[RFC PATCH 2/5] Add CONFIG symbol to module as compilation parameter

[Cristina Moraru <cristina.moraru09@gmail.com>]

Add CONFIG symbol to kernel modules as a define via -D
compilation parameter. The CONFIG_FOO symbol for each
module is determined by the module name, using the
associations from Module.ksymb. This file is loaded
using the 'include' directive, thus run like a regular
makefile. The format of the content of the file is the
following:

foo_KCONF=CONFIG_FOO

creating a set of Makefile variables foo_KCONF with the
CONFIG_FOO as values.

The Makefile then adds this value in the compilation
command with -DKBUILD_KCONF='"CONFIG_FOO"'.

This patch is part of a research project within
Google Summer of Code of porting 'make localmodconfig'
for backported drivers. The goal is to enable each
module to expose in /sys its corresponding CONFIG_* option.
The value of this attribute will be dynamically pegged by
modpost without requiring extra work from the driver developers.
Further, this information will be used by a hardware interogation
tool to extract build information about the existing devices.

Signed-off-by: Cristina Moraru <cristina.moraru09@gmail.com>
---
 scripts/Makefile.lib | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index e7df0f5..8ae9b7f 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -89,6 +89,10 @@ multi-objs-m	:= $(addprefix $(obj)/,$(multi-objs-m))
 subdir-ym	:= $(addprefix $(obj)/,$(subdir-ym))
 obj-dirs	:= $(addprefix $(obj)/,$(obj-dirs))
 
+# Include Module.ksymb which contains the associations of modules' names
+# and corresponding CONFIG_* options
+include Module.ksymb
+
 # These flags are needed for modversions and compiling, so we define them here
 # already
 # $(modname_flags) #defines KBUILD_MODNAME as the name of the module it will
@@ -100,6 +104,9 @@ name-fix = $(squote)$(quote)$(subst $(comma),_,$(subst -,_,$1))$(quote)$(squote)
 basename_flags = -DKBUILD_BASENAME=$(call name-fix,$(basetarget))
 modname_flags  = $(if $(filter 1,$(words $(modname))),\
                  -DKBUILD_MODNAME=$(call name-fix,$(modname)))
+ksym-fix = $(squote)$(quote)$($(subst $(comma),_,$(subst -,_,$1))_KCONF)$(quote)$(squote)
+ksymb_flags = $(if $(filter 1,$(words $(modname))),\
+                 -DKBUILD_KSYMB=$(call ksym-fix, $(modname)))
 
 orig_c_flags   = $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS) $(KBUILD_SUBDIR_CCFLAGS) \
                  $(ccflags-y) $(CFLAGS_$(basetarget).o)
@@ -162,7 +169,7 @@ endif
 
 c_flags        = -Wp,-MD,$(depfile) $(NOSTDINC_FLAGS) $(LINUXINCLUDE)     \
 		 $(__c_flags) $(modkern_cflags)                           \
-		 $(basename_flags) $(modname_flags)
+		 $(basename_flags) $(modname_flags) $(ksymb_flags)
 
 a_flags        = -Wp,-MD,$(depfile) $(NOSTDINC_FLAGS) $(LINUXINCLUDE)     \
 		 $(__a_flags) $(modkern_aflags)
-- 
2.7.4