Quick question about mouse scroll wheel and xorg.conf fie

Marius Gedminas marius at pov.lt
Wed Oct 13 21:58:39 UTC 2010

On Wed, Oct 13, 2010 at 03:01:17PM -0500, Anthony Papillion wrote:
> > That is very strange.  Is it a USB mouse?  Do you see any output if you
> > run xev in a terminal, move the mouse cursor over the xev window, and
> > scroll the wheel?  You should see ButtonPress and ButtonRelease events
> > for buttons 4 and 5.
> Yes, it's a USB mouse that's about a year old. In xev I see the expected
> ButtonPress and ButtonRelease events ONLY when I click the wheel.
> Scrolling produces no output at all. The event is totally ignored.

Hmm.  Could you install evtest and see if it notices scroll wheel
events?  You will need to know the /dev/input/eventX node for your

> Interesting that I see something similar.  Here is the relevent part of
> the Xorg.0.log file. Looks good, right?
> II) config/udev: Adding input device Logitech Optical USB Mouse
> (/dev/input/event6)

(here it is)

> (**) Logitech Optical USB Mouse: Applying InputClass "evdev pointer
> catchall"
> (**) Logitech Optical USB Mouse: always reports core events
> (**) Logitech Optical USB Mouse: Device: "/dev/input/event6"
> (II) Logitech Optical USB Mouse: Found 3 mouse buttons
> (II) Logitech Optical USB Mouse: Found scroll wheel(s)
> (II) Logitech Optical USB Mouse: Found relative axes
> (II) Logitech Optical USB Mouse: Found x and y relative axes
> (II) Logitech Optical USB Mouse: Configuring as mouse
> (**) Logitech Optical USB Mouse: YAxisMapping: buttons 4 and 5

Everything seems to be in order.

> (**) Logitech Optical USB Mouse: EmulateWheelButton: 4,
> EmulateWheelInertia: 10, EmulateWheelTimeout: 200
> (II) XINPUT: Adding extended input device "Logitech Optical USB
> Mouse" (type: MOUSE)
> (II) Logitech Optical USB Mouse: initialized for relative axes.
> (II) config/udev: Adding input device Logitech Optical USB Mouse
> (/dev/input/mouse1)
> (II) No input driver/identifier specified (ignoring)
> I'm not sure if the last line belongs to the mouse detection or not.

Yes.  The kernel exports two different input devices:

  /dev/input/eventX (speaking the evdev protocol)
  /dev/input/mouseY (speaking the PS/2 protocol)

X needs only one of them, so it ignores the other.  (If it didn't
ignore, all mouse events would be duplicated, which wouldn't be fun --
double-clicks every time you make a single click etc.)

> So it seems that my mouse wheel is being detected just not responding.
> I've tried this on another (Windows) computer and the mouse is
> functioning properly so I know my scroll actually does work.
> Odd huh? Any ideas?

Which Ubuntu version is this?  Do you use GNOME or KDE that may have a
setting somewhere to disable the mouse wheel?  Any weird configuration
with xmodmap/xinput?  Do you have any other mice you could test?
Built-in touchpads with a scroll area?  Can you boot a live CD and see
if the mouse wheel works there?

(Basically I'm out of ideas.)

Marius Gedminas
Remember, drive defensively! And of course, the best defense is a good offense!
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