[Buildroot] [PATCH 1/1] Add support for custom initramfs contents

[Raphael Jacob <r.jacob2002@gmail.com>]

From: Richard Kunze <richard.kunze@web.de>

Signed-off-by: Raphael Jacob <r.jacob2002@gmail.com>
---
 fs/initramfs/Config.in    | 34 +++++++++++++++++++++++++++++++++-
 fs/initramfs/initramfs.mk | 18 +++++++++++++++++-
 linux/linux.mk            |  8 ++++----
 3 files changed, 54 insertions(+), 6 deletions(-)

diff --git a/fs/initramfs/Config.in b/fs/initramfs/Config.in
index 9d5a3f92e6..9b7ac9475e 100644
--- a/fs/initramfs/Config.in
+++ b/fs/initramfs/Config.in
@@ -1,6 +1,22 @@
 config BR2_TARGET_ROOTFS_INITRAMFS
 	bool "initial RAM filesystem linked into linux kernel"
 	depends on BR2_LINUX_KERNEL
+	help
+	  Integrate an initramfs inside the kernel image.
+	  This integration will take place automatically.
+
+	  The initramfs contents can either be the full root filesystem
+	  generated by buildroot, or an image built from a custom list
+	  of files specified via the BR2_TARGET_ROOTFS_INITRAMFS_CUSTOM_CONTENTS
+	  config option.
+
+choice
+	prompt "initial RAM filesystem contents"
+	depends on BR2_TARGET_ROOTFS_INITRAMFS
+
+config BR2_TARGET_ROOTFS_INITRAMFS_ROOTFS
+	bool "rootfs.cpio"
+	depends on BR2_TARGET_ROOTFS_INITRAMFS
 	select BR2_TARGET_ROOTFS_CPIO
 	help
 	  Integrate the root filesystem generated by Buildroot as an
@@ -13,10 +29,26 @@ config BR2_TARGET_ROOTFS_INITRAMFS
 	  is used, regardless of how buildroot's cpio archive is
 	  configured.
 
-	  Note that enabling initramfs together with another filesystem
+	  Note that enabling this option together with another filesystem
 	  formats doesn't make sense: you would end up having two
 	  identical root filesystems, one embedded inside the kernel
 	  image, and one separately.
+config BR2_TARGET_ROOTFS_INITRAMFS_CUSTOM
+	bool "custom initramfs contents"
+	depends on BR2_TARGET_ROOTFS_INITRAMFS
+	help
+	  Use the contents of BR2_TARGET_ROOTFS_INITRAMFS_CUSTOM_CONTENTS
+	  as the linux kernel configuration variable CONFIG_INITRAMFS_SOURCE
+
+endchoice
+
+config BR2_TARGET_ROOTFS_INITRAMFS_CUSTOM_CONTENTS
+	string "custom initramfs contents"
+	depends on BR2_TARGET_ROOTFS_INITRAMFS_CUSTOM
+	help
+	  Custom value to use as CONFIG_INITRAMFS_SOURCE linux kernel configuration
+	  variable. See Documentation/filesystems/ramfs-rootfs-initramfs.txt in the
+	  linux kernel sources for details.
 
 comment "initramfs needs a Linux kernel to be built"
 	depends on !BR2_LINUX_KERNEL
diff --git a/fs/initramfs/initramfs.mk b/fs/initramfs/initramfs.mk
index c751093214..ef3fdc6d3d 100644
--- a/fs/initramfs/initramfs.mk
+++ b/fs/initramfs/initramfs.mk
@@ -4,6 +4,12 @@
 #
 ################################################################################
 
+ifeq ($(BR2_TARGET_ROOTFS_INITRAMFS_ROOTFS),y)
+ROOTFS_INITRAMFS_DEPENDENCIES += rootfs-cpio
+endif
+
+ROOTFS_INITRAMFS_DEPENDENCIES += $(BINARIES_DIR)/initramfs.cpio
+
 # The generic fs infrastructure isn't very useful here.
 #
 # The initramfs image does not actually build an image; its only purpose is:
@@ -19,13 +25,23 @@
 # advertise that our dependency is on the rootfs-cpio rule, which is
 # cleaner in the dependency graph.
 
-rootfs-initramfs: linux-rebuild-with-initramfs
+rootfs-initramfs: $(ROOTFS_INITRAMFS_DEPENDENCIES) linux-rebuild-with-initramfs
 
 rootfs-initramfs-show-depends:
 	@echo rootfs-cpio
 
 .PHONY: rootfs-initramfs rootfs-initramfs-show-depends
 
+ifeq ($(BR2_TARGET_ROOTFS_INITRAMFS_ROOTFS),y)
+$(BINARIES_DIR)/initramfs.cpio: rootfs-cpio
+	ln -sf rootfs.cpio $(BINARIES_DIR)/initramfs.cpio
+endif
+
+ifeq ($(BR2_TARGET_ROOTFS_INITRAMFS_CUSTOM),y)
+$(BINARIES_DIR)/initramfs.cpio: target-finalize $(call qstrip,$(BR2_TARGET_ROOTFS_INITRAMFS_CUSTOM_CONTENTS))
+	$(LINUX_DIR)/usr/gen_init_cpio $(BR2_TARGET_ROOTFS_INITRAMFS_CUSTOM_CONTENTS) > $(BINARIES_DIR)/initramfs.cpio
+endif
+
 ifeq ($(BR2_TARGET_ROOTFS_INITRAMFS),y)
 TARGETS_ROOTFS += rootfs-initramfs
 endif
diff --git a/linux/linux.mk b/linux/linux.mk
index 7f4c916671..b98043419b 100644
--- a/linux/linux.mk
+++ b/linux/linux.mk
@@ -278,8 +278,8 @@ define LINUX_KCONFIG_FIXUP_CMDS
 	# replaced later by the real cpio archive, and the kernel will be
 	# rebuilt using the linux-rebuild-with-initramfs target.
 	$(if $(BR2_TARGET_ROOTFS_INITRAMFS),
-		touch $(BINARIES_DIR)/rootfs.cpio
-		$(call KCONFIG_SET_OPT,CONFIG_INITRAMFS_SOURCE,"$${BR_BINARIES_DIR}/rootfs.cpio",$(@D)/.config)
+		touch $(BINARIES_DIR)/initramfs.cpio
+		$(call KCONFIG_SET_OPT,CONFIG_INITRAMFS_SOURCE,"$${BR_BINARIES_DIR}/initramfs.cpio",$(@D)/.config)
 		$(call KCONFIG_SET_OPT,CONFIG_INITRAMFS_ROOT_UID,0,$(@D)/.config)
 		$(call KCONFIG_SET_OPT,CONFIG_INITRAMFS_ROOT_GID,0,$(@D)/.config))
 	$(if $(BR2_ROOTFS_DEVICE_CREATION_STATIC),,
@@ -501,11 +501,11 @@ endif # BR_BUILDING
 $(eval $(kconfig-package))
 
 # Support for rebuilding the kernel after the cpio archive has
-# been generated.
+# been generated in $(BINARIES_DIR)/initramfs.cpio.
 .PHONY: linux-rebuild-with-initramfs
 linux-rebuild-with-initramfs: $(LINUX_DIR)/.stamp_target_installed
 linux-rebuild-with-initramfs: $(LINUX_DIR)/.stamp_images_installed
-linux-rebuild-with-initramfs: rootfs-cpio
+linux-rebuild-with-initramfs: $(BINARIES_DIR)/initramfs.cpio
 linux-rebuild-with-initramfs:
 	@$(call MESSAGE,"Rebuilding kernel with initramfs")
 	# Build the kernel.
-- 
2.18.0