I have not done anything with the raspberry pi for a while as I cannot really see a usable system being attainable for quite a while yet as the rpi still needs some infrastructure that will improve performance.
I have all sorts of thoughts but don't really know if any are useful or if others would want to work on them, unfortunatly I am too busy and too disorganised to get much done, and only just realised that Michael Haberler had sent me an email months ago with git repo details to upload my work.
I think my current driver works in most circumstances, but it is not totally deterministic and it is possible for the dma buffers to get out of sync with the real time servo loop in some circumstances, although I partially implemented flagging of when the dma was running out steps, i have not implemented anything to automatically increase the number of steps written by the servo loop stepgen.
My main aim is to get a decent gui cnc system working on the rpi, I know linuxcnc runs okay headless but I would like the cheap gui working if its possible.
As the axis system works very poorly on the rpi I am waiting for other things to happen, maybe wayland/weston and gtk/glade on weston will be implemented, or maybe a fast cross platform python gles system will be created. There are also load of other considerations that maybe need to be addressed with the kernel and locking dma, and interupts and other stuff, and the RT_PREEMPT patches are apparently quite a hack job still.
I was considering rewriting a gui in python with gles widgets avoiding a need to gtk or other dependencies that can slow things down, but think maybe that is too much work. Also I was thinking about some sort of direct control and path creation from a 3d model rather than gcode, using opengl clipping planes to calculate tool paths and access. All stuff way beyond what I have time to do and probably also beyond skill level, so I was just wasting time.
Anyways as regards licences of my code all the stuff I have published is GPL unless otherwise stated. And if/when I get around to writting a full hal rpi dma io driver I will release it as GPL, but I doubt I will get around to doing much more anytime soon until other parts of the system are working better or unless someone pays me to do it.
Sorry if other people are waiting for a decent linuxcnc system on the rpi, but I think there is not much point my hacking on it anymore until other parts of the system are working better, I may have another look at things once xwayland is working on the rpi.