iio: Add IIO_DELTA_VELOCITY channel type

The delta velocity is defined as a piece-wise integration of
acceleration data. The delta velocity represents the linear velocity
change between two consecutive measurements and it
is measured in m / s (meters per second).

In order to track the total linear velocity change during a desired
period of time, simply sum-up the delta velocity 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/20230808075059.645525-3-ramona.bolboaca@analog.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Documentation/ABI/testing/sysfs-bus-iio

@@ -293,6 +293,21 @@ Description:
 		angle samples acquired during that time.
 		Units after application of scale and offset are radians.
 
+What:		/sys/bus/iio/devices/iio:deviceX/in_deltavelocity_x_raw
+What:		/sys/bus/iio/devices/iio:deviceX/in_deltavelocity_y_raw
+What:		/sys/bus/iio/devices/iio:deviceX/in_deltavelocity_z_raw
+KernelVersion:	6.5
+Contact:	linux-iio@vger.kernel.org
+Description:
+		The linear velocity change 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 linear velocity change during a
+		desired period of time, the application should sum-up the delta
+		velocity samples acquired during that time.
+		Units after application of scale and offset are meters per
+		second.
+
 What:		/sys/bus/iio/devices/iio:deviceX/in_angl_raw
 What:		/sys/bus/iio/devices/iio:deviceX/in_anglY_raw
 KernelVersion:	4.17
@@ -476,6 +491,7 @@ 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_deltavelocity_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
@@ -1350,6 +1366,9 @@ 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_deltavelocity_x_en
+What:		/sys/.../iio:deviceX/bufferY/in_deltavelocity_y_en
+What:		/sys/.../iio:deviceX/bufferY/in_deltavelocity_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
@@ -1381,6 +1400,7 @@ Description:
 
 What:		/sys/.../iio:deviceX/bufferY/in_accel_type
 What:		/sys/.../iio:deviceX/bufferY/in_deltaangl_type
+What:		/sys/.../iio:deviceX/bufferY/in_deltavelocity_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
@@ -1438,6 +1458,9 @@ 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_deltavelocity_x_index
+What:		/sys/.../iio:deviceX/bufferY/in_deltavelocity_y_index
+What:		/sys/.../iio:deviceX/bufferY/in_deltavelocity_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

@@ -91,6 +91,7 @@ static const char * const iio_chan_type_name_spec[] = {
 	[IIO_PHASE] = "phase",
 	[IIO_MASSCONCENTRATION] = "massconcentration",
 	[IIO_DELTA_ANGL] = "deltaangl",
+	[IIO_DELTA_VELOCITY] = "deltavelocity",
 };
 
 static const char * const iio_modifier_names[] = {

include/uapi/linux/iio/types.h

@@ -48,6 +48,7 @@ enum iio_chan_type {
 	IIO_PHASE,
 	IIO_MASSCONCENTRATION,
 	IIO_DELTA_ANGL,
+	IIO_DELTA_VELOCITY,
 };
 
 enum iio_modifier {

tools/iio/iio_event_monitor.c

@@ -60,6 +60,7 @@ static const char * const iio_chan_type_name_spec[] = {
 	[IIO_PHASE] = "phase",
 	[IIO_MASSCONCENTRATION] = "massconcentration",
 	[IIO_DELTA_ANGL] = "deltaangl",
+	[IIO_DELTA_VELOCITY] = "deltavelocity",
 };
 
 static const char * const iio_ev_type_text[] = {
@@ -175,6 +176,7 @@ static bool event_is_known(struct iio_event_data *event)
 	case IIO_PHASE:
 	case IIO_MASSCONCENTRATION:
 	case IIO_DELTA_ANGL:
+	case IIO_DELTA_VELOCITY:
 		break;
 	default:
 		return false;