ATMIOC_SPECIAL
#define ATM_SETSC _IOW('a',ATMIOC_SPECIAL+1,int)
#define ATM_SETBACKEND _IOW('a',ATMIOC_SPECIAL+2,atm_backend_t)
#define ATM_NEWBACKENDIF _IOW('a',ATMIOC_SPECIAL+3,atm_backend_t)