Currently source files in the Documentation/ sub-dir can easily bit-rot
since they are not generally buildable, either because they are hidden in
text files or because there are no Makefile rules for them.  This needs to
be fixed so that the source files remain usable and good examples of code
instead of bad examples.

Add the ability to build source files that are in the Documentation/ dir.
Add to Kconfig as "BUILD_DOCSRC" config symbol.

Use "CONFIG_BUILD_DOCSRC=1 make ..." to build objects from the
Documentation/ sources.  Or enable BUILD_DOCSRC in the *config system.
However, this symbol depends on HEADERS_CHECK since the header files need
to be installed (for userspace builds).

Built (using cross-tools) for x86-64, i386, alpha, ia64, sparc32,
sparc64, powerpc, sh, m68k, & mips.

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

It's a problem about cscope target of kernel Makefile, and the cscope
plugin of emacs:
1. `make cscope` will generate cscope.files cscope.{in,po,}.out;
2. the cscope plugin expect a cscope.out.{in,po,};
3. the default `cscope -b` would generate cscope.{in,po,}.out;

There are three approach to solve it:
1. modify the cscope C code;
2. modify the cscope emacs plugin lisp code;
3. modify the Makefile;

I have tried to communicate with the cscope upstream, but later I
realize the third approach is most meaningful.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

With a make O=... build kbuild would only create
the include2/asm symlink for archs that not yet
had moved headers to include/$ARCH/include

There is no longer any reason to avoid the symlink
for archs that has moved their headers so create it
unconditionally.

This fixes arm because kbuild checked for include/asm-$ARCH/errno.h
and that file was not present for arm but the platform files
are not yet moved.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Russell King <rmk@arm.linux.org.uk>

We used include/asm-$ARCH/system.h to check if
we should create a symlink in include2 directory with
make O=... builds.
But um does not have such a file thus build filed.

Let's try anohter filename:
$ ls -d include/asm-* | wc -l
21
$ ls -d include/asm-*/errno.h | wc -l
21

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Jeff Dike <jdike@addtoit.com>

The majority of this patch was created by the following script:

***
ASM=arch/sparc/include/asm
mkdir -p $ASM
git mv include/asm-sparc64/ftrace.h $ASM
git rm include/asm-sparc64/*
git mv include/asm-sparc/* $ASM
sed -ie 's/asm-sparc64/asm/g' $ASM/*
sed -ie 's/asm-sparc/asm/g' $ASM/*
***

The rest was an update of the top-level Makefile to use sparc
for header files when sparc64 is being build.
And a small fixlet to pick up the correct unistd.h from
sparc64 code.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

* git://git.kernel.org/pub/scm/linux/kernel/git/sam/kbuild-next: (25 commits)
  setlocalversion: do not describe if there is nothing to describe
  kconfig: fix typos: "Suport" -> "Support"
  kconfig: make defconfig is no longer chatty
  kconfig: make oldconfig is now less chatty
  kconfig: speed up all*config + randconfig
  kconfig: set all new symbols automatically
  kconfig: add diffconfig utility
  kbuild: remove Module.markers during mrproper
  kbuild: sparse needs CF not CHECKFLAGS
  kernel-doc: handle/strip __init
  vmlinux.lds: move __attribute__((__cold__)) functions back into final .text section
  init: fix URL of "The GNU Accounting Utilities"
  kbuild: add arch/$ARCH/include to search path
  kbuild: asm symlink support for arch/$ARCH/include
  kbuild: support arch/$ARCH/include for tags, cscope
  kbuild: prepare headers_* for arch/$ARCH/include
  kbuild: install all headers when arch is changed
  kbuild: make clean removes *.o.* as well
  kbuild: optimize headers_* targets
  kbuild: only one call for include/ in make headers_*
  ...