build: add KERNEL_MAKE and KERNEL_MAKE_FLAGS variables and move to kernel.mk

This allows packages to use kernel make options without the forced
-C $(LINUX_DIR). It also makes it more clear that it to be called from
kernel module packages directly.

Signed-off-by: Felix Fietkau <nbd@nbd.name>

include/kernel-build.mk

@@ -104,7 +104,7 @@ define BuildKernel
   $(KERNEL_BUILD_DIR)/symtab.h: FORCE
 	rm -f $(KERNEL_BUILD_DIR)/symtab.h
 	touch $(KERNEL_BUILD_DIR)/symtab.h
-	+$(MAKE) $(KERNEL_MAKEOPTS) vmlinux
+	+$(KERNEL_MAKE) vmlinux
 	find $(LINUX_DIR) $(STAGING_DIR_ROOT)/lib/modules -name \*.ko | \
 		xargs $(TARGET_CROSS)nm | \
 		awk '$$$$1 == "U" { print $$$$2 } ' | \
@@ -159,7 +159,7 @@ define BuildKernel
 	rm -f $(LINUX_DIR)/.config.prev
 	rm -f $(STAMP_CONFIGURED)
 	$(LINUX_RECONF_CMD) > $(LINUX_DIR)/.config
-	$(_SINGLE)$(MAKE) -C $(LINUX_DIR) $(KERNEL_MAKEOPTS) HOST_LOADLIBES="-L$(STAGING_DIR_HOST)/lib -lncurses" $$@
+	$(_SINGLE)$(KERNEL_MAKE) HOST_LOADLIBES="-L$(STAGING_DIR_HOST)/lib -lncurses" $$@
 	$(LINUX_RECONF_DIFF) $(LINUX_DIR)/.config > $(LINUX_RECONFIG_TARGET)
 
   install: $(LINUX_DIR)/.image

include/kernel-defaults.mk

@@ -11,27 +11,6 @@ ifneq ($(SOURCE_DATE_EPOCH),)
   endif
 endif
 
-KERNEL_MAKEOPTS := -C $(LINUX_DIR) \
-	HOSTCFLAGS="$(HOST_CFLAGS) -Wall -Wmissing-prototypes -Wstrict-prototypes" \
-	CROSS_COMPILE="$(KERNEL_CROSS)" \
-	ARCH="$(LINUX_KARCH)" \
-	KBUILD_HAVE_NLS=no \
-	KBUILD_BUILD_USER="$(call qstrip,$(CONFIG_KERNEL_BUILD_USER))" \
-	KBUILD_BUILD_HOST="$(call qstrip,$(CONFIG_KERNEL_BUILD_DOMAIN))" \
-	KBUILD_BUILD_TIMESTAMP="$(KBUILD_BUILD_TIMESTAMP)" \
-	KBUILD_BUILD_VERSION="0" \
-	HOST_LOADLIBES="-L$(STAGING_DIR_HOST)/lib" \
-	CONFIG_SHELL="$(BASH)" \
-	$(if $(findstring c,$(OPENWRT_VERBOSE)),V=1,V='') \
-	$(if $(PKG_BUILD_ID),LDFLAGS_MODULE=--build-id=0x$(PKG_BUILD_ID)) \
-	cmd_syscalls=
-
-
-ifeq ($(call qstrip,$(CONFIG_EXTERNAL_KERNEL_TREE))$(call qstrip,$(CONFIG_KERNEL_GIT_CLONE_URI)),)
-  KERNEL_MAKEOPTS += \
-	KERNELRELEASE=$(LINUX_VERSION)
-endif
-
 ifdef CONFIG_STRIP_KERNEL_EXPORTS
   KERNEL_MAKEOPTS += \
 	EXTRA_LDSFLAGS="-I$(KERNEL_BUILD_DIR) -include symtab.h"
@@ -43,10 +22,6 @@ ifneq (,$(KERNEL_CC))
   KERNEL_MAKEOPTS += CC="$(KERNEL_CC)"
 endif
 
-ifdef CONFIG_USE_SPARSE
-  KERNEL_MAKEOPTS += C=1 CHECK=$(STAGING_DIR_HOST)/bin/sparse
-endif
-
 export HOST_EXTRACFLAGS=-I$(STAGING_DIR_HOST)/include
 
 # defined in quilt.mk
@@ -127,7 +102,7 @@ define Kernel/Configure/Default
 		cp $(LINUX_DIR)/.config.set $(LINUX_DIR)/.config; \
 		cp $(LINUX_DIR)/.config.set $(LINUX_DIR)/.config.prev; \
 	}
-	$(_SINGLE) [ -d $(LINUX_DIR)/user_headers ] || $(MAKE) $(KERNEL_MAKEOPTS) INSTALL_HDR_PATH=$(LINUX_DIR)/user_headers headers_install
+	$(_SINGLE) [ -d $(LINUX_DIR)/user_headers ] || $(KERNEL_MAKE) INSTALL_HDR_PATH=$(LINUX_DIR)/user_headers headers_install
 	grep '=[ym]' $(LINUX_DIR)/.config.set | LC_ALL=C sort | mkhash md5 > $(LINUX_DIR)/.vermagic
 endef
 
@@ -137,7 +112,7 @@ endef
 
 define Kernel/CompileModules/Default
 	rm -f $(LINUX_DIR)/vmlinux $(LINUX_DIR)/System.map
-	+$(MAKE) $(KERNEL_MAKEOPTS) modules
+	+$(KERNEL_MAKE) modules
 endef
 
 OBJCOPY_STRIP = -R .reginfo -R .notes -R .note -R .comment -R .mdebug -R .note.gnu.build-id
@@ -161,7 +136,7 @@ endef
 
 define Kernel/CompileImage/Default
 	rm -f $(TARGET_DIR)/init
-	+$(MAKE) $(KERNEL_MAKEOPTS) $(if $(KERNELNAME),$(KERNELNAME),all) modules
+	+$(KERNEL_MAKE) $(if $(KERNELNAME),$(KERNELNAME),all) modules
 	$(call Kernel/CopyImage)
 endef
 
@@ -170,7 +145,7 @@ define Kernel/CompileImage/Initramfs
 	$(call Kernel/Configure/Initramfs)
 	$(CP) $(GENERIC_PLATFORM_DIR)/other-files/init $(TARGET_DIR)/init
 	rm -rf $(KERNEL_BUILD_DIR)/linux-$(LINUX_VERSION)/usr/initramfs_data.cpio*
-	+$(MAKE) $(KERNEL_MAKEOPTS) $(if $(KERNELNAME),$(KERNELNAME),all) modules
+	+$(KERNEL_MAKE) $(if $(KERNELNAME),$(KERNELNAME),all) modules
 	$(call Kernel/CopyImage,-initramfs)
 endef
 else

include/kernel.mk

@@ -87,6 +87,35 @@ else
   LINUX_KARCH := $(ARCH)
 endif
 
+KERNEL_MAKE = $(MAKE) $(KERNEL_MAKEOPTS)
+
+KERNEL_MAKE_FLAGS := \
+	HOSTCFLAGS="$(HOST_CFLAGS) -Wall -Wmissing-prototypes -Wstrict-prototypes" \
+	CROSS_COMPILE="$(KERNEL_CROSS)" \
+	ARCH="$(LINUX_KARCH)" \
+	KBUILD_HAVE_NLS=no \
+	KBUILD_BUILD_USER="$(call qstrip,$(CONFIG_KERNEL_BUILD_USER))" \
+	KBUILD_BUILD_HOST="$(call qstrip,$(CONFIG_KERNEL_BUILD_DOMAIN))" \
+	KBUILD_BUILD_TIMESTAMP="$(KBUILD_BUILD_TIMESTAMP)" \
+	KBUILD_BUILD_VERSION="0" \
+	HOST_LOADLIBES="-L$(STAGING_DIR_HOST)/lib" \
+	CONFIG_SHELL="$(BASH)" \
+	$(if $(findstring c,$(OPENWRT_VERBOSE)),V=1,V='') \
+	$(if $(PKG_BUILD_ID),LDFLAGS_MODULE=--build-id=0x$(PKG_BUILD_ID)) \
+	KERNELRELEASE=$(LINUX_VERSION) \
+	cmd_syscalls=
+
+ifeq ($(call qstrip,$(CONFIG_EXTERNAL_KERNEL_TREE))$(call qstrip,$(CONFIG_KERNEL_GIT_CLONE_URI)),)
+  KERNEL_MAKEOPTS += \
+	KERNELRELEASE=$(LINUX_VERSION)
+endif
+
+KERNEL_MAKEOPTS := -C $(LINUX_DIR) $(KERNEL_MAKE_FLAGS)
+
+ifdef CONFIG_USE_SPARSE
+  KERNEL_MAKEOPTS += C=1 CHECK=$(STAGING_DIR_HOST)/bin/sparse
+endif
+
 define KernelPackage/Defaults
   FILES:=
   AUTOLOAD:=

package/kernel/kmod-sched-cake/Makefile

@@ -36,7 +36,7 @@ define KernelPackage/sched-cake/description
 endef
 
 define Build/Compile
-	$(MAKE) $(KERNEL_MAKEOPTS) SUBDIRS="$(PKG_BUILD_DIR)" modules
+	$(KERNEL_MAKE) SUBDIRS="$(PKG_BUILD_DIR)" modules
 endef
 
 $(eval $(call KernelPackage,sched-cake))

package/kernel/trelay/Makefile

@@ -32,7 +32,7 @@ endef
 include $(INCLUDE_DIR)/kernel-defaults.mk
 
 define Build/Compile
-	$(MAKE) $(KERNEL_MAKEOPTS) SUBDIRS="$(PKG_BUILD_DIR)" modules
+	$(KERNEL_MAKE) SUBDIRS="$(PKG_BUILD_DIR)" modules
 endef
 
 define KernelPackage/trelay/conffiles