Actually, a lot of work has been done on this by various people. Here is a library that works on:
- Freescale iMX (older Kobo, pre-2021 Nook Glows)
- Mediatek (Kindle)
- Sunxi (current Kobo, possibly 2021 Nook Glow
https://github.com/NiLuJe/FBInk
Not supported are:
- TI OMAP (Nook Simple Touch)
- Rockchip (older Onyx)
- Qualcomm (current Onyx)