Re: [RFC PATCH 6/7] arm64: dts: google: lga: Add lga.its FIT image script

[Simon Glass]

Hi Doug,

On 2026-10-20T15:35:18, Douglas Anderson <dianders@xxxxxxxxxxxx> wrote:
> arm64: dts: google: lga: Add lga.its FIT image script
>
> Add an Image Tree Source (`lga.its`) describing the FIT image for Google
> Tensor G5 (LGA) Pixel 10 family boards (`lga-blazer.dtb`,
> `lga-frankel.dtb`, and `lga-mustang.dtb`) with board and SoC ID/revision
> metadata in the configuration descriptions, allowing the LGA FIT image
> to be built with:
>
>   make \
>     FIT_ITS=google/lga.its \
>     FIT_FACTOR_DTBS=1 \
>     FDTFACTOR_ARGS="--strip-local-fixups --single-base-dtb" \
>     image.fit
>
> NOTE: At the moment, Pixel 10 doesn't directly boot from a FIT
> image. However, packaging scripts will be able to take an image as
> built above and convert it into a format that the bootloader can
> handle.
>
> It should also be noted that the "description" of the various
> [...]
>
>  arch/arm64/boot/dts/google/lga.its | 68 ++++++++++++++++++++++++++++++++++++++
>  1 file changed, 68 insertions(+)

> diff --git a/arch/arm64/boot/dts/google/lga.its b/arch/arm64/boot/dts/google/lga.its
> @@ -0,0 +1,68 @@
> +		fdt-1 {
> +			description = "lga-blazer.dtb";
> +			data = /incbin/("arch/arm64/boot/dts/google/lga-blazer.dtb");
> +			type = "flat_dt";
> +			arch = "arm64";
> +			compression = "none";
> +			hash-1 {
> +				algo = "sha1";
> +			};
> +		};

Just to check, does fdtfactor recalculate hash-1 when it rewrites the
fdt-N data? With FIT_FACTOR_DTBS=1 (as used in the commit message),
mkimage computes the sha1 over the full lga-blazer.dtb and then the
data is replaced by the base or overlay. If the hash is not updated,
anything that verifies it will reject the image. I'm also not sure why
the FDTs get a hash but kernel-1 does not. If the hashes are only
there because the trogdor script has them, it might be simpler to drop
them here, since the packaging scripts repack everything anyway.

> diff --git a/arch/arm64/boot/dts/google/lga.its b/arch/arm64/boot/dts/google/lga.its
> @@ -0,0 +1,68 @@
> +		conf-1 {
> +			description = "Blazer (board_id=0x070406,board_rev=0x010000,soc_id=0x0005,soc_rev=0x010000)";

Since tools are expected to parse this string, please can you add a
comment at the top of the file describing the format? For example: are
the keys required or optional, can they come in any order, are the
numbers always hex, and does the width matter (6 digits for board_id
but 4 for soc_id)? Otherwise the format is whatever the first
packaging script happens to accept, and anyone adding a board or
revision has to copy the existing lines and hope. But I think we
should get this into the FIT spec - will mention that on the cover
letter.

Regards,
Simon