[0/2] allow control DTB to double as "FIT image"

[Rasmus Villemoes]

Hi Simon,

On Fri, May 15 2026, Simon Glass <sjg at chromium.org> wrote:

> Hi Rasmus,
>
> On 2026-05-12T16:16:29, Rasmus Villemoes <ravi at prevas.dk> wrote:
>
>> RFC: allow the control DTB to act as a FIT image
>
> Thanks for the write-up. Makes sense to me.

Thanks, and thanks for the nice review.

> A couple of series-level concerns beyond the per-patch comments.
>
> First, this needs documentation. The control DTB doubling as a FIT
> image, and 'source ${fdtcontroladdr}:foo' becoming a supported idiom,
> deserves a short page under doc/usage/ covering how to set up
> CONFIG_DEVICE_TREE_INCLUDES with an 'images' node, the constraints
> (script type, compression none, etc.) and the security argument from
> the cover letter.

Completely agreed. I'll add a section below "External .dtsi fragments"
in control.rst.

>> I am of course happy to put this exemption for gd->fdt_blob under a
>> CONFIG_ knob if that is deemed necessary.
>
> Please decide this now rather than leaving it open. My preference is a
> Kconfig option (default n) so boards keep the strict
> fit_check_format() behaviour unless they opt in. That also gives a
> natural home for the doc/usage/ page and makes it discoverable via
> menuconfig. What do you think?

I've added a CONFIG_CONTROL_DTB_AS_FIT option (as always, naming is the
hardest part), with a short help text and a pointer to control.rst for
further details.

I'll respond to the per-patch comments and then send v2 shortly.

Rasmus