Lennart Augustsson <lennart@augustsson.net>  wrote:
 > An alternative would be to use similar code as for merging keyboard
 > events to merge mouse events.  We could then have a special virtual
 > mouse device which the real mouse send their events to.  This virtual
 > mouse should also be accessible from userland to inject events into,
 > that way we could have a /dev/mouse that would work for all mice.
 > Serial mice would inject their events into it via moused, a userland
 > program (which we can borrow from FreeBSD).
 > A locator on the wsmouse device would tell the mouse where to
 > send its events.
 > 

As an aside, this would allow us to build a thing like SGI's "nds" 
(Network Dual-head Software) which basically sets up a 1 pixel-wide
window on the edge of a remote display and on the edge of the local
display.  When the mouse enters that window on the local display, it
gets unmapped and mapped on the remote display; mouse and keyboard
events are sent through the network and injected into the keyboard
and mouse event queue on the remote... Effectively creating a multi-
head display across a number of machines.

I use this at work where I have an old SS2 running NetBSD and an
SGI machine both sharing the same keyboard/mouse... (the Sun one).