XSetDeviceMode - Man Page

#include <X11/extensions/XInput.h>

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.