Re: introduce arch/$ARCH/Kbuild ?

[Sam Ravnborg <sam@ravnborg.org>]

> 
> Most of arch/mips uses -Werror these days and while painful at times it
> keeps everybody on their toes hopefully cleaner, less buggy code.  So if
> your solution allows adding -Werror to all subdirs automatically with
> a mechanism to remove -Werror from a few selected dirs then I'm interested.

It is already present in mainline - so go wild.

I took a look at mips.
mips supports an impressive amount of platform/boards.
The has resulted in lines like the following in the arch Makefile:

core-$(CONFIG_SGI_IP32)         += arch/mips/sgi-ip32/
cflags-$(CONFIG_SGI_IP32)       += -I$(srctree)/arch/mips/include/asm/mach-ip32
load-$(CONFIG_SGI_IP32)         += 0xffffffff80004000

But this is less then optimal. If two people add a paltform you will
have a merge issue.
And centralize information like that is also questionable.

mips would be better suited if you had all sgi_ip32 information located
in a single directory.

How about a setup like this:

arch/mips/sgi_ip32/Platform:
platfrom-y                      += arch/mips/sgi-ip32/
cflags-$(CONFIG_SGI_IP32)       += -I$(srctree)/arch/mips/include/asm/mach-ip32
load-$(CONFIG_SGI_IP32)         += 0xffffffff80004000


arch/mips/Kbuild.platforms:
#All platforms listed in alphabetic order
platforms-y += lasat/
platforms-y += sgi_ip32/

#include the platform specific files
include $(patsubst %, arch/misp/%Platform)


arch/mips/Kbuild:
subdir-ccflags-y := -Werror

include arch/mips/Kbuild.platforms
obj-y += $(platform-y)

obj-y +=  arch/mips/kernel/ arch/mips/mm/ arch/mips/math-emu/


arch/mips/Makefile:
core-y += arch/mips/
include arch/mips/Kbuild.platforms



The above does a few things:
1) It decentralize the plaform stuff (to the Platform files)
2) In troduces a arch/mips/Kbuild file that specify everything
   that is linked in as core-y
3) It adds a single subdir-ccflags-y := -Werror that covers
   all platforms and the core part of the kernel
   (Everything specified in arch/mips/Kbuild)
4) It reuses Kbuild.platforms in Kbuild and
   in Makefile.
   In Makefile it is used to find ccflags-y
   and load-y definitions.
   In Kbuild it is used to find the objects to add to obj-y.


The above is entirely untested - but I hope to have adressed the principles.

	Sam