[Buildroot] [PATCH 4/9 v2] fs/initramfs: cleanup and enhance comments

[Romain Naour <romain.naour@gmail.com>]

Hi Yann, All,

Le 11/03/2016 19:41, Yann E. MORIN a ?crit :
> rootfs-initramfs is not using the generic fs infrastructure, because
> there is virtually nothing to do to build the initramfs image: there is
> no actual image to be built to begin with.
> 
> The only purpose of rootfs-initramfs is to ensure the rootfs.cpio image
> is built and then that the Linux kernel is rebuilt with that rootfs.cpio
> as initramfs source.
> 
> Using variables of the fs infra like if it were used is misleading. It
> looked nice as long as there was the possibility that rootfs-initramfs
> would one day use the fs infra. But there's no way that will happen any
> time soon.
> 
> Furthermore, the linux' rule linux-rebuild-with-initramfs now already
> depends on rootfs-cpio by itself, so we need not duplicate this
> dependency in rootfs-initramfs.
> LINUX_DIR
> Still, we want to advertise that the dependency is on rootfs-cpio, so
> we get nice dependency graphs (and not expose the internal
> linux-rebuild-with-initramfs rule to the users).
> 
> So, remove the variables and directly define the rules.
> 
> Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
> Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
> ---
>  fs/initramfs/initramfs.mk | 22 +++++++++++++++-------
>  1 file changed, 15 insertions(+), 7 deletions(-)
> 
> diff --git a/fs/initramfs/initramfs.mk b/fs/initramfs/initramfs.mk
> index db50812..9aca9c8 100644
> --- a/fs/initramfs/initramfs.mk
> +++ b/fs/initramfs/initramfs.mk
> @@ -5,17 +5,25 @@
>  #
>  ################################################################################
>  
> -ROOTFS_INITRAMFS_DEPENDENCIES += rootfs-cpio
> -
> -ROOTFS_INITRAMFS_POST_TARGETS += linux-rebuild-with-initramfs
> -
> -
>  # The generic fs infrastructure isn't very useful here.
> +#
> +# The initramfs image does not actually build an image; its only purpose is:
> +# 1- to ensure rootfs.cpio is generated,
> +# 2- to then rebuild the kernel with rootfs.cpio as initramfs
> +#
> +# Note: ordering of the dependencies is not guaranteed here, but in
> +# linux/linux.mk, via the .stamp_initramfs_rebuilt stamp file, which depends
> +# on the rootfs-cpio filesystem rule.

As said previously, there is no more .stamp_initramfs_rebuilt file.

Otherwise
Reviewed-by: Romain Naour <romain.naour@gmail.com>

Best regards,
Romain

> +#
> +# Note: the trick here is that we directly depend on rebuilding the Linux
> +# kernel image (which itself depends on the rootfs-cpio rule), while we
> +# advertise that our dependency is on the rootfs-cpio rule, which is
> +# cleaner in the dependency graph.
>  
> -rootfs-initramfs: $(ROOTFS_INITRAMFS_DEPENDENCIES) $(ROOTFS_INITRAMFS_POST_TARGETS)
> +rootfs-initramfs: linux-rebuild-with-initramfs
>  
>  rootfs-initramfs-show-depends:
> -	@echo $(ROOTFS_INITRAMFS_DEPENDENCIES)
> +	@echo rootfs-cpio
>  
>  .PHONY: rootfs-initramfs rootfs-initramfs-show-depends
>  
>