Logitech TrackMan Marble FX scroll wheel patch for the Linux kernel
NOTE I now have a standalone driver available here which is easier to install: https://github.com/xkr47/marblefx
This patch alters the usbmouse kernel driver to support a "scroll wheel mode" using the fourth button (the red button) when connected through a "ID 04d9:1400 Holtek Semiconductor, Inc. PS/2 keyboard + mouse controller" usb-to-ps2 adapter. No idea how things work with other adapters.
It seems the fourth button generates events, but the state of the button is not represented in any bits (at least by said usb-to-ps2 adapter).