On Wed, May 13, 2026 at 06:13:14AM +0200, Heinrich Schuchardt wrote: > Am 13. Mai 2026 04:09:29 MESZ schrieb Daniel Golle <[email protected]>: > >Add documentation for CONFIG_FIT_VERITY which allows U-Boot to > >construct dm-mod.create= and dm-mod.waitfor= kernel command-line > >parameters from dm-verity metadata embedded in FIT filesystem > >sub-images. > > > > [...] > > > >+Prerequisites > >+------------- > >+ > >+* **Linux uImage.FIT block driver** – the kernel must include the FIT block > >+ driver that exposes loadable sub-images as ``/dev/fit0``, ``/dev/fit1``, > > > The dtb file format of FIT images only guarantees 4 byte alignment. Does that > match with the requirement of file-system drivers including dma access if the > FIT is for example on eMMC? Or do we need a mechanism to enforce higher > alignment in FIT images?
The fitblk driver requires the 'filesystem' image to start and end on block boundaries of the underlying block device. As the 'filesystem' image is outside of the FIT structure itself (external data) this can be achieved by having `mkimage -E -B 0x1000`. This is a restriction of the current implementation of the fitblk driver to avoid the complexity (and computation overhead) which comes with unaligned access (a lot of memcpy, basically...). Future implementations may no longer have that restriction, while of course performance will always slightly suffer from the image not being aligned with the block size of the lower device. Hence I consider this current resitriction something to be documented along with the fitblk driver, and outside of the scope of what U-Boot itself is involved with.
