Comment 2 for bug 317025

I did an experiment that makes me believe that this is more of an unsupported feature than an actual bug.
I took the A4tech mouse, that is a PS/2 mouse, and plugged it into a PS/2 to USB converter, and ran that through a KVM. This means that Ubuntu has no idea that this is the same mouse tested before.
All other USB mice converted horizontal scrolling to 7 times faster vertical scrolling. This mouse, no matter how it is hooked up, converts horizontal scrolling to 2 times faster vertical scrolling.
So this proves to me that the mouse driver is not converting the horizontal scrolling into vertical scrolling, but the mouse itself.
So, either there needs to be a command sent to the mouse to change its behavior, or the driver is not interpreting the data from the horizontal scrolling correctly.
When I looked at the USB data under windows, vertical scrolling was either a +1 or -1 in the scroll data. I never saw anything else there. I'm guessing that in the default mode, USB mice are reporting +7 or -7 in this same byte for horizontal scrolling. In the mode that Windows activates, it appears that the mouse sends all zeros (via an interrupt transaction) which is an indication to the driver that it needs to ask the mouse (via a bulk transfer) to see what actually happened.

Could someone please point me at the source code for whatever part of Linux handles the mouse? I'd like to have a look at it.