thank you for your answer. I was thinking about how to update the internal firmware without the original LEGO-Software. The EV3-firmware-Vx.bin is the complete 16 MB flash which seems to be flashed during the update process. I made a script taking the bin-file apart in the mtd-parts so I would be able to update the sections separately. The uBoot-part never changed so that one does not even need any update.
Do you have any schematics? Is it like TI eXperimentier Kit?
I tried to use the original kernel with the leJOS distribution but that one only produced funny pixel on the display while booting...
This has nothing tot do with leJOS, I know. leJOS even does not fit into the internal flash. It is just the idea of being able to update without LEGO software and without Windows.
Oh, and now I have a clue how to realize the update idea. I have to setup a sdcard similar to the one of leJOS which reads and writes at the times when the system allows to use the mtd devices... So thank you very much for your hint
[some time later...] Heureka - it works
Thank you very much for your hint again