Compile Warning - ARM Cross Compiler

Question

I have been trying to cross compile a loadable kernel module and I have been getting warning message that I would like to get help.

Below is the warning message

make[1]: Entering directory `/home/userid/rowboat-android/kernel'
   Building modules, stage 2.
   MODPOST 1 modules
WARNING: "omap_device_build" [/home/userid/myfiles/lcdc_load_device.ko] undefined!
WARNING: "omap_hwmod_lookup" [/home/userid/myfiles/lcdc_load_device.ko] undefined!
make[1]: Leaving directory `/home/userid/rowboat-android/kernel'

Below is the Makefile

obj-m :=lcdc_load_device.o
lcdc_load_device-m := ../rowboat-android/kernel/arch/arm/plat-omap/omap_device.o
lcdc_load_device-m += ../rowboat-android/kernel/arch/arm/mach-omap2/omap_hwmod.o

ccflags-m := -I$(src)/../rowboat-android/kernel/arch/arm/plat-omap/include/plat/

KDIR := /home/userid/rowboat-android/kernel/
PWD := $(shell pwd)

default:
   $(MAKE) ARCH=arm CROSS_COMPILE=/home/userid/rowboat-android/prebuilt/linux-x86/toolchain/arm-eabi-4.4.3/bin/arm-eabi- -C $(KDIR) SUBDIRS=$(PWD) modules

clean:
   $(MAKE) -C $(KDIR) SUBDIRS=$(PWD) clean

I am suspecting that the makefile is finding the header file for "omap_device_build" and "omap_hwmod_lookup" functions.

Appreciate your help, and thank you advance.

Answer 1

Thank you to mbratch and artless noise for their comments

To address the WARNINGS, the symbols need to be exported. For the above question place

EXPORT_SYMBOL(omap_device_build) in omap_device.c 
EXPORT_SYMBOL(omap_hwmod_lookup) in omap_hwmod.c

and compile the kernel. Then compile the loadable kernel module against the compiled kernel. Perform the following to verify if the symbols have been exported

grep omap_device_build /proc/kallsyms
or
grep omap_device_build Module.symvers

For more details reference the following links

• Kernel Symbols: What's available to Your Module
• Building and Running Modules

Comments are welcome

Thank you