When I set up Red Hat Linux on my Sony Viao PCG-FX140 laptop... at
first I was only able to use an external (Microsoft) USB mouse on the
machine. That's because I didn't know how to specify the laptop's
touchpad as an input-device in Red Hat. Also, I didn't know how to
specify that =either= a USB mouse =or= the trackpad should work
(simultaneously).

To save =you= the trouble, here's how!

In the directory "/etc/X11" there's an important file called
"XF86Config." (Note that this filename, like all Unix/Linux
filenames, is case-sensitive.) This file (see "man XF86Config") is
composed of "sections." There are "inputdevice" sections for, well,
input-devices, and other sections for your screen, keyboard, and
so-on. Needless to say, make a backup =first.=

You'll need to be "root," of course.

(What, do you ask, is "X11?" It's a package called XWindows, which
has nothing to do .. thankfully .. with =that= operating-system. It's
the system that actually makes your computer work in graphic mode.
It's what runs your display, or displays, and recognizes the input
from whatever you have attached to your computer. It blows away
everything "that other operating-system" ever thought of doing, but
that should come as no surprise to Linux folks, eh?)

First, I used "redhat-configure-mouse" to set up the trackpad, which
is properly known as a "GlidePoint PS/2." This creates the following
section:

Section "InputDevice"
Identifier "Mouse0"
Driver "Mouse"
Option "Protocol" "GlidePointPS/2"
Option "Device" "/dev/psaux"
Option "ZAxisMapping" "4 5"
Option "Emulate3Buttons" "Yes"
EndSection

Now for the magic! I want an external USB mouse to work also, and for
it to work simultaneously with the trackpad. That is, either or both
will move the same mouse-pointer. There are =two= bits to this magic.

First, you un-comment the mouse-section that you'll probably find is
already in the file: (yes, it is -another- "InputDevice" section)

Section "InputDevice"
Identifier "USBMouse"
Driver "Mouse"
Option "Protocol" "IMPS/2"
Option "Device" "/dev/input/mice"
Option "ZAxisMapping" "4 5"
Option "Emulate3Buttons" "no"
EndSection

(note: my mouse has 3 buttons. If yours doesn't, you know what to
do...)

Now for the other part of the magic. Having thus described the device
to XWindows, you must now specify what you want to do with it.

At the top of the file you'll find a "ServerLayout" section. You'll
see that it contains several statements including references to the
devices described in the other sections... identifying each one, of
course, by its "Identifier." Yours may be different, but mine reads:

Section "ServerLayout"
Identifier "Default Layout"
Screen 0 "Screen0" 0 0
InputDevice "Mouse0" "CorePointer"
InputDevice "Keyboard0" "CoreKeyboard"
InputDevice "USBMouse" "SendCoreEvents"
EndSection

The last InputDevice statement, above, is the second bit of magic.
This specifies that the "USBMouse" input-device can "send core events"
just like the "core pointer" device can. This causes XWindows to
recognize either or both devices as "moving the mouse pointer."

You need only add the last InputDevice statement to this section;
leave the other statements that you find there, in your system, alone.

You =did= make that backup copy first, didn't you?

To actually make these changes come into effect, you need to restart
XWindows now. Very likely, pressing "Ctrl+Alt+Backspace" will do
that, logging you off in the process. Otherwise, you can do this by
killing the "X" process, which you must do as Root. Or you can simply
reboot the machine. Your laptop, your choice.

In the extremely unlikely event that you find yourself without a
working GUI display, "Ctrl+Alt+F2" will probably give you a login
prompt, character-mode, where you can log in, rename the XF86Config
files to put your backup-copy back into place, and restart. But if
you're a careful typist, I'm sure you won't have had any problems at
all.

Hope this helps!