[kernel/image_kernel] add "whole rootfs in initrd in kernel image" feature

This patch add the "whole rootfs in initrd in kernel image" feature to
the kernel. The whole root file system in form of an cpio image should
be linked into the kernel.

The procedure is split into two parts:
If the feature is active, during the kernel's compile stage an empty
file is linked into the kernel. Because:
a) the kernel should be compiled in the compile stage
b) the root file system isn't read yet, because it is usually not
   compiled. Maybe we even want to put modules into the rootfs.

The second part happens during the "images" stage. First the cpio is
created, then it is linked into the kernel image. Last but not least the
kernel image is installed to "images/kernel" as usual.

Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

1 files changed, 10 insertions, 0 deletions

diff --git a/platforms/image_kernel.in b/platforms/image_kernel.in
index 0ac048957..e2fee8ca7 100644
--- a/platforms/image_kernel.in
+++ b/platforms/image_kernel.in
@@ -9,6 +9,16 @@ menuconfig IMAGE_KERNEL
 
 if IMAGE_KERNEL
 
+comment "'rootfs in kernel image' is incompatible with 'install kernel into /boot'"
+	depends on KERNEL_INSTALL
+
+config IMAGE_KERNEL_INITRAMFS
+	bool
+	select IMAGE_CPIO
+	depends on !KERNEL_INSTALL
+	select IMAGE_KERNEL_INSTALL_LATE
+	prompt "include root filesystem as initramfs in kernel image"
+
 config IMAGE_KERNEL_INSTALL_EARLY
 	bool
 	default !IMAGE_KERNEL_INSTALL_LATE