_en
 What:		/sys/.../iio:deviceX/bufferY/in_anglvel_x_en
 What:		/sys/.../iio:deviceX/bufferY/in_anglvel_y_en
 What:		/sys/.../iio:deviceX/bufferY/in_anglvel_z_en
@@ -1362,6 +1380,7 @@ Description:
 		Scan element control for triggered data capture.
 
 What:		/sys/.../iio:deviceX/bufferY/in_accel_type
+What:		/sys/.../iio:deviceX/bufferY/in_deltaangl_type
 What:		/sys/.../iio:deviceX/bufferY/in_anglvel_type
 What:		/sys/.../iio:deviceX/bufferY/in_magn_type
 What:		/sys/.../iio:deviceX/bufferY/in_incli_type
@@ -1416,6 +1435,9 @@ What:		/sys/.../iio:deviceX/bufferY/in_voltage_q_index
 What:		/sys/.../iio:deviceX/bufferY/in_accel_x_index
 What:		/sys/.../iio:deviceX/bufferY/in_accel_y_index
 What:		/sys/.../iio:deviceX/bufferY/in_accel_z_index
+What:		/sys/.../iio:deviceX/bufferY/in_deltaangl_x_index
+What:		/sys/.../iio:deviceX/bufferY/in_deltaangl_y_index
+What:		/sys/.../iio:deviceX/bufferY/in_deltaangl_z_index
 What:		/sys/.../iio:deviceX/bufferY/in_anglvel_x_index
 What:		/sys/.../iio:deviceX/bufferY/in_anglvel_y_index
 What:		/sys/.../iio:deviceX/bufferY/in_anglvel_z_index

drivers/iio/industrialio-core.c

@@ -90,6 +90,7 @@ static const char * const iio_chan_type_name_spec[] = {
 	[IIO_POSITIONRELATIVE]  = "positionrelative",
 	[IIO_PHASE] = "phase",
 	[IIO_MASSCONCENTRATION] = "massconcentration",
+	[IIO_DELTA_ANGL] = "deltaangl",
 };
 
 static const char * const iio_modifier_names[] = {

include/uapi/linux/iio/types.h

@@ -47,6 +47,7 @@ enum iio_chan_type {
 	IIO_POSITIONRELATIVE,
 	IIO_PHASE,
 	IIO_MASSCONCENTRATION,
+	IIO_DELTA_ANGL,
 };
 
 enum iio_modifier {

tools/iio/iio_event_monitor.c

@@ -59,6 +59,7 @@ static const char * const iio_chan_type_name_spec[] = {
 	[IIO_POSITIONRELATIVE] = "positionrelative",
 	[IIO_PHASE] = "phase",
 	[IIO_MASSCONCENTRATION] = "massconcentration",
+	[IIO_DELTA_ANGL] = "deltaangl",
 };
 
 static const char * const iio_ev_type_text[] = {
@@ -173,6 +174,7 @@ static bool event_is_known(struct iio_event_data *event)
 	case IIO_POSITIONRELATIVE:
 	case IIO_PHASE:
 	case IIO_MASSCONCENTRATION:
+	case IIO_DELTA_ANGL:
 		break;
 	default:
 		return false;