Progress on palmtop version
The display is now working; it turns out the frame buffer access isn't so clear-cut as on a PC, in that the display needs to be told when you've just updated a rectangle, it's a simple enough modification, though.
Initially, I thought I'd (have to) replace the existing interface with ROLF, but now I think I'll try to have them running simultaneously on separate virtual terminals. This means the server will have to configure and react to VT change signals (rather than the simplistic approach of waiting to be sent another keypress when changed to another VT). Then, I just need a simple program on each one to perform a chvt to the other.
The touchscreen delivers events through an input event device (see Documentation/input/input.txt in the Linux kernel); this is a much nicer interface than the /dev/psaux one I was using and handles keyboards as well, so I'm moving over to that for all platforms. I need to calibrate the touchscreen, though, the reported return values from the device cover a larger area than are actually returned, so with my initial code, the cursor wouldn't move out of a smaller rectangle in the middle of the screen.
To get anything working at all, I've installed dropbear (a ssh server), so that I can login remotely via the network. Executable files don't work from the memory cards, so I'm installing to a directory under the root.