axfs and SPI XiP boot

[swdevlimacon]

Hi!

I'm going to have a go at adding AXFS and XiP boot to this great script.

Possibly using this as a guide - "Shrinking the kernel with a hammer"
https://lwn.net/Articles/748198/

Follow my changes here. I may add a PR later. :-)
https://github.com/limaconaudio/yarvt

[mickflemm]

Thanks ! Give me some time to push some changes I have on my queue that enable per-target kernel configuration files ;-)

[mickflemm]

I don't have a target yet with an SPI NOR flash or a storage device capable of XiP (directly addressable). We are already doing XiP due to initramfs which is xz compressed so storage-wise it takes the same space. I guess AXFS would make sense for some target that boots from a fast directly-addressable device (e.g. NVDIMM) but over SPI it would be much slower from just copying the initramfs image on memory and running it from there. We 'll gain some more memory space because AXFS will decompress "on-demand" but still I don't know if it's worth it. Anyway, have fun with it and let me know how it goes ;-)