win_info_t
#define DS_GET_FIRST_WINDOW _IOR ('d', 19, win_info_t)
#define DS_GET_NEXT_WINDOW _IOWR('d', 20, win_info_t)
#define DS_GET_MEM_PAGE _IOWR('d', 21, win_info_t)
win_info_t win_info;