Things I've tried:
wm size 800x480 - seems to change the size of the output within the little square, but doesn't make the square any bigger
wm density (various values) - changes the dpi as expected, but again does nothing about the size of what's actually displayed
changes to build.prop - I don't really know what I'm doing here, but the changes I've made basically seem to have the same effect as the wm command
I'm guessing I need to do something more fundamental than this to get it to work. I should probably point out that there's nothing wrong with the screen itself. I tried it with a raspberry pi and as long as the pi is configured correctly (in its config.txt file) it works fine. I've tried to find an equivalent of that file for android, but all I get is references to running android on a pi.
Presumably, when you're building a rom you need to account for the screen that's going to be connected to the board somehow, however it's actually connected. Can anyone tell me what that procedure is? If I can get it to work without rebuilding the rom, great, but I'm happy to get my hands a bit dirty if necessary, I just need an idea of where to start. I haven't gone any further than flashing a few custom roms so far, so I'm still a bit green, but I'm a software developer and a linux user and nothing about the internals of android looks too tricky, as long as I can see where to start from.
Thanks for any help.