NR_LDISCS
if (disc < N_TTY || disc >= NR_LDISCS)
return (*pos < NR_LDISCS) ? pos : NULL;
return (*pos < NR_LDISCS) ? pos : NULL;
static struct tty_ldisc_ops *tty_ldiscs[NR_LDISCS];
if (new_ldisc->num < N_TTY || new_ldisc->num >= NR_LDISCS)