taglinefilesource code
OPOST1659drivers/char/tty_io.ctp->c_oflag = OPOST | ONLCR;
OPOST1665drivers/char/tty_io.ctp->c_oflag = OPOST | ONLCR | XTABS;
OPOST1670drivers/char/tty_io.ctp->c_oflag = OPOST | ONLCR;
OPOST186include/linux/tty.h#define O_POST(tty)  _O_FLAG((tty),OPOST)