Problem in loading module of Software trigger

I read this documentation "Documentation/iio/iio_configfs.txt" for creating software trigger. So, by following this I created the module with name iio-trig-sample.c in drivers/iio/trigger/. iio-trigger-sample.c also compiled successfully. Now, when I tried to insert module: $ sudo insmod iio-trig-sample.ko insmod: ERROR: could not insert module iio-trig-sample.ko: Unknown symbol in module Ans in /var/log/kern.log: I am getting following reason:- iio_trig_sample: Unknown symbol iio_unregister_sw_trigger_type (err 0) iio_trig_sample: Unknown symbol iio_register_sw_trigger_type (err 0)