xinput for mouse button mapping

[steve%prd.co.uk@localhost (Steve Blinkhorn)]

I recently replaced my aged and now failed Logitech trackball with an
Elecom HUGE, but I need to remap the buttons to suit certain hand
problems.  All the advice I see says to use xev to see which button
I'm pressing and xinput to change the mapping.  But most of the
buttons don't show up in xev, and xinput says "X Input extension not
available"  Where does one get it and what's it called?

I'm sure I once used a tool that reported raw button numbers, but have
forgotten its name - but it probably began with x - not much of a clue
is it?

-- 
Steve Blinkhorn <steve%prd.co.uk@localhost>