kbuild: separate kerneldoc warnings from compiler warnings

[Valdis KlÄtnieks]

This patch introduces a new build flag 'K=1' which controls whether kerneldoc
warnings should be issued, separating them from the compiler warnings that W=
controls.

Signed-off-by: Valdis Kletnieks <valdis.kletnieks@xxxxxx>

diff --git a/Makefile b/Makefile
index 29abe44ada91..b1c0f9484a66 100644
--- a/Makefile
+++ b/Makefile
@@ -1605,6 +1605,7 @@ PHONY += help
 	@echo  '                       (sparse by default)'
 	@echo  '  make C=2   [targets] Force check of all c source with $$CHECK'
 	@echo  '  make RECORDMCOUNT_WARN=1 [targets] Warn about ignored mcount sections'
+	@echo  '  make K=1   [targets] Warn about problems in kerneldoc comments'
 	@echo  '  make W=n   [targets] Enable extra build checks, n=1,2,3 where'
 	@echo  '		1: warnings which may be relevant and do not occur too often'
 	@echo  '		2: warnings which occur quite often but may still be relevant'
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 2e8810b7e5ed..9bcb77f5a5f1 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -100,7 +100,7 @@ else ifeq ($(KBUILD_CHECKSRC),2)
         cmd_force_checksrc = $(CHECK) $(CHECKFLAGS) $(c_flags) $<
 endif
 
-ifneq ($(KBUILD_EXTRA_WARN),)
+ifneq ($(KBUILD_KDOC_WARN),)
   cmd_checkdoc = $(srctree)/scripts/kernel-doc -none $<
 endif
 
diff --git a/scripts/Makefile.extrawarn b/scripts/Makefile.extrawarn
index 4aea7cf71d11..3fd5881c91b0 100644
--- a/scripts/Makefile.extrawarn
+++ b/scripts/Makefile.extrawarn
@@ -17,6 +17,12 @@ endif
 
 export KBUILD_EXTRA_WARN
 
+ifeq ("$(origin K)", "command line")
+  KBUILD_KDOC_WARN := $(K)
+endif
+
+export KBUILD_KDOC_WARN
+
 #
 # W=1 - warnings which may be relevant and do not occur too often
 #