[PATCH v5 1/2] iio: Implement counter channel type and info constants

[William Breathitt Gray <vilhelm.gray@gmail.com>]

Quadrature encoders, such as rotary encoders and linear encoders, are
devices which are capable of encoding the relative position and
direction of motion of a shaft. This patch introduces several IIO
constants for supporting quadrature encoder counter devices.

  IIO_COUNT: Current count (main data provided by the counter device)
  IIO_INDEX: Counter device index value

Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
---
 Documentation/ABI/testing/sysfs-bus-iio | 18 ++++++++++++++++++
 drivers/iio/industrialio-core.c         |  2 ++
 include/uapi/linux/iio/types.h          |  2 ++
 3 files changed, 22 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-bus-iio b/Documentation/ABI/testing/sysfs-bus-iio
index fee35c0..b8f220f 100644
--- a/Documentation/ABI/testing/sysfs-bus-iio
+++ b/Documentation/ABI/testing/sysfs-bus-iio
@@ -329,6 +329,7 @@ What:		/sys/bus/iio/devices/iio:deviceX/in_pressure_scale
 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
 KernelVersion:	2.6.35
 Contact:	linux-iio@vger.kernel.org
 Description:
@@ -1579,3 +1580,20 @@ Contact:	linux-iio@vger.kernel.org
 Description:
 		Raw (unscaled no offset etc.) electric conductivity reading that
 		can be processed to siemens per meter.
+
+What:		/sys/bus/iio/devices/iio:deviceX/in_countY_raw
+KernelVersion:	4.9
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Raw counter device counts from channel Y. For quadrature
+		counters, multiplication by an available [Y]_scale results in
+		the counts of a single quadrature signal phase from channel Y.
+
+What:		/sys/bus/iio/devices/iio:deviceX/in_indexY_raw
+KernelVersion:	4.9
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Raw counter device index value from channel Y. This attribute
+		provides an absolute positional reference (e.g. a pulse once per
+		revolution) which may be used to home positional systems as
+		required.
diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
index fc340ed..649725b 100644
--- a/drivers/iio/industrialio-core.c
+++ b/drivers/iio/industrialio-core.c
@@ -81,6 +81,8 @@ static const char * const iio_chan_type_name_spec[] = {
 	[IIO_PH] = "ph",
 	[IIO_UVINDEX] = "uvindex",
 	[IIO_ELECTRICALCONDUCTIVITY] = "electricalconductivity",
+	[IIO_COUNT] = "count",
+	[IIO_INDEX] = "index",
 };
 
 static const char * const iio_modifier_names[] = {
diff --git a/include/uapi/linux/iio/types.h b/include/uapi/linux/iio/types.h
index 22e5e58..e54d14a 100644
--- a/include/uapi/linux/iio/types.h
+++ b/include/uapi/linux/iio/types.h
@@ -40,6 +40,8 @@ enum iio_chan_type {
 	IIO_PH,
 	IIO_UVINDEX,
 	IIO_ELECTRICALCONDUCTIVITY,
+	IIO_COUNT,
+	IIO_INDEX,
 };
 
 enum iio_modifier {
-- 
2.7.3