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

[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

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

[Sam Ravnborg]

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 $(mm-kernel) 2> /dev/null)
> ifneq ($(MM_KERNEL_CFLAGS),-DMM_KERNEL=)
> EXTRA_CFLAGS		+= $(MM_KERNEL_CFLAGS)
> endif
> endif

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.

	Sam

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

[Michael Krufky]

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

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