[PATCH v4 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
  IIO_CHAN_INFO_PRESET: Counter preset value

Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
---
 Documentation/ABI/testing/sysfs-bus-iio | 28 ++++++++++++++++++++++++++++
 drivers/iio/industrialio-core.c         |  3 +++
 include/linux/iio/iio.h                 |  1 +
 include/uapi/linux/iio/types.h          |  2 ++
 4 files changed, 34 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-bus-iio b/Documentation/ABI/testing/sysfs-bus-iio
index fee35c0..be66a41 100644
--- a/Documentation/ABI/testing/sysfs-bus-iio
+++ b/Documentation/ABI/testing/sysfs-bus-iio
@@ -1579,3 +1579,31 @@ 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, division 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_countY_scale
+KernelVersion:	4.9
+Contact:	linux-iio@vger.kernel.org
+Description:
+		If a scale value is available for channel Y, it is provided by
+		this attribute.
+
+What:		/sys/bus/iio/devices/iio:deviceX/in_countY_preset
+KernelVersion:	4.9
+Contact:	linux-iio@vger.kernel.org
+Description:
+		If the counter device supports preset registers, the preset
+		count for channel Y is provided by this attribute.
+
+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.
diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
index fc340ed..ed175a2 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[] = {
@@ -151,6 +153,7 @@ static const char * const iio_chan_info_postfix[] = {
 	[IIO_CHAN_INFO_DEBOUNCE_TIME] = "debounce_time",
 	[IIO_CHAN_INFO_CALIBEMISSIVITY] = "calibemissivity",
 	[IIO_CHAN_INFO_OVERSAMPLING_RATIO] = "oversampling_ratio",
+	[IIO_CHAN_INFO_PRESET] = "preset",
 };
 
 /**
diff --git a/include/linux/iio/iio.h b/include/linux/iio/iio.h
index b4a0679..7dc86d1 100644
--- a/include/linux/iio/iio.h
+++ b/include/linux/iio/iio.h
@@ -46,6 +46,7 @@ enum iio_chan_info_enum {
 	IIO_CHAN_INFO_DEBOUNCE_TIME,
 	IIO_CHAN_INFO_CALIBEMISSIVITY,
 	IIO_CHAN_INFO_OVERSAMPLING_RATIO,
+	IIO_CHAN_INFO_PRESET,
 };
 
 enum iio_shared_by {
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