iio: core: Add IIO_COVERAGE channel type

Add a new channel type for sensors that report fractional coverage as
a percentage. The sysfs attribute is in_coverageY_raw; after applying
in_coverageY_scale the value is in percent. The first user is the
ADT7604 leak detector, where the value represents the portion of the
sensing element that is wetted.

Signed-off-by: Liviu Stan <liviu.stan@analog.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

Author: leaveyoustun

Documentation/ABI/testing/sysfs-bus-iio

@@ -1980,6 +1980,23 @@ Description:
 		Raw (unscaled no offset etc.) resistance reading.
 		Units after application of scale and offset are ohms.
 
+What:		/sys/bus/iio/devices/iio:deviceX/in_coverageY_raw
+KernelVersion:	7.2
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Raw (unscaled no offset etc.) coverage reading. Used for sensors
+		that report fractional coverage as a percentage, such as leak
+		detectors where the value represents what portion of the sensing
+		element is wetted. Units after application of scale and offset are
+		percent.
+
+What:		/sys/bus/iio/devices/iio:deviceX/in_coverageY_scale
+KernelVersion:	7.2
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Scale to be applied to in_coverageY_raw to obtain coverage
+		in percent.
+
 What:		/sys/bus/iio/devices/iio:deviceX/heater_enable
 KernelVersion:	4.1.0
 Contact:	linux-iio@vger.kernel.org

drivers/iio/industrialio-core.c

@@ -98,6 +98,7 @@ static const char * const iio_chan_type_name_spec[] = {
 	[IIO_CHROMATICITY] = "chromaticity",
 	[IIO_ATTENTION] = "attention",
 	[IIO_ALTCURRENT] = "altcurrent",
+	[IIO_COVERAGE] = "coverage",
 };
 
 static const char * const iio_modifier_names[] = {

include/uapi/linux/iio/types.h

@@ -53,6 +53,7 @@ enum iio_chan_type {
 	IIO_CHROMATICITY,
 	IIO_ATTENTION,
 	IIO_ALTCURRENT,
+	IIO_COVERAGE,
 };
 
 enum iio_modifier {

tools/iio/iio_event_monitor.c

@@ -65,6 +65,7 @@ static const char * const iio_chan_type_name_spec[] = {
 	[IIO_CHROMATICITY] = "chromaticity",
 	[IIO_ATTENTION] = "attention",
 	[IIO_ALTCURRENT] = "altcurrent",
+	[IIO_COVERAGE] = "coverage",
 };
 
 static const char * const iio_ev_type_text[] = {
@@ -194,6 +195,7 @@ static bool event_is_known(struct iio_event_data *event)
 	case IIO_CHROMATICITY:
 	case IIO_ATTENTION:
 	case IIO_ALTCURRENT:
+	case IIO_COVERAGE:
 		break;
 	default:
 		return false;