XSetDeviceMode man page
XSetDeviceMode — change the mode of a device
XSetDeviceMode( Display *display, XDevice *device, int mode);
display Specifies the connection to the X server.
device Specifies the device whose mode is to be changed.
mode 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.
BadDevice 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.
BadMatch This error may occur if an XSetDeviceMode request is made specifying a device that has no valuators and reports no axes of motion.
BadMode An invalid mode was specified. This error will also be returned if the specified device is not capable of supporting the XSetDeviceMode request.