kbuild: introduce ccflags-y, asflags-y and ldflags-y

Introduce ccflags-y, asflags-y and ldflags-y so we soon can
deprecate use of EXTRA_CFLAGS, EXTRA_AFLAGS and EXTRA_LDFLAGS.
This patch does not touch any in-tree users - thats next round.
Lets get this committed first and then fix the users of the
soon to be deprecated variants next.

The rationale behind this change is to introduce support for
makefile fragments like:

ccflags-$(CONFIG_WHATEVER_DEBUG) := -DDEBUG

As a replacement for the uglier:
ifeq ($(CONFIG_WHATEVER_DEBUG),y)
        EXTRA_CFLAGS := -DDEBUG
endif

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

1 files changed, 18 insertions, 19 deletions

diff --git a/Documentation/kbuild/makefiles.txt b/Documentation/kbuild/makefiles.txt
index 08fbe6cd309d..f099b814d383 100644
--- a/Documentation/kbuild/makefiles.txt
+++ b/Documentation/kbuild/makefiles.txt
@@ -276,40 +276,39 @@ more details, with real examples.
 
 --- 3.7 Compilation flags
 
-    EXTRA_CFLAGS, EXTRA_AFLAGS, EXTRA_LDFLAGS
+    ccflags-y, asflags-y and ldflags-y
+        The three flags listed above applies only to the kbuild makefile
+        where they are assigned. They are used for all the normal
+        cc, as and ld invocation happenign during a recursive build.
+        Note: Flags with the same behaviour were previously named:
+        EXTRA_CFLAGS, EXTRA_AFLAGS and EXTRA_LDFLAGS.
+        They are yet supported but their use are deprecated.
 
-        All the EXTRA_ variables apply only to the kbuild makefile
-        where they are assigned. The EXTRA_ variables apply to all
-        commands executed in the kbuild makefile.
-
-        $(EXTRA_CFLAGS) specifies options for compiling C files with
-        $(CC).
+        ccflags-y specifies options for compiling C files with $(CC).
 
         Example:
                 # drivers/sound/emu10k1/Makefile
-                EXTRA_CFLAGS += -I$(obj)
-                ifdef DEBUG
-                    EXTRA_CFLAGS += -DEMU10K1_DEBUG
-                endif
+                ccflags-y += -I$(obj)
+                ccflags-$(DEBUG) += -DEMU10K1_DEBUG
 
 
         This variable is necessary because the top Makefile owns the
         variable $(KBUILD_CFLAGS) and uses it for compilation flags for the
         entire tree.
 
-        $(EXTRA_AFLAGS) is a similar string for per-directory options
+        asflags-y is a similar string for per-directory options
         when compiling assembly language source.
 
         Example:
                 #arch/x86_64/kernel/Makefile
-                EXTRA_AFLAGS := -traditional
+                asflags-y := -traditional
 
 
-        $(EXTRA_LDFLAGS) is a string for per-directory options to $(LD).
+        ldflags-y is a string for per-directory options to $(LD).
 
         Example:
                 #arch/m68k/fpsp040/Makefile
-                EXTRA_LDFLAGS := -x
+                ldflags-y := -x
 
     CFLAGS_$@, AFLAGS_$@
 
@@ -495,9 +494,9 @@ more details, with real examples.
 
         Example:
                 #fs/reiserfs/Makefile
-                EXTRA_CFLAGS := $(call cc-ifversion, -lt, 0402, -O1)
+                ccflags-y := $(call cc-ifversion, -lt, 0402, -O1)
 
-        In this example, EXTRA_CFLAGS will be assigned the value -O1 if the
+        In this example, ccflags-y will be assigned the value -O1 if the
         $(CC) version is less than 4.2.
         cc-ifversion takes all the shell operators:
         -eq, -ne, -lt, -le, -gt, and -ge
@@ -783,7 +782,7 @@ When kbuild executes, the following steps are followed (roughly):
         Example:
                 #arch/s390/Makefile
                 LDFLAGS         := -m elf_s390
-        Note: EXTRA_LDFLAGS can be used to further customise
+        Note: ldflags-y can be used to further customise
         the flags used. See chapter 3.7.
 
     LDFLAGS_MODULE      Options for $(LD) when linking modules
@@ -1100,7 +1099,7 @@ When kbuild executes, the following steps are followed (roughly):
 
         When building the *.lds target, kbuild uses the variables:
         KBUILD_CPPFLAGS : Set in top-level Makefile
-        EXTRA_CPPFLAGS  : May be set in the kbuild makefile
+        cppflags-y      : May be set in the kbuild makefile
         CPPFLAGS_$(@F)  : Target specific flags.
                           Note that the full filename is used in this
                           assignment.