iio: Add channel for Phase

Add new channel type support for phase.

This channel may be used by Time-of-flight sensors to express the
phase difference between emitted and received signals. Those sensor
will then use the phase shift of return signals to approximate the
distance to objects.

Signed-off-by: Mathieu Othacehe <m.othacehe@gmail.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Author: mothacehe

Documentation/ABI/testing/sysfs-bus-iio

@@ -1675,3 +1675,10 @@ KernelVersion:	4.12
 Contact:	linux-iio@vger.kernel.org
 Description:
 		Raw counter device counters direction for channel Y.
+
+What:		/sys/bus/iio/devices/iio:deviceX/in_phaseY_raw
+KernelVersion:	4.18
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Raw (unscaled) phase difference reading from channel Y
+		that can be processed to radians.

drivers/iio/industrialio-core.c

@@ -86,6 +86,7 @@ static const char * const iio_chan_type_name_spec[] = {
 	[IIO_INDEX] = "index",
 	[IIO_GRAVITY]  = "gravity",
 	[IIO_POSITIONRELATIVE]  = "positionrelative",
+	[IIO_PHASE] = "phase",
 };
 
 static const char * const iio_modifier_names[] = {

include/uapi/linux/iio/types.h

@@ -45,6 +45,7 @@ enum iio_chan_type {
 	IIO_INDEX,
 	IIO_GRAVITY,
 	IIO_POSITIONRELATIVE,
+	IIO_PHASE,
 };
 
 enum iio_modifier {

tools/iio/iio_event_monitor.c

@@ -59,6 +59,7 @@ static const char * const iio_chan_type_name_spec[] = {
 	[IIO_UVINDEX] = "uvindex",
 	[IIO_GRAVITY] = "gravity",
 	[IIO_POSITIONRELATIVE] = "positionrelative",
+	[IIO_PHASE] = "phase",
 };
 
 static const char * const iio_ev_type_text[] = {
@@ -153,6 +154,7 @@ static bool event_is_known(struct iio_event_data *event)
 	case IIO_UVINDEX:
 	case IIO_GRAVITY:
 	case IIO_POSITIONRELATIVE:
+	case IIO_PHASE:
 		break;
 	default:
 		return false;