Re: [PATCH v9 2/2] arm64: boot: Support Flat Image Tree

[Simon Glass <sjg@chromium.org>]

Hi Masahiro,

On Wed, Dec 13, 2023 at 5:14 AM Will Deacon <will@kernel.org> wrote:
>
> On Fri, Dec 01, 2023 at 08:54:42PM -0700, Simon Glass wrote:
> > Add a script which produces a Flat Image Tree (FIT), a single file
> > containing the built kernel and associated devicetree files.
> > Compression defaults to gzip which gives a good balance of size and
> > performance.
> >
> > The files compress from about 86MB to 24MB using this approach.
> >
> > The FIT can be used by bootloaders which support it, such as U-Boot
> > and Linuxboot. It permits automatic selection of the correct
> > devicetree, matching the compatible string of the running board with
> > the closest compatible string in the FIT. There is no need for
> > filenames or other workarounds.
> >
> > Add a 'make image.fit' build target for arm64, as well. Use
> > FIT_COMPRESSION to select a different algorithm.
> >
> > The FIT can be examined using 'dumpimage -l'.
> >
> > This features requires pylibfdt (use 'pip install libfdt'). It also
> > requires compression utilities for the algorithm being used. Supported
> > compression options are the same as the Image.xxx files. For now there
> > is no way to change the compression other than by editing the rule for
> > $(obj)/image.fit
> >
> > While FIT supports a ramdisk / initrd, no attempt is made to support
> > this here, since it must be built separately from the Linux build.
> >
> > Signed-off-by: Simon Glass <sjg@chromium.org>
> > ---
> >
> > Changes in v9:
> > - Move the compression control into Makefile.lib
> >
> > Changes in v8:
> > - Drop compatible string in FDT node
> > - Correct sorting of MAINTAINERS to before ARM64 PORT
> > - Turn compress part of the make_fit.py comment in to a sentence
> > - Add two blank lines before parse_args() and setup_fit()
> > - Use 'image.fit: dtbs' instead of BUILD_DTBS var
> > - Use '$(<D)/dts' instead of '$(dir $<)dts'
> > - Add 'mkimage' details Documentation/process/changes.rst
> > - Allow changing the compression used
> > - Tweak cover letter since there is only one clean-up patch
> >
> > Changes in v7:
> > - Add Image as a dependency of image.fit
> > - Drop kbuild tag
> > - Add dependency on dtbs
> > - Drop unnecessary path separator for dtbs
> > - Rebase to -next
> >
> > Changes in v5:
> > - Drop patch previously applied
> > - Correct compression rule which was broken in v4
> >
> > Changes in v4:
> > - Use single quotes for UIMAGE_NAME
> >
> > Changes in v3:
> > - Drop temporary file image.itk
> > - Drop patch 'Use double quotes for image name'
> > - Drop double quotes in use of UIMAGE_NAME
> > - Drop unnecessary CONFIG_EFI_ZBOOT condition for help
> > - Avoid hard-coding "arm64" for the DT architecture
> >
> > Changes in v2:
> > - Drop patch previously applied
> > - Add .gitignore file
> > - Move fit rule to Makefile.lib using an intermediate file
> > - Drop dependency on CONFIG_EFI_ZBOOT
> > - Pick up .dtb files separately from the kernel
> > - Correct pylint too-many-args warning for write_kernel()
> > - Include the kernel image in the file count
> > - Add a pointer to the FIT spec and mention of its wide industry usage
> > - Mention the kernel version in the FIT description
> >
> >  Documentation/process/changes.rst |   9 +
> >  MAINTAINERS                       |   7 +
> >  arch/arm64/Makefile               |   7 +-
> >  arch/arm64/boot/.gitignore        |   1 +
> >  arch/arm64/boot/Makefile          |   6 +-
> >  scripts/Makefile.lib              |  16 ++
> >  scripts/make_fit.py               | 291 ++++++++++++++++++++++++++++++
> >  7 files changed, 334 insertions(+), 3 deletions(-)
> >  create mode 100755 scripts/make_fit.py
>
> I'll need Masahiro's Ack on the scripts/ changes before I can take this
> one.

Any thoughts on this request, please?

Regards,
Simon