2016-09-01 4:09 GMT+09:00 Robert P. J. Day rpjday@crashcourse.ca:

really a Kbuild question, i realize, but i'm looking at common/Makefile, and i'm having trouble understanding the flipping back and forth, as in:

obj-$(CONFIG_ENV_IS_IN_DATAFLASH) += env_dataflash.o obj-$(CONFIG_ENV_IS_IN_EEPROM) += env_eeprom.o extra-$(CONFIG_ENV_IS_EMBEDDED) += env_embedded.o obj-$(CONFIG_ENV_IS_IN_EEPROM) += env_embedded.o extra-$(CONFIG_ENV_IS_IN_FLASH) += env_embedded.o obj-$(CONFIG_ENV_IS_IN_NVRAM) += env_embedded.o

what is the rationale for the jumping between "obj-" and "extra-"? thanks.

rday

linux/Documentation/kbuild/makefiles.txt says as follows:

--- 6.6 Building non-kbuild targets

extra-y

extra-y specifies additional targets created in the current directory, in addition to any targets specified by obj-*.

Listing all targets in extra-y is required for two purposes: 1) Enable kbuild to check changes in command lines - When $(call if_changed,xxx) is used 2) kbuild knows what files to delete during "make clean"

Example: #arch/x86/kernel/Makefile extra-y := head.o init_task.o

In this example, extra-y is used to list object files that shall be built, but shall not be linked as part of built-in.o.