xinput: Do I want xorg.conf? Do I want hal? Do I want udev?

[Tom Horsley]

I currently have my new fedora 12 system with no xorg.conf
and a script that runs when I login to execute xinput commands
to setup my trackball for draglock.

This scheme falls apart when I switch my KVM switch to
another system. The mouse is "unplugged" and the xinput
settings are lost.

The information (if you can call it that) on how I might
correct this is both spotty and contradictory. The whole
universe seems to have decided that xorg.conf files
are the spawn of the devil, so I shouldn't use one of
those to fix it (and indeed, the xorg.conf man page seems
to indicate that I must use the evdev device number, which
I have no way of predicting, to select the device).

I find a lot of notes in various places saying what I really
need is a hal .fdi policy file, but determining what to put
in such a file is more problematic. And, of course, just like
xorg.conf, such a policy file would be a system wide setting,
not a per-user setting for mouse behavior which should clearly
be a user preference. Then there is the fact that I can also
find mailing list entries that say hal is oh so 20th century
and is on the way out to be replaced by something better (where
"better" apparently means "even fewer people understand it" :-).

Is udev the thing to use instead of hal? If so, that is
another system wide setting and another cryptic file
I don't know how to write :-).

I see that I get dbus system messages when I plug or unplug a
mouse or keyboard. Is the grand plan to have a per user daemon
listening for these and re-applying xinput settings when they
show up? Does this daemon exist already and I just don't know
its name? Do we really need yet another daemon? How long before
linux runs out of PIDs? :-).

Where does a poor linux user who just wants his trackball to be
useful with one hand go to figure out what he is supposed to
do?