rk3588编译-uboot交叉编译-scripts/Kbuild.include分析

if_changed函数

http://t.zoukankan.com/idyllcheung-p-11591962.html

# Execute command if command has changed or prerequisite(s) are updated.
#
if_changed = $(if $(strip $(any-prereq) $(arg-check)),                       \
    @set -e;                                                             \
    $(echo-cmd) $(cmd_$(1));                                             \
    printf '%s\n' 'cmd_$@ := $(make-cmd)' > $(dot-target).cmd)

• any-prereq变量
  作用：存储比目标还要新的依赖文件与不存在的依赖文件
  any-prereq = $(filter-out $(PHONY),$?) $(filter-out $(PHONY) $(wildcard $^),$^)
  $(filter-out $(PHONY),$?)：将 $? 中的所有伪目标去掉，不然可能会将 FORCE 这种目标也带进来，如果此时返回非空，那么说明有比目标还要新的依赖文件。
  $(filter-out $(PHONY) $(wildcard $^),$^)：$(wildcard $^) 匹配当前目录下的所有依赖文件(已经存在的)，然后再使用 $(filter-out $(PHONY) $(wildcard $^),$^) 将伪目标以及当前目录下匹配的文件列表从整个 $^ 列表中删除，如果返回不为空，那么说明某些依赖文件不存在，也就是说这些不存在的依赖文件还没生成 -- 这是因为某些依赖文件需要在编译时才会生成。

• arg-check变量

  ifneq ($(KBUILD_NOCMDDEP),1)
  # Check if both arguments has same arguments. Result is empty string if equal.
  # User may override this check using make KBUILD_NOCMDDEP=1
  arg-check = $(strip $(filter-out $(cmd_$(1)), $(cmd_$@)) \
                  $(filter-out $(cmd_$@),   $(cmd_$(1))) )
  else
  arg-check = $(if $(strip $(cmd_$@)),,1)
  endif

打印结果KBUILD_NOCMDDEP为空，所以上面的脚本走的if分支。

arg-check = $(strip $(filter-out $(cmd_$(1)), $(cmd_$@)) \
                    $(filter-out $(cmd_$@),   $(cmd_$(1))) )

以uboot为例：

u-boot: $(u-boot-init) $(u-boot-main) u-boot.lds FORCE
    +$(call if_changed,u-boot__)

传入的参数$(1)就是u-boot__，$@就是u-boot。然后arg-check会对cmd_u-boot__与cmd_u-boot变量进行处理。

u-boot-init

u-boot-init := $(head-y)
head-y是定义在include arch/$(ARCH)/Makefile中，head-y := arch/arm/cpu/$(CPU)/start.o

u-boot-main

u-boot-main := $(libs-y)

libs-y: arch/arm/cpu/built-in.o arch/arm/cpu/armv8/built-in.o arch/arm/lib/built-in.o arch/arm/mach-rockchip/built-in.o board/rockchip/evb_rk3588/built-in.o cmd/built-in.o common/built-in.o disk/built-in.o drivers/built-in.o drivers/cpu/built-in.o drivers/dma/built-in.o drivers/gpio/built-in.o drivers/i2c/built-in.o drivers/mtd/built-in.o drivers/mtd/onenand/built-in.o drivers/mtd/spi/built-in.o drivers/net/built-in.o drivers/net/phy/built-in.o drivers/pci/built-in.o drivers/power/built-in.o drivers/power/battery/built-in.o drivers/power/charge/built-in.o drivers/power/domain/built-in.o drivers/power/dvfs/built-in.o drivers/power/fuel_gauge/built-in.o drivers/power/io-domain/built-in.o drivers/power/mfd/built-in.o drivers/power/pmic/built-in.o drivers/power/regulator/built-in.o drivers/serial/built-in.o drivers/spi/built-in.o drivers/usb/cdns3/built-in.o drivers/usb/common/built-in.o drivers/usb/dwc3/built-in.o drivers/usb/emul/built-in.o drivers/usb/eth/built-in.o drivers/usb/gadget/built-in.o drivers/usb/gadget/udc/built-in.o drivers/usb/host/built-in.o drivers/usb/musb-new/built-in.o drivers/usb/musb/built-in.o drivers/usb/phy/built-in.o drivers/usb/ulpi/built-in.o env/built-in.o fs/built-in.o lib/built-in.o net/built-in.o test/built-in.o test/dm/built-in.o

arg-check变量的值：/home/xinyi/android/code/Task1-debian/rk3588_source/prebuilts/gcc/linux-x86/aarch64/gcc-arm-10.3-2021.07-x86_64-aarch64-none-linux-gnu/bin/aarch64-none-linux-gnu-ld.bfd -pie --gc-sections -Bstatic --no-dynamic-linker -Ttext 0x00200000 -o u-boot -T u-boot.lds arch/arm/cpu/armv8/start.o --start-group arch/arm/cpu/built-in.o arch/arm/cpu/armv8/built-in.o arch/arm/lib/built-in.o arch/arm/mach-rockchip/built-in.o board/rockchip/evb_rk3588/built-in.o cmd/built-in.o common/built-in.o disk/built-in.o drivers/built-in.o drivers/cpu/built-in.o drivers/dma/built-in.o drivers/gpio/built-in.o drivers/i2c/built-in.o drivers/mtd/built-in.o drivers/mtd/onenand/built-in.o drivers/mtd/spi/built-in.o drivers/net/built-in.o drivers/net/phy/built-in.o drivers/pci/built-in.o drivers/power/built-in.o drivers/power/battery/built-in.o drivers/power/charge/built-in.o drivers/power/domain/built-in.o drivers/power/dvfs/built-in.o drivers/power/fuel_gauge/built-in.o drivers/power/io-domain/built-in.o drivers/power/mfd/built-in.o drivers/power/pmic/built-in.o drivers/power/regulator/built-in.o drivers/serial/built-in.o drivers/spi/built-in.o drivers/usb/cdns3/built-in.o drivers/usb/common/built-in.o drivers/usb/dwc3/built-in.o drivers/usb/emul/built-in.o drivers/usb/eth/built-in.o drivers/usb/gadget/built-in.o drivers/usb/gadget/udc/built-in.o drivers/usb/host/built-in.o drivers/usb/musb-new/built-in.o drivers/usb/musb/built-in.o drivers/usb/phy/built-in.o drivers/usb/ulpi/built-in.o env/built-in.o fs/built-in.o lib/built-in.o net/built-in.o test/built-in.o test/dm/built-in.o --end-group -L /home/xinyi/android/code/Task1-debian/rk3588_source/prebuilts/gcc/linux-x86/aarch64/gcc-arm-10.3-2021.07-x86_64-aarch64-none-linux-gnu/bin/../lib/gcc/aarch64-none-linux-gnu/10.3.1 -lgcc -Map u-boot.map; true

any-prereq变量的值：arch/arm/cpu/armv8/start.o arch/arm/cpu/built-in.o arch/arm/cpu/armv8/built-in.o arch/arm/lib/built-in.o arch/arm/mach-rockchip/built-in.o board/rockchip/evb_rk3588/built-in.o cmd/built-in.o common/built-in.o disk/built-in.o drivers/built-in.o drivers/cpu/built-in.o drivers/dma/built-in.o drivers/gpio/built-in.o drivers/i2c/built-in.o drivers/mtd/built-in.o drivers/mtd/onenand/built-in.o drivers/mtd/spi/built-in.o drivers/net/built-in.o drivers/net/phy/built-in.o drivers/pci/built-in.o drivers/power/built-in.o drivers/power/battery/built-in.o drivers/power/charge/built-in.o drivers/power/domain/built-in.o drivers/power/dvfs/built-in.o drivers/power/fuel_gauge/built-in.o drivers/power/io-domain/built-in.o drivers/power/mfd/built-in.o drivers/power/pmic/built-in.o drivers/power/regulator/built-in.o drivers/serial/built-in.o drivers/spi/built-in.o drivers/usb/cdns3/built-in.o drivers/usb/common/built-in.o drivers/usb/dwc3/built-in.o drivers/usb/emul/built-in.o drivers/usb/eth/built-in.o drivers/usb/gadget/built-in.o drivers/usb/gadget/udc/built-in.o drivers/usb/host/built-in.o drivers/usb/musb-new/built-in.o drivers/usb/musb/built-in.o drivers/usb/phy/built-in.o drivers/usb/ulpi/built-in.o env/built-in.o fs/built-in.o lib/built-in.o net/built-in.o test/built-in.o test/dm/built-in.o u-boot.lds