Re: [PATCH v2 2/2] kbuild: add target to build a cpio containing modules

[Nicolas Schier <nsc@kernel.org>]

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On Tue, Nov 25, 2025 at 02:18:20PM +0100, Ahmad Fatoum wrote:
> 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>
> Reviewed-by: Simon Glass <sjg@chromium.org>
> Tested-by: Simon Glass <sjg@chromium.org>
> Co-developed-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
> Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
> ---
>  scripts/Makefile.package | 20 ++++++++++++++++++++
>  1 file changed, 20 insertions(+)
> 
> diff --git a/scripts/Makefile.package b/scripts/Makefile.package
> index 74bcb9e7f7a4516473481468a0fcf700c3bead33..83bfcf7cb09fd2d69b97e0c19a2b99c728835e8d 100644
> --- a/scripts/Makefile.package
> +++ b/scripts/Makefile.package
> @@ -189,6 +189,25 @@ tar-pkg: linux-$(KERNELRELEASE)-$(ARCH).tar
>  tar%-pkg: linux-$(KERNELRELEASE)-$(ARCH).tar.% FORCE
>  	@:
>  
> +# modules-cpio-pkg - generate an initramfs with the modules
> +# ---------------------------------------------------------------------------
> +
> +.tmp_modules_cpio: FORCE
> +	$(Q)$(MAKE) -f $(srctree)/Makefile
> +	$(Q)rm -rf $@
> +	$(Q)$(MAKE) -f $(srctree)/Makefile INSTALL_MOD_PATH=$@ modules_install

Do you know why '-f $(srctree)/Makefile' is necessary here?  As this
and the make call two lines above call common top-level targets, I do
not see the reason for explicitly adding the Makefile path.  Am I
missing something; or have you observed problems without '-f'?

> +
> +quiet_cmd_cpio = CPIO    $@
> +      cmd_cpio = $(CONFIG_SHELL) $(srctree)/usr/gen_initramfs.sh -o $@ $<
> +
> +modules-$(KERNELRELEASE)-$(ARCH).cpio: .tmp_modules_cpio
> +	$(Q)$(MAKE) $(build)=usr usr/gen_init_cpio
> +	$(call cmd,cpio)

Removing the '$(MAKE) $(build)=usr usr/gen_init_cpio' line and adding


PHONY += usr_gen_init_cpio
usr_gen_init_cpio: scripts_basic
	$(Q)$(MAKE) $(build)=usr usr/gen_init_cpio

modules-cpio-pkg: usr_gen_init_cpio


to top-level Makefile could be used to allow make to compile
gen_init_cpio in parallel instead of sequential.  And it simplifies a
possible move of gen_init_cpio from usr/ to scripts/, as Nathan
suggested.

What do you think?  (Top-level Makefile addition should probably better
be integrated into patch 1.)  I can also send this as a follow-up patch
after merging your patches.


Nevertheless,
Tested-by: Nicolas Schier <nsc@kernel.org>

If there are no further remarks, I am going to merge the patch set
before the weekend.

Thanks and kind regards,
Nicolas

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