I found what causes this. To make the keyboard work on some later Macbook Pros, the usbkbm code now explicitly sets the protocol to the keyboard "boot protocol".
Apparently, this confuses the combined keyboard/trackpad controller in my MacBook, and makes it switch to some strange mode for the mouse part. I removed the call in usbkbm.c, and now both the keyboard and internal mouse work fine. I can't positively say that this is the cause of the problem for all older MacBooks. The one in the bugreport was apparently in "raw mode". Mine didn't seem to have that problem. It did not send 64-byte messages, but 8-byte messages (as advertised). But the messages were screwed up. It'd be good to find a way to initialize all these Macbook controllers so that they report the right trackpad data. - Frank
