MOUSE_PS2_YNEG
buf[0] |= MOUSE_PS2_YNEG;
*y = (pb->ipacket[0] & MOUSE_PS2_YNEG) ?
y = (c & MOUSE_PS2_YNEG) ?
((y < 0) ? MOUSE_PS2_YNEG : 0);
if (c & MOUSE_PS2_YNEG)
act->dy = (pBuf[0] & MOUSE_PS2_YNEG) ? -(pBuf[2] - 256) : -pBuf[2];