qmk_firmware/keyboards/handwired/trackpoint/keymaps/default/keymap.c

#include "trackpoint.h"

const uint16_t PROGMEM keymaps[][MATRIX_ROWS][MATRIX_COLS] = {
    [0] = KEYMAP(
        KC_BTN1,    KC_BTN3,    KC_BTN2 \
    )
};