[HOWTO] set extra_cflags to indicate compilation against -mm kernels

[Michael Krufky]

With the addition of topdir-mm.patch into the -mm tree (since 
2.6.13-rc3-mm2), it is now possible for Makefile to detect whether a cvs 
subtree is being built against -mm or not...  -mm kernels now have a .mm 
file in the top level directory.

inside Makefile:

mm-kernel := $(TOPDIR)/.mm
ifneq ($(mm-kernel),)
MM_KERNEL_CFLAGS	:= -DMM_KERNEL=$(shell cat $(mm-kernel) 2> /dev/null)
ifneq ($(MM_KERNEL_CFLAGS),-DMM_KERNEL=)
EXTRA_CFLAGS		+= $(MM_KERNEL_CFLAGS)
endif
endif


inside C files:
#ifdef MM_KERNEL
/* code needed by -mm kernel only */
#else
/* original code for compilation against -linus */
#endif


This should probably be documented somewhere, but I don't know where it 
goes.......

--
Michael Krufky

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