Here is an example of a Makefile for a kernel module.
the important thing here to note is that the dots shown below must be replaced by a TAB, replacing them by spaces will cause Makefile to malfunction.
obj-m += hello.o
all:
.......make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules
clean:
.......make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean