On Mon, Jul 06, 2026 at 05:06:42PM +0200, Carlo Caione wrote: > Platforms following EBBR / Arm SystemReady IR keep the devicetree on > a firmware-owned partition, updated independently of the operating > system, rather than shipping it in the OS image or on the EFI System > Partition. U-Boot has no generic way to source the devicetree from such > a partition, so vendors carry out-of-tree machinery for it. > > Add a bootstd helper, firmware_fdt_load(), that assembles the OS > devicetree from a FIT manifest carried on that partition: the FIT images > hold the base DTB and its overlays, and each FIT configuration names one > bootable combination through its 'fdt' property. > > The partition is described in the control devicetree: the bootstd node > carries a 'firmware-fdt-source' phandle to a source node, a child of > the media device owning the partition, which identifies it by GPT type > UUID and/or name. The 'boot_dtb' environment variable may pin an A/B > partition number. > > The error semantics are fail closed: -ENOENT strictly means "no source > configured" (the only case where callers may fall back to their normal > devicetree); once a source is configured, any assembly failure is > fatal, and downstream -ENOENT codes (missing manifest, missing FIT > configuration) are remapped so a missing or bad firmware devicetree is > never silently replaced by an unverified one. Manifest images carrying > a 'load' property are rejected so a misbuilt manifest cannot overwrite > arbitrary memory. > > Signed-off-by: Carlo Caione <[email protected]> > --- > MAINTAINERS | 3 + > boot/Kconfig | 23 ++ > boot/Makefile | 1 + > boot/firmware_fdt.c | 382 > ++++++++++++++++++++++++++++++ > doc/develop/bootstd/firmware_fdt.rst | 94 ++++++++ > doc/develop/bootstd/index.rst | 1 + > doc/device-tree-bindings/firmware-fdt.txt | 149 ++++++++++++
I think I wasn't clear enough on the RFC, sorry. We need to get this binding approved over in https://github.com/devicetree-org/dt-schema/ and I strongly suspect that barebox would be able to make use of this too, so a u-boot prefix would be inappropriate. -- Tom
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