update-uboot is a completely self-contained way to update u-boot. The generated binary includes the updated u-boot binary and Linux kernel module to allow rw access to the (often protected) /dev/mtd0 partition.
git clone https://git.sr.ht/~monadnock/zig-mtd
This code only currently supports mipsel out of the box. The only parts specific to mipsel are:
mtd-rw.ko; The embedded kernel module is compiled for mipsel. You can replace this file with a version compiled for your arch, or comment out the function if you don't require it.
uboot-feb2019.bin: Same story. This is the version of u-boot I needed for mt7628 product. You'll almost certainly want to replace this file. Ask your doctor what version of u-boot is right for you
The ioctl numbers used to ERASE and UNLOCK the mtd are arch specific
zig couldn't grok the nested ioctl #define horrors from the mtd headers. The easiest way I've found to determine these magic numbers is to compile the mtd-magic.c file in the repo with your target toolchain and run it on the target. It'll print out the macro expansions (e.g.
mipsel-openwrt-linux-gcc -o mtd-magic mtd-magic.c)