Having to use the -K option to mkimage to populate U-Boot's .dtb with the public key while signing the kernel FIT image is often a little awkward. In particular, when using a meta-build system such as bitbake/Yocto, having the tasks of the kernel and U-Boot recipes intertwined, modifying deployed artifacts and rebuilding U-Boot with an updated .dtb is quite cumbersome. Also, in some scenarios one may wish to build U-Boot complete with the public key(s) embedded in the .dtb without the corresponding private keys being present on the same build host.
So this adds a simple tool that allows one to disentangle the kernel and U-Boot builds, by simply copy-pasting just enough of the mkimage code to allow one to add a public key to a .dtb. When using mkimage, some of the information is taken from the .its used to build the kernel (algorithm and key name), so that of course needs to be supplied on the command line.
Signed-off-by: Roman Kopytin Roman.Kopytin@kaspersky.com Cc: Rasmus Villemoes rasmus.villemoes@prevas.dk