staging:iio: filter description - low pass 3db frequency.

Introduce the first data filtering related parameter.
For now we are ignoring the filter type and merely specifying its
approximate (I read them off tiny graphs) 3db point.
Signed-off-by: Jonathan Cameron <jic23@cam.ac.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/iio/iio.h

@@ -35,6 +35,7 @@ enum iio_chan_info_enum {
 	IIO_CHAN_INFO_PEAK_SCALE,
 	IIO_CHAN_INFO_QUADRATURE_CORRECTION_RAW,
 	IIO_CHAN_INFO_AVERAGE_RAW,
+	IIO_CHAN_INFO_LOW_PASS_FILTER_3DB_FREQUENCY,
 };
 
 #define IIO_CHAN_INFO_SHARED_BIT(type) BIT(type*2)
@@ -74,6 +75,12 @@ enum iio_chan_info_enum {
 	IIO_CHAN_INFO_SEPARATE_BIT(IIO_CHAN_INFO_AVERAGE_RAW)
 #define IIO_CHAN_INFO_AVERAGE_RAW_SHARED_BIT			\
 	IIO_CHAN_INFO_SHARED_BIT(IIO_CHAN_INFO_AVERAGE_RAW)
+#define IIO_CHAN_INFO_LOW_PASS_FILTER_3DB_FREQUENCY_SHARED_BIT \
+	IIO_CHAN_INFO_SHARED_BIT(			       \
+		IIO_CHAN_INFO_LOW_PASS_FILTER_3DB_FREQUENCY)
+#define IIO_CHAN_INFO_LOW_PASS_FILTER_3DB_FREQUENCY_SEPARATE_BIT \
+	IIO_CHAN_INFO_SEPARATE_BIT(			       \
+		IIO_CHAN_INFO_LOW_PASS_FILTER_3DB_FREQUENCY)
 
 enum iio_endian {
 	IIO_CPU,

drivers/staging/iio/industrialio-core.c

@@ -85,6 +85,8 @@ static const char * const iio_chan_info_postfix[] = {
 	[IIO_CHAN_INFO_PEAK_SCALE] = "peak_scale",
 	[IIO_CHAN_INFO_QUADRATURE_CORRECTION_RAW] = "quadrature_correction_raw",
 	[IIO_CHAN_INFO_AVERAGE_RAW] = "mean_raw",
+	[IIO_CHAN_INFO_LOW_PASS_FILTER_3DB_FREQUENCY]
+	= "filter_low_pass_3db_frequency",
 };
 
 /**