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ref-manual/ref-classes: update kernel-fitimage with Initramfs bundle and boot script

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This commit adds the description of the Initramfs bundle and boot script
new features implemented in the kernel-fitimage class.

Change-Id: Ifffa6b850308aa7ceadc4f117806cffad0137137
(From yocto-docs rev: a55c16555366c0adbf4a087b86574b07972cbc52)

Signed-off-by: Abdellatif El Khlifi <abdellatif.elkhlifi@arm.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
This commit is contained in:
Abdellatif El Khlifi
2021-01-19 10:54:47 +00:00
committed by Richard Purdie
parent e6a0be545d
commit d8698dc755
1 changed files with 27 additions and 5 deletions
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32
documentation/ref-manual/classes.rst
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@@ -1375,11 +1375,13 @@ generation.
===========================
The ``kernel-fitimage`` class provides support to pack a kernel image,
device trees and a RAM disk into a single FIT image. In theory, a FIT
image can support any number of kernels, RAM disks and device trees.
device trees, a U-boot script, a Initramfs bundle and a RAM disk
into a single FIT image. In theory, a FIT image can support any number
of kernels, U-boot scripts, Initramfs bundles, RAM disks and device-trees.
However, ``kernel-fitimage`` currently only supports
limited usescases: just one kernel image, an optional RAM disk, and
any number of device trees.
limited usescases: just one kernel image, an optional U-boot script,
an optional Initramfs bundle, an optional RAM disk, and any number of
device tree.
To create a FIT image, it is required that :term:`KERNEL_CLASSES`
is set to include "kernel-fitimage" and :term:`KERNEL_IMAGETYPE`
@@ -1406,7 +1408,27 @@ Only a single RAM disk can be added to the FIT image created by
The address where the RAM disk image is to be loaded by U-Boot
is specified by :term:`UBOOT_RD_LOADADDRESS` and the entrypoint by
:term:`UBOOT_RD_ENTRYPOINT`. The ramdisk is added to FIT image when
:term:`INITRAMFS_IMAGE` is specified.
:term:`INITRAMFS_IMAGE` is specified and that :term:`INITRAMFS_IMAGE_BUNDLE`
is set to 0.
Only a single Initramfs bundle can be added to the FIT image created by
``kernel-fitimage`` and the Initramfs bundle in FIT is optional.
In case of Initramfs, the kernel is configured to be bundled with the rootfs
in the same binary (example: zImage-initramfs-:term:`MACHINE`.bin).
When the kernel is copied to RAM and executed, it unpacks the Initramfs rootfs.
The Initramfs bundle can be enabled when :term:`INITRAMFS_IMAGE`
is specified and that :term:`INITRAMFS_IMAGE_BUNDLE` is set to 1.
The address where the Initramfs bundle is to be loaded by U-boot is specified
by :term:`UBOOT_LOADADDRESS` and the entrypoint by :term:`UBOOT_ENTRYPOINT`.
Only a single U-boot boot script can be added to the FIT image created by
``kernel-fitimage`` and the boot script is optional.
The boot script is specified in the ITS file as a text file containing
U-boot commands. When using a boot script the user should configure the
U-boot ``do_install`` task to copy the script to sysroot.
So the script can be included in the the FIT image by the ``kernel-fitimage``
class. At run-time, U-boot CONFIG_BOOTCOMMAND define can be configured to
load the boot script from the FIT image and executes it.
The FIT image generated by ``kernel-fitimage`` class is signed when the
variables :term:`UBOOT_SIGN_ENABLE`, :term:`UBOOT_MKIMAGE_DTCOPTS`,