Re: [HOWTO] set extra_cflags to indicate compilation against -mmkernels

From: Michael Krufky
Date: Sun Jul 31 2005 - 09:06:49 EST

Sam Ravnborg wrote:

On Sat, Jul 30, 2005 at 05:29:21PM -0400, Michael Krufky wrote:

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)

Hi Michael.
The content of the .mm file seems to be insignificant - '1'. The important
issue is that the file is present.
Also please do not use $(TOPDIR) - it is deprecated.

The following is enough:
EXTRA_CFLAGS += $(if $(wildcard $(srctree)/.mm), -DMM_KERNEL)

If the file exist in the root of the kernel src tree MM_KERNEL will be
added to EXTRA_CFLAGS.


Thank you! I knew there might be a more efficient way to do that, so I'm glad I sent that to LKML for you to see ;-)

Still, I think it should be added into the documentation somewhere... I'd be happy to submit a patch, I just don't know where it should go. Obviously, this is specific to -mm kernels only. Do you know?

Michael Krufky

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