Re: [PATCH v2 10/10] fdtfactor: Add compiled FIT image factoring support

[Simon Glass]

On 2026-10-28T21:46:49, Douglas Anderson <dianders@xxxxxxxxxxxx> wrote:
> fdtfactor: Add compiled FIT image factoring support
>
> Bootloaders such as depthcharge on Chromebooks and U-Boot use Flattened
> Image Tree (FIT) images to bundle a kernel image with multiple board FDT
> blobs (`fdt-1`, `fdt-2`, ...) and per-board configuration nodes.
>
> Add `-F`/`--fit`, `--outfile`, and `--single-base-dtb` options to
> `fdtfactor` to factor a compiled FIT image directly:
>
> - Parse non-overlay `type = "flat_dt"` nodes under `/images`,
>   decompressing their `data` blobs according to their `compression`
>   property (`none`, `lz4`, `lzma`, `xz`, `gzip`).
> - Reject FIT images containing `signature*` subnodes under `/images/*`
>   or `/configurations/*`, as modifying FDT blobs and configurations
>   would invalidate cryptographic signatures.
> - Partition the `flat_dt` blobs into compatible factor groups (by
>   compression, architecture, FDT header fields, and node-path overlap)
>   so a single FIT image containing multiple board/SoC families produces
>   a separate `fdt-base-1`, `fdt-base-2`, etc. for each family.
> - Support `--single-base-dtb` to force all `flat_dt` blobs into a single
>   base DTB regardless of node-path overlap, failing only if their FDT
>   headers, architecture, or compression differ.
> - Insert each `fdt-base-N` node into `/images`, replace each factored
>   `fdt-*` node's `data` with its compressed `.dtbo` overlay, recompute
>   any `hash*` subnode digests, and prepend `fdt-base-N` to each matching
>   configuration's `fdt` string list while preserving all other
>   configuration properties (`description`, `compatible`, etc.,
>   populating `compatible` from the board DTB's root node when omitted)
>   and any pre-existing overlay entries.
>
> Add uncompressed, LZ4-compressed multi-family, signed-FIT rejection, and
> `--single-base-dtb` FIT image test cases to the `fdtfactor` test suite.
>
> Assisted-by: Gemini:gemini-pro-prerelease
> Signed-off-by: Douglas Anderson <dianders@xxxxxxxxxxxx>
>
>  README.md                  |  17 ++
>  fdtfactor                  | 588 ++++++++++++++++++++++++++++++++++++++++++---
>  tests/Makefile.tests       |   2 +-
>  tests/fdtfactor_lz4.its    | 109 +++++++++
>  tests/fdtfactor_other1.dts |  33 +++
>  tests/fdtfactor_other2.dts |  33 +++
>  tests/fdtfactor_test.its   | 109 +++++++++
>  tests/run_tests.sh         | 158 +++++++++++-
>  8 files changed, 1018 insertions(+), 31 deletions(-)

Reviewed-by: Simon Glass <sjg@xxxxxxxxxxxx>

BTW, 'FIT image' actually means an image in a FIT, so I think you
should try to call the whole thing a 'FIT' instead.