XSetDeviceMode man page
XSetDeviceMode — change the mode of a device
XSetDeviceMode( Display *display,
Specifies the connection to the X server.
Specifies the device whose mode is to be changed.
Specifies the mode.You can pass Absolute,or Relative.
The XSetDeviceMode request changes the mode of an input device
that is capable of reporting either absolute positional
information or relative motion information. Not all input
devices are capable of reporting motion data, and not all are
capable of changing modes from Absolute to Relative.
XSetDeviceMode can generate a BadDevice or BadMode error.
An invalid device was specified. The specified device
does not exist or has not been opened by this client via
XOpenInputDevice. This error may also occur if some
other client has caused the specified device to become
the X keyboard or X pointer device via the
XChangeKeyboardDevice or XChangePointerDevice requests.
This error may occur if an XSetDeviceMode request is
made specifying a device that has no valuators and
reports no axes of motion.
An invalid mode was specified. This error will also be
returned if the specified device is not capable of
supporting the XSetDeviceMode request.