[RFC PATCH 00/20] boot: add OpenWrt boot method and on-demand FIT loading

[Marek Vasut]

On 2/16/26 10:21 PM, Daniel Golle wrote:

Hi,

> This RFC series adds a new boot method for OpenWrt's "uImage.FIT with
> embedded rootfs" firmware model, along with the underlying infrastructure
> to load FIT images on-demand directly from storage devices without copying
> them entirely to RAM first.
> 
> I would like to discuss the design with U-Boot maintainers and fellow
> OpenWrt developers before submitting a formal patch series.

[...]

> 4. On-demand loading: None of the existing methods support loading FIT
>     subimages directly from storage. OpenWrt's FIT images typically
>     contain a 5-20 MB squashfs that does NOT need to be copied to RAM —
>     the kernel maps it directly from flash. The bootloader only needs
>     to load the kernel and DTB (~5-10 MB), not the entire 20-50 MB
>     container. This requires a new loading abstraction.

Isn't this partial loading exactly what SPL does when the fitImage is 
generated with external data (mkimage -E) ? SPL loads and traverses the 
tree, and then loads the remaining chunks (files) only when needed if I 
recall it right ?

Can that SPL code be reused instead ?