u-boot/scripts/Makefile.spl

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#
# (C) Copyright 2000-2011
# Wolfgang Denk, DENX Software Engineering, wd@denx.de.
#
# (C) Copyright 2011
# Daniel Schwierzeck, daniel.schwierzeck@googlemail.com.
#
# (C) Copyright 2011
# Texas Instruments Incorporated - http://www.ti.com/
# Aneesh V <aneesh@ti.com>
#
# SPDX-License-Identifier: GPL-2.0+
#
# Based on top-level Makefile.
#
src := $(obj)
# Create output directory if not already present
_dummy := $(shell [ -d $(obj) ] || mkdir -p $(obj))
include $(srctree)/scripts/Kbuild.include
kconfig: switch to single .config configuration When Kconfig for U-boot was examined, one of the biggest issues was how to support multiple images (Normal, SPL, TPL). There were actually two options, "single .config" and "multiple .config". After some discussions and thought experiments, I chose the latter, i.e. to create ".config", "spl/.config", "tpl/.config" for Normal, SPL, TPL, respectively. It is true that the "multiple .config" strategy provided us the maximum flexibility and helped to avoid duplicating CONFIGs among Normal, SPL, TPL, but I have noticed some fatal problems: [1] It is impossible to share CONFIG options across the images. If you change the configuration of Main image, you often have to adjust some SPL configurations correspondingly. Currently, we cannot handle the dependencies between them. It means one of the biggest advantages of Kconfig is lost. [2] It is too painful to change both ".config" and "spl/.config". Sunxi guys started to work around this problem by creating a new configuration target. Commit cbdd9a9737cc (sunxi: kconfig: Add %_felconfig rule to enable FEL build of sunxi platforms.) added "make *_felconfig" to enable CONFIG_SPL_FEL on both images. Changing the configuration of multiple images in one command is a generic demand. The current implementation cannot propose any good solution about this. [3] Kconfig files are getting ugly and difficult to understand. Commit b724bd7d6349 (dm: Kconfig: Move CONFIG_SYS_MALLOC_F_LEN to Kconfig) has sprinkled "if !SPL_BUILD" over the Kconfig files. [4] The build system got more complicated than it should be. To adjust Linux-originated Kconfig to U-Boot, the helper script "scripts/multiconfig.sh" was introduced. Writing a complicated text processor is a shell script sometimes caused problems. Now I believe the "single .config" will serve us better. With it, all the problems above would go away. Instead, we will have to add some CONFIG_SPL_* (and CONFIG_TPL_*) options such as CONFIG_SPL_DM, but we will not have much. Anyway, this is what we do now in scripts/Makefile.spl. I admit my mistake with my apology and this commit switches to the single .config configuration. It is not so difficult to do that: - Remove unnecessary processings from scripts/multiconfig.sh This file will remain for a while to support the current defconfig format. It will be removed after more cleanups are done. - Adjust some makefiles and Kconfigs - Add some entries to include/config_uncmd_spl.h and the new file scripts/Makefile.uncmd_spl. Some CONFIG options that are not supported on SPL must be disabled because one .config is shared between SPL and U-Boot proper going forward. I know this is not a beautiful solution and I think we can do better, but let's see how much we will have to describe them. - update doc/README.kconfig More cleaning up patches will follow this. Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com> Reviewed-by: Simon Glass <sjg@chromium.org>
2015-02-24 13:26:20 +00:00
-include include/config/auto.conf
kconfig: switch to Kconfig This commit enables Kconfig. Going forward, we use Kconfig for the board configuration. mkconfig will never be used. Nor will include/config.mk be generated. Kconfig must be adjusted for U-Boot because our situation is a little more complicated than Linux Kernel. We have to generate multiple boot images (Normal, SPL, TPL) from one source tree. Each image needs its own configuration input. Usage: Run "make <board>_defconfig" to do the board configuration. It will create the .config file and additionally spl/.config, tpl/.config if SPL, TPL is enabled, respectively. You can use "make config", "make menuconfig" etc. to create a new .config or modify the existing one. Use "make spl/config", "make spl/menuconfig" etc. for spl/.config and do likewise for tpl/.config file. The generic syntax of configuration targets for SPL, TPL is: <target_image>/<config_command> Here, <target_image> is either 'spl' or 'tpl' <config_command> is 'config', 'menuconfig', 'xconfig', etc. When the configuration is done, run "make". (Or "make <board>_defconfig all" will do the configuration and build in one time.) For futher information of how Kconfig works in U-Boot, please read the comment block of scripts/multiconfig.py. By the way, there is another item worth remarking here: coexistence of Kconfig and board herder files. Prior to Kconfig, we used C headers to define a set of configs. We expect a very long term to migrate from C headers to Kconfig. Two different infractructure must coexist in the interim. In our former configuration scheme, include/autoconf.mk was generated for use in makefiles. It is still generated under include/, spl/include/, tpl/include/ directory for the Normal, SPL, TPL image, respectively. Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com> Acked-by: Simon Glass <sjg@chromium.org>
2014-07-30 05:08:17 +00:00
-include $(obj)/include/autoconf.mk
kconfig: switch to single .config configuration When Kconfig for U-boot was examined, one of the biggest issues was how to support multiple images (Normal, SPL, TPL). There were actually two options, "single .config" and "multiple .config". After some discussions and thought experiments, I chose the latter, i.e. to create ".config", "spl/.config", "tpl/.config" for Normal, SPL, TPL, respectively. It is true that the "multiple .config" strategy provided us the maximum flexibility and helped to avoid duplicating CONFIGs among Normal, SPL, TPL, but I have noticed some fatal problems: [1] It is impossible to share CONFIG options across the images. If you change the configuration of Main image, you often have to adjust some SPL configurations correspondingly. Currently, we cannot handle the dependencies between them. It means one of the biggest advantages of Kconfig is lost. [2] It is too painful to change both ".config" and "spl/.config". Sunxi guys started to work around this problem by creating a new configuration target. Commit cbdd9a9737cc (sunxi: kconfig: Add %_felconfig rule to enable FEL build of sunxi platforms.) added "make *_felconfig" to enable CONFIG_SPL_FEL on both images. Changing the configuration of multiple images in one command is a generic demand. The current implementation cannot propose any good solution about this. [3] Kconfig files are getting ugly and difficult to understand. Commit b724bd7d6349 (dm: Kconfig: Move CONFIG_SYS_MALLOC_F_LEN to Kconfig) has sprinkled "if !SPL_BUILD" over the Kconfig files. [4] The build system got more complicated than it should be. To adjust Linux-originated Kconfig to U-Boot, the helper script "scripts/multiconfig.sh" was introduced. Writing a complicated text processor is a shell script sometimes caused problems. Now I believe the "single .config" will serve us better. With it, all the problems above would go away. Instead, we will have to add some CONFIG_SPL_* (and CONFIG_TPL_*) options such as CONFIG_SPL_DM, but we will not have much. Anyway, this is what we do now in scripts/Makefile.spl. I admit my mistake with my apology and this commit switches to the single .config configuration. It is not so difficult to do that: - Remove unnecessary processings from scripts/multiconfig.sh This file will remain for a while to support the current defconfig format. It will be removed after more cleanups are done. - Adjust some makefiles and Kconfigs - Add some entries to include/config_uncmd_spl.h and the new file scripts/Makefile.uncmd_spl. Some CONFIG options that are not supported on SPL must be disabled because one .config is shared between SPL and U-Boot proper going forward. I know this is not a beautiful solution and I think we can do better, but let's see how much we will have to describe them. - update doc/README.kconfig More cleaning up patches will follow this. Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com> Reviewed-by: Simon Glass <sjg@chromium.org>
2015-02-24 13:26:20 +00:00
KBUILD_CPPFLAGS += -DCONFIG_SPL_BUILD
ifeq ($(CONFIG_TPL_BUILD),y)
KBUILD_CPPFLAGS += -DCONFIG_TPL_BUILD
endif
ifeq ($(CONFIG_TPL_BUILD),y)
SPL_BIN := u-boot-tpl
else
SPL_BIN := u-boot-spl
endif
include $(srctree)/config.mk
include $(srctree)/arch/$(ARCH)/Makefile
kbuild: improve Kbuild speed Kbuild brought about many advantages for us but a significant performance regression was reported by Simon Glass. After some discussions and analysis, it turned out its main cause is in $(call cc-option,...). Historically, U-Boot parses all config.mk (arch/*/config.mk and board/*/config.mk) every time descending into subdirectories. That means cc-options are evaluated over and over again. $(call cc-option,...) is useful but costly. So we want to evaluate them only in ./Makefile and spl/Makefile and export compiler flags. This commit changes the build system as follows: - Modify scripts/Makefile.build to not include config.mk Instead, add $(PLATFORM_CPPFLAGS) to asflags-y, ccflags-y, cppflags-y. - Export many variables Going forward, Kbuild will not parse config.mk files when it descends into subdirectories. If we want to set variables in config.mk and use them in subdirectories, they must be exported. This is the list of variables to get exported: PLATFORM_CPPFLAGS CPUDIR BOARDDIR OBJCOPYFLAGS LDFLAGS LDFLAGS_FINAL (used in nand_spl/board/*/*/Makefile) CONFIG_STANDALONE_LOAD_ADDR (used in examples/standalone/Makefile) SYM_PREFIX (used in examples/standalone/Makefile) RELFLAGS (used in examples/standalone/Makefile) - Delete CPPFLAGS This variable has been replaced with PLATFORM_CPPFLAGS - Copy gcclibdir from example/standalone/Makefile to arch/sparc/config.mk The reference in CONFIG_STANDALONE_LOAD_ADDR must be resolved before it is exported. Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com> Reported-by: Simon Glass <sjg@chromium.org> Acked-by: Simon Glass <sjg@chromium.org> Tested-by: Simon Glass <sjg@chromium.org> [on Sandbox] Tested-by: Stephen Warren <swarren@nvidia.com> [on Tegra]
2014-03-05 07:59:40 +00:00
# Enable garbage collection of un-used sections for SPL
KBUILD_CFLAGS += -ffunction-sections -fdata-sections
LDFLAGS_FINAL += --gc-sections
# FIX ME
kbuild: improve Kbuild speed Kbuild brought about many advantages for us but a significant performance regression was reported by Simon Glass. After some discussions and analysis, it turned out its main cause is in $(call cc-option,...). Historically, U-Boot parses all config.mk (arch/*/config.mk and board/*/config.mk) every time descending into subdirectories. That means cc-options are evaluated over and over again. $(call cc-option,...) is useful but costly. So we want to evaluate them only in ./Makefile and spl/Makefile and export compiler flags. This commit changes the build system as follows: - Modify scripts/Makefile.build to not include config.mk Instead, add $(PLATFORM_CPPFLAGS) to asflags-y, ccflags-y, cppflags-y. - Export many variables Going forward, Kbuild will not parse config.mk files when it descends into subdirectories. If we want to set variables in config.mk and use them in subdirectories, they must be exported. This is the list of variables to get exported: PLATFORM_CPPFLAGS CPUDIR BOARDDIR OBJCOPYFLAGS LDFLAGS LDFLAGS_FINAL (used in nand_spl/board/*/*/Makefile) CONFIG_STANDALONE_LOAD_ADDR (used in examples/standalone/Makefile) SYM_PREFIX (used in examples/standalone/Makefile) RELFLAGS (used in examples/standalone/Makefile) - Delete CPPFLAGS This variable has been replaced with PLATFORM_CPPFLAGS - Copy gcclibdir from example/standalone/Makefile to arch/sparc/config.mk The reference in CONFIG_STANDALONE_LOAD_ADDR must be resolved before it is exported. Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com> Reported-by: Simon Glass <sjg@chromium.org> Acked-by: Simon Glass <sjg@chromium.org> Tested-by: Simon Glass <sjg@chromium.org> [on Sandbox] Tested-by: Stephen Warren <swarren@nvidia.com> [on Tegra]
2014-03-05 07:59:40 +00:00
cpp_flags := $(KBUILD_CPPFLAGS) $(PLATFORM_CPPFLAGS) $(UBOOTINCLUDE) \
$(NOSTDINC_FLAGS)
HAVE_VENDOR_COMMON_LIB = $(if $(wildcard $(srctree)/board/$(VENDOR)/common/Makefile),y,n)
libs-y += $(if $(BOARDDIR),board/$(BOARDDIR)/)
libs-$(HAVE_VENDOR_COMMON_LIB) += board/$(VENDOR)/common/
libs-$(CONFIG_SPL_FRAMEWORK) += common/spl/
libs-$(CONFIG_SPL_LIBCOMMON_SUPPORT) += common/
libs-$(CONFIG_SPL_LIBDISK_SUPPORT) += disk/
libs-$(CONFIG_SPL_DM) += drivers/core/
libs-$(CONFIG_SPL_I2C_SUPPORT) += drivers/i2c/
libs-$(CONFIG_SPL_GPIO_SUPPORT) += drivers/gpio/
libs-$(CONFIG_SPL_MMC_SUPPORT) += drivers/mmc/
libs-$(CONFIG_SPL_MPC8XXX_INIT_DDR_SUPPORT) += drivers/ddr/fsl/
libs-$(CONFIG_SYS_MVEBU_DDR) += drivers/ddr/mvebu/
libs-$(CONFIG_SPL_SERIAL_SUPPORT) += drivers/serial/
libs-$(CONFIG_SPL_SPI_FLASH_SUPPORT) += drivers/mtd/spi/
libs-$(CONFIG_SPL_SPI_SUPPORT) += drivers/spi/
libs-y += fs/
libs-$(CONFIG_SPL_LED_SUPPORT) += drivers/led/
libs-$(CONFIG_SPL_LIBGENERIC_SUPPORT) += lib/
libs-$(CONFIG_SPL_POWER_SUPPORT) += drivers/power/ drivers/power/pmic/
libs-$(CONFIG_SPL_POWER_SUPPORT) += drivers/power/regulator/
libs-$(CONFIG_SPL_MTD_SUPPORT) += drivers/mtd/
libs-$(CONFIG_SPL_NAND_SUPPORT) += drivers/mtd/nand/
libs-$(CONFIG_SPL_DRIVERS_MISC_SUPPORT) += drivers/misc/
libs-$(CONFIG_SPL_ONENAND_SUPPORT) += drivers/mtd/onenand/
libs-$(CONFIG_SPL_DMA_SUPPORT) += drivers/dma/
libs-$(CONFIG_SPL_POST_MEM_SUPPORT) += post/drivers/
libs-$(CONFIG_SPL_NET_SUPPORT) += net/
libs-$(CONFIG_SPL_ETH_SUPPORT) += drivers/net/
libs-$(CONFIG_SPL_ETH_SUPPORT) += drivers/net/phy/
libs-$(CONFIG_SPL_USBETH_SUPPORT) += drivers/net/phy/
libs-$(CONFIG_SPL_RAM_SUPPORT) += drivers/ram/
libs-$(CONFIG_SPL_MUSB_NEW_SUPPORT) += drivers/usb/musb-new/
libs-$(CONFIG_SPL_USBETH_SUPPORT) += drivers/usb/gadget/
libs-$(CONFIG_SPL_WATCHDOG_SUPPORT) += drivers/watchdog/
libs-$(CONFIG_SPL_USB_HOST_SUPPORT) += drivers/usb/host/
libs-$(CONFIG_OMAP_USB_PHY) += drivers/usb/phy/
libs-$(CONFIG_SPL_SATA_SUPPORT) += drivers/block/
head-y := $(addprefix $(obj)/,$(head-y))
libs-y := $(addprefix $(obj)/,$(libs-y))
u-boot-spl-dirs := $(patsubst %/,%,$(filter %/, $(libs-y)))
libs-y := $(patsubst %/, %/built-in.o, $(libs-y))
# Add GCC lib
ifeq ($(CONFIG_USE_PRIVATE_LIBGCC),y)
PLATFORM_LIBGCC = arch/$(ARCH)/lib/lib.a
PLATFORM_LIBS := $(filter-out %/lib.a, $(filter-out -lgcc, $(PLATFORM_LIBS))) $(PLATFORM_LIBGCC)
endif
u-boot-spl-init := $(head-y)
u-boot-spl-main := $(libs-y)
# Linker Script
ifdef CONFIG_SPL_LDSCRIPT
# need to strip off double quotes
LDSCRIPT := $(addprefix $(srctree)/,$(CONFIG_SPL_LDSCRIPT:"%"=%))
endif
ifeq ($(wildcard $(LDSCRIPT)),)
LDSCRIPT := $(srctree)/board/$(BOARDDIR)/u-boot-spl.lds
endif
ifeq ($(wildcard $(LDSCRIPT)),)
LDSCRIPT := $(srctree)/$(CPUDIR)/u-boot-spl.lds
endif
ifeq ($(wildcard $(LDSCRIPT)),)
LDSCRIPT := $(srctree)/arch/$(ARCH)/cpu/u-boot-spl.lds
endif
ifeq ($(wildcard $(LDSCRIPT)),)
$(error could not find linker script)
endif
# Special flags for CPP when processing the linker script.
# Pass the version down so we can handle backwards compatibility
# on the fly.
LDPPFLAGS += \
-include $(srctree)/include/u-boot/u-boot.lds.h \
-include $(objtree)/include/config.h \
-DCPUDIR=$(CPUDIR) \
$(shell $(LD) --version | \
sed -ne 's/GNU ld version \([0-9][0-9]*\)\.\([0-9][0-9]*\).*/-DLD_MAJOR=\1 -DLD_MINOR=\2/p')
quiet_cmd_mkimage = MKIMAGE $@
cmd_mkimage = $(objtree)/tools/mkimage $(MKIMAGEFLAGS_$(@F)) -d $< $@ \
$(if $(KBUILD_VERBOSE:1=), >/dev/null)
MKIMAGEFLAGS_MLO = -T omapimage -a $(CONFIG_SPL_TEXT_BASE)
MKIMAGEFLAGS_MLO.byteswap = -T omapimage -n byteswap -a $(CONFIG_SPL_TEXT_BASE)
MLO MLO.byteswap: $(obj)/u-boot-spl.bin
$(call if_changed,mkimage)
MKIMAGEFLAGS_boot.bin = -T atmelimage
ifeq ($(CONFIG_SPL_GENERATE_ATMEL_PMECC_HEADER),y)
MKIMAGEFLAGS_boot.bin += -n $(shell $(obj)/../tools/atmel_pmecc_params)
boot.bin: $(obj)/../tools/atmel_pmecc_params
endif
boot.bin: $(obj)/u-boot-spl.bin
$(call if_changed,mkimage)
ALL-y += $(obj)/$(SPL_BIN).bin $(obj)/$(SPL_BIN).cfg
ALL-$(CONFIG_OF_SEPARATE) += $(obj)/$(SPL_BIN)-pad.bin $(obj)/$(SPL_BIN)-dtb.bin
ifdef CONFIG_SAMSUNG
ALL-y += $(obj)/$(BOARD)-spl.bin
endif
ifdef CONFIG_SUNXI
ALL-y += $(obj)/sunxi-spl.bin
endif
ifeq ($(CONFIG_SYS_SOC),"at91")
ALL-y += boot.bin
endif
all: $(ALL-y)
quiet_cmd_cat = CAT $@
cmd_cat = cat $(filter-out $(PHONY), $^) > $@
$(obj)/$(SPL_BIN)-dtb.bin: $(obj)/$(SPL_BIN).bin $(obj)/$(SPL_BIN)-pad.bin \
$(obj)/$(SPL_BIN).dtb FORCE
$(call if_changed,cat)
# Create a file that pads from the end of u-boot-spl.bin to bss_end
$(obj)/$(SPL_BIN)-pad.bin: $(obj)/$(SPL_BIN)
@bss_size_str=$(shell $(NM) $< | awk 'BEGIN {size = 0} /__bss_size/ {size = $$1} END {print "ibase=16; " toupper(size)}' | bc); \
dd if=/dev/zero of=$@ bs=1 count=$${bss_size_str} 2>/dev/null;
# Pass the original device tree file through fdtgrep twice. The first pass
# removes any unwanted nodes (i.e. those which don't have the
# 'u-boot,dm-pre-reloc' property and thus are not needed by SPL. The second
# pass removes various unused properties from the remaining nodes.
# The output is typically a much smaller device tree file.
quiet_cmd_fdtgrep = FDTGREP $@
cmd_fdtgrep = $(objtree)/tools/fdtgrep -b u-boot,dm-pre-reloc -RT $< \
-n /chosen -O dtb | \
$(objtree)/tools/fdtgrep -r -O dtb - -o $@ \
$(addprefix -P ,$(subst $\",,$(CONFIG_OF_SPL_REMOVE_PROPS)))
$(obj)/$(SPL_BIN).dtb: dts/dt.dtb
$(call cmd,fdtgrep)
quiet_cmd_cpp_cfg = CFG $@
cmd_cpp_cfg = $(CPP) -Wp,-MD,$(depfile) $(cpp_flags) $(LDPPFLAGS) -ansi \
-DDO_DEPS_ONLY -D__ASSEMBLY__ -x assembler-with-cpp -P -dM -E -o $@ $<
$(obj)/$(SPL_BIN).cfg: include/config.h
$(call if_changed,cpp_cfg)
ifdef CONFIG_SAMSUNG
ifdef CONFIG_VAR_SIZE_SPL
VAR_SIZE_PARAM = --vs
else
VAR_SIZE_PARAM =
endif
$(obj)/$(BOARD)-spl.bin: $(obj)/u-boot-spl.bin
$(if $(wildcard $(objtree)/spl/board/samsung/$(BOARD)/tools/mk$(BOARD)spl),\
$(objtree)/spl/board/samsung/$(BOARD)/tools/mk$(BOARD)spl,\
$(objtree)/tools/mkexynosspl) $(VAR_SIZE_PARAM) $< $@
endif
quiet_cmd_objcopy = OBJCOPY $@
cmd_objcopy = $(OBJCOPY) $(OBJCOPYFLAGS) $(OBJCOPYFLAGS_$(@F)) $< $@
OBJCOPYFLAGS_$(SPL_BIN).bin = $(SPL_OBJCFLAGS) -O binary
$(obj)/$(SPL_BIN).bin: $(obj)/$(SPL_BIN) FORCE
$(call if_changed,objcopy)
LDFLAGS_$(SPL_BIN) += -T u-boot-spl.lds $(LDFLAGS_FINAL)
ifneq ($(CONFIG_SPL_TEXT_BASE),)
LDFLAGS_$(SPL_BIN) += -Ttext $(CONFIG_SPL_TEXT_BASE)
endif
ifdef CONFIG_SUNXI
quiet_cmd_mksunxiboot = MKSUNXI $@
cmd_mksunxiboot = $(objtree)/tools/mksunxiboot $< $@
$(obj)/sunxi-spl.bin: $(obj)/$(SPL_BIN).bin
$(call if_changed,mksunxiboot)
endif
quiet_cmd_u-boot-spl = LD $@
cmd_u-boot-spl = (cd $(obj) && $(LD) $(LDFLAGS) $(LDFLAGS_$(@F)) \
$(patsubst $(obj)/%,%,$(u-boot-spl-init)) --start-group \
$(patsubst $(obj)/%,%,$(u-boot-spl-main)) --end-group \
$(PLATFORM_LIBS) -Map $(SPL_BIN).map -o $(SPL_BIN))
$(obj)/$(SPL_BIN): $(u-boot-spl-init) $(u-boot-spl-main) $(obj)/u-boot-spl.lds FORCE
$(call if_changed,u-boot-spl)
$(sort $(u-boot-spl-init) $(u-boot-spl-main)): $(u-boot-spl-dirs) ;
PHONY += $(u-boot-spl-dirs)
$(u-boot-spl-dirs):
$(Q)$(MAKE) $(build)=$@
quiet_cmd_cpp_lds = LDS $@
cmd_cpp_lds = $(CPP) -Wp,-MD,$(depfile) $(cpp_flags) $(LDPPFLAGS) -ansi \
-D__ASSEMBLY__ -x assembler-with-cpp -P -o $@ $<
$(obj)/u-boot-spl.lds: $(LDSCRIPT) FORCE
$(call if_changed_dep,cpp_lds)
# read all saved command lines
targets := $(wildcard $(sort $(targets)))
cmd_files := $(wildcard $(obj)/.*.cmd $(foreach f,$(targets),$(dir $(f)).$(notdir $(f)).cmd))
ifneq ($(cmd_files),)
$(cmd_files): ; # Do not try to update included dependency files
include $(cmd_files)
endif
PHONY += FORCE
FORCE:
# Declare the contents of the .PHONY variable as phony. We keep that
# information in a variable so we can use it in if_changed and friends.
.PHONY: $(PHONY)