How to pass flag from makefile to preprocesor when building external kernel module

Hi
I have problem with passing flag from makefile to .c file.
During building external kernel module my macro isn't seen by compiler. I
used plenty of ways.

First way:
ccflags-y += -DMY_FLAG
$(MAKE) -C $(KERNEL_SRC) M=$(SRC)
Second:
$(MAKE) -C $(KERNEL_SRC) M=$(SRC) CFLAGS_my-kernel-module.o="-DMY_FLAG"
Third:
$(MAKE) -C $(KERNEL_SRC) M=$(SRC) CFLAGS="-DMY_FLAG"
Forth:
 $(MAKE) -C $(KERNEL_SRC) M=$(SRC) ccflags-y="-DMY_FLAG"

In general I use bitbake to build external kernel modules.  And I wonder if
bitbake doesn't introduce issue as some of above solution really should
work. And additionally I had to use absolute paths in headers because
relative didn't work so -I append also doesn't work:
SRC := $(shell pwd)
ccflags-y := -I$(SRC)

BR
Tomek