ts_setup() will try to find, open and configure the touch screen device. On success it allocates memory
for a new touch screen device, opens and links the input event device to it and loads and initialises all
modules configured in the tslib configuration file TSLIB_CONFFILE.
If dev_name is NULLts_setup() will use the device defined by the TSLIB_TSDEVICE environment variable.
If TSLIB_TSDEVICE is not defined ts_setup() will try to use following devices:
/dev/input/ts,
/dev/input/touchscreen,
/dev/touchscreen/ucb1x00.
After that we ts_setup() scans /dev/input/event* for the first device with property INPUT_PROP_DIRECT.