Problem in loading module of Software trigger

[SIMRAN SINGHAL]

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)