staging: comedi: introduce comedi_range_is_{bi,uni}polar()

Introduce some helper functions to check if a given 'range' index
to a comedi_subdevice 'range_table' is a bipolar or unipolar range.
Signed-off-by: NH Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/comedi/comedidev.h

@@ -307,6 +307,18 @@ struct comedi_lrange {
 	struct comedi_krange range[GCC_ZERO_LENGTH_ARRAY];
 };
 
+static inline bool comedi_range_is_bipolar(struct comedi_subdevice *s,
+					   unsigned int range)
+{
+	return s->range_table->range[range].min < 0;
+}
+
+static inline bool comedi_range_is_unipolar(struct comedi_subdevice *s,
+					    unsigned int range)
+{
+	return s->range_table->range[range].min >= 0;
+}
+
 /* some silly little inline functions */
 
 static inline unsigned int bytes_per_sample(const struct comedi_subdevice *subd)