[RFC PATCH 0/5] partition parser for U-Boot's uImage.FIT

From: Daniel Golle
Date: Mon Apr 25 2022 - 10:57:36 EST

Add uImage.FIT partition parser and wire it up to allow mounting
filesystem sub-images from uImage.FIT in GPT partitions as well as
mtdblock and ubiblock devices within Linux (e.g. as root filesystem).

Using uImage.FIT to store the root filesystem besides kernel and dtb has
several obvious advantages which are hard to obtain in any other way:
* single image accross different storage types
* dynamically sized partitions for kernel and rootfs
* hash also for rootfs checked by U-Boot before launching kernel
* images may include additional filesystems e.g. for localization or

For this to work, the image has to be created with external data and
sub-images aligned to the system's memory page boundaries, ie.
mkimage -E -B 0x1000 -p 0x1000 ...

Booting such images has been supported by U-Boot since v2018.01.

A previous version of this partition parser is in production use on
some OpenWrt devices, eg. the BananaPi R64 where using the FIT parser
allows booting the very same image from eMMC, SD Card or SPI-NAND/UBI
and also using it as a firmware-upgrade image at the same time.

Most recently U-Boot now also passes down the selected configuration
node name via device tree to allow the partition parser (or userspace
process via sysfs) to identify the image configuration.

Device Tree schema for that:

Daniel Golle (5):
block: add new flag to add partitions read-only
block: add partition parser for U-Boot uImage.FIT
partitions/efi: add support for uImage.FIT sub-partitions
mtd_blkdevs: scan partitions on mtdblock if FIT_PARTITION is set
mtd/ubi/block: scan for partitions in case FIT_PARTITION is set

block/blk.h | 1 +
block/partitions/Kconfig | 14 ++
block/partitions/Makefile | 1 +
block/partitions/check.h | 5 +
block/partitions/core.c | 6 +
block/partitions/efi.c | 9 +
block/partitions/efi.h | 3 +
block/partitions/fit.c | 352 ++++++++++++++++++++++++++++++++++++++
drivers/mtd/mtd_blkdevs.c | 2 +
drivers/mtd/ubi/block.c | 2 +
11 files changed, 401 insertions(+)
create mode 100644 block/partitions/fit.c