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