iio: core: Introduce IIO_CHAN_INFO_DEBOUNCE_COUNT and _TIME

The pedometer needs to filter out false steps that might be generated by
tapping the foot, sitting, etc. To do that it computes the number of
steps that occur in a given time and decides the user is moving only
if this value is over a threshold. E.g.: the user starts moving only
if he takes 4 steps in 3 seconds. This filter is applied only when
the user starts moving.

A device that has such pedometer functionality is Freescale's MMA9553L:
http://www.freescale.com/files/sensors/doc/ref_manual/MMA9553LSWRM.pdf.

To export this feature, this patch introduces IIO_CHAN_INFO_DEBOUNCE_COUNT
and IIO_CHAN_INFO_DEBOUNCE_TIME. For the pedometer, in_steps_debounce_count
will specify the number of steps that need to occur in
in_steps_debounce_time seconds so that the pedometer decides the user is
moving.

Signed-off-by: Irina Tirdea <irina.tirdea@intel.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

Documentation/ABI/testing/sysfs-bus-iio

@@ -1193,3 +1193,18 @@ Description:
 		This attribute is used to read the current speed value of the
 		user (which is the norm or magnitude of the velocity vector).
 		Units after application of scale are m/s.
+
+What:		/sys/.../iio:deviceX/in_steps_debounce_count
+KernelVersion:	3.20
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Specifies the number of steps that must occur within
+		in_steps_filter_debounce_time for the pedometer to decide the
+		consumer is making steps.
+
+What:		/sys/.../iio:deviceX/in_steps_debounce_time
+KernelVersion:	3.20
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Specifies number of seconds in which we compute the steps
+		that occur in order to decide if the consumer is making steps.

drivers/iio/industrialio-core.c

@@ -126,6 +126,8 @@ static const char * const iio_chan_info_postfix[] = {
 	[IIO_CHAN_INFO_ENABLE] = "en",
 	[IIO_CHAN_INFO_CALIBHEIGHT] = "calibheight",
 	[IIO_CHAN_INFO_CALIBWEIGHT] = "calibweight",
+	[IIO_CHAN_INFO_DEBOUNCE_COUNT] = "debounce_count",
+	[IIO_CHAN_INFO_DEBOUNCE_TIME] = "debounce_time",
 };
 
 /**

include/linux/iio/iio.h

@@ -41,6 +41,8 @@ enum iio_chan_info_enum {
 	IIO_CHAN_INFO_ENABLE,
 	IIO_CHAN_INFO_CALIBHEIGHT,
 	IIO_CHAN_INFO_CALIBWEIGHT,
+	IIO_CHAN_INFO_DEBOUNCE_COUNT,
+	IIO_CHAN_INFO_DEBOUNCE_TIME,
 };
 
 enum iio_shared_by {