[PATCH] kbuild: add target to build a cpio containing modules

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

From: Sascha Hauer <s.hauer@pengutronix.de>

Add a new package target to build a cpio archive containing the kernel
modules. This is particularly useful to supplement an existing initramfs
with the kernel modules so that the root filesystem can be started with
all needed kernel modules without modifying it.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Co-developed-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
---
 .gitignore               |  5 +++++
 Makefile                 |  2 +-
 scripts/Makefile.package | 17 +++++++++++++++++
 3 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/.gitignore b/.gitignore
index 86a1ba0d90353962183b47c0c657ec877e5b2f9f..764d115400d90f0904b8f60ea8851a7860c16411 100644
--- a/.gitignore
+++ b/.gitignore
@@ -96,6 +96,11 @@ modules.order
 #
 /tar-install/
 
+#
+# modules directory (make cpio-modules-pkg)
+#
+/modules-install/
+
 #
 # pacman files (make pacman-pkg)
 #
diff --git a/Makefile b/Makefile
index fb4389aa5d5f1776f7bb5988102ed54f92491de7..19c7900d02ed5eee06f00820c138591b42e895e1 100644
--- a/Makefile
+++ b/Makefile
@@ -1583,7 +1583,7 @@ CLEAN_FILES += vmlinux.symvers modules-only.symvers \
 # Directories & files removed with 'make mrproper'
 MRPROPER_FILES += include/config include/generated          \
 		  arch/$(SRCARCH)/include/generated .objdiff \
-		  debian snap tar-install PKGBUILD pacman \
+		  debian snap tar-install modules-install PKGBUILD pacman \
 		  .config .config.old .version \
 		  Module.symvers \
 		  certs/signing_key.pem \
diff --git a/scripts/Makefile.package b/scripts/Makefile.package
index 74bcb9e7f7a4516473481468a0fcf700c3bead33..20eec9e2dec4dda3fa0ef64a15b80dccdcb55f90 100644
--- a/scripts/Makefile.package
+++ b/scripts/Makefile.package
@@ -189,6 +189,22 @@ tar-pkg: linux-$(KERNELRELEASE)-$(ARCH).tar
 tar%-pkg: linux-$(KERNELRELEASE)-$(ARCH).tar.% FORCE
 	@:
 
+modules-install: FORCE
+	$(Q)$(MAKE) -f $(srctree)/Makefile
+	$(Q)rm -rf $@
+	$(Q)$(MAKE) -f $(srctree)/Makefile INSTALL_MOD_PATH=$@ modules_install
+
+quiet_cmd_cpio = CPIO    $@
+      cmd_cpio = $(srctree)/usr/gen_initramfs.sh $< > $@
+
+modules-$(KERNELRELEASE)-$(ARCH).cpio: modules-install
+	$(Q)$(MAKE) -f $(srctree)/Makefile $(build)=usr cpio-data= usr/gen_init_cpio
+	$(call cmd,cpio)
+
+PHONY += cpio-modules-pkg
+cpio-modules-pkg: modules-$(KERNELRELEASE)-$(ARCH).cpio
+	@:
+
 # perf-tar*-src-pkg - generate a source tarball with perf source
 # ---------------------------------------------------------------------------
 
@@ -245,6 +261,7 @@ help:
 	@echo '  tarbz2-pkg          - Build the kernel as a bzip2 compressed tarball'
 	@echo '  tarxz-pkg           - Build the kernel as a xz compressed tarball'
 	@echo '  tarzst-pkg          - Build the kernel as a zstd compressed tarball'
+	@echo '  cpio-modules-pkg    - Build the kernel modules as cpio archive'
 	@echo '  perf-tar-src-pkg    - Build the perf source tarball with no compression'
 	@echo '  perf-targz-src-pkg  - Build the perf source tarball with gzip compression'
 	@echo '  perf-tarbz2-src-pkg - Build the perf source tarball with bz2 compression'

---
base-commit: e9a6fb0bcdd7609be6969112f3fbfcce3b1d4a7c
change-id: 20251115-cpio-modules-pkg-70d85a69892b

Best regards,
-- 
Ahmad Fatoum <a.fatoum@pengutronix.de>