Symbol: MOUSE_PS2INTELLI_BUTTON4DOWN
sys/dev/atkbdc/psm.c
5018
ms.button |= (c & MOUSE_PS2INTELLI_BUTTON4DOWN) ?
usr.sbin/moused/msconvd/msconvd.c
1658
act->button |= (pBuf[0] & MOUSE_PS2INTELLI_BUTTON4DOWN)