Makefile

#
# kbuild file for usr/ - including initramfs image
#

klibcdirs:;
PHONY += klibcdirs

# Find out "preferred" ramdisk compressor. Order of preference is
#  1. bzip2 efficient, and likely to be present
#  2. gzip former default
#  3. lzma
#  4. none

# None of the above
suffix_y                   =

# Lzma, but no gzip nor bzip2
suffix_$(CONFIG_RD_LZMA)   = .lzma

# Gzip, but no bzip2
suffix_$(CONFIG_RD_GZIP)   = .gz

# Bzip2
suffix_$(CONFIG_RD_BZIP2)  = .bz2


# Generate builtin.o based on initramfs_data.o
obj-$(CONFIG_BLK_DEV_INITRD) := initramfs_data$(suffix_y).o

# initramfs_data.o contains the compressed initramfs_data.cpio image.
# The image is included using .incbin, a dependency which is not
# tracked automatically.
$(obj)/initramfs_data$(suffix_y).o: $(obj)/initramfs_data.cpio$(suffix_y) FORCE

#####
# Generate the initramfs cpio archive

hostprogs-y := gen_init_cpio
initramfs   := $(CONFIG_SHELL) $(srctree)/scripts/gen_initramfs_list.sh
ramfs-input := $(if $(filter-out "",$(CONFIG_INITRAMFS_SOURCE)), \
			$(shell echo $(CONFIG_INITRAMFS_SOURCE)),-d)
ramfs-args  := \
        $(if $(CONFIG_INITRAMFS_ROOT_UID), -u $(CONFIG_INITRAMFS_ROOT_UID)) \
        $(if $(CONFIG_INITRAMFS_ROOT_GID), -g $(CONFIG_INITRAMFS_ROOT_GID))

# .initramfs_data.cpio.d is used to identify all files included
# in initramfs and to detect if any files are added/removed.
# Removed files are identified by directory timestamp being updated
# The dependency list is generated by gen_initramfs.sh -l
ifneq ($(wildcard $(obj)/.initramfs_data.cpio.d),)
	include $(obj)/.initramfs_data.cpio.d
endif

quiet_cmd_initfs = GEN     $@
      cmd_initfs = $(initramfs) -o $@ $(ramfs-args) $(ramfs-input)

targets := initramfs_data.cpio.gz initramfs_data.cpio.bz2 initramfs_data.cpio.lzma initramfs_data.cpio
# do not try to update files included in initramfs
$(deps_initramfs): ;

$(deps_initramfs): klibcdirs
# We rebuild initramfs_data.cpio if:
# 1) Any included file is newer then initramfs_data.cpio
# 2) There are changes in which files are included (added or deleted)
# 3) If gen_init_cpio are newer than initramfs_data.cpio
# 4) arguments to gen_initramfs.sh changes
$(obj)/initramfs_data.cpio$(suffix_y): $(obj)/gen_init_cpio $(deps_initramfs) klibcdirs
	$(Q)$(initramfs) -l $(ramfs-input) > $(obj)/.initramfs_data.cpio.d
	$(call if_changed,initfs)