196fd7ce5SGreg Kroah-Hartman #include <linux/types.h> 296fd7ce5SGreg Kroah-Hartman #include <linux/major.h> 396fd7ce5SGreg Kroah-Hartman #include <linux/errno.h> 496fd7ce5SGreg Kroah-Hartman #include <linux/signal.h> 596fd7ce5SGreg Kroah-Hartman #include <linux/fcntl.h> 696fd7ce5SGreg Kroah-Hartman #include <linux/sched.h> 796fd7ce5SGreg Kroah-Hartman #include <linux/interrupt.h> 896fd7ce5SGreg Kroah-Hartman #include <linux/tty.h> 996fd7ce5SGreg Kroah-Hartman #include <linux/tty_driver.h> 1096fd7ce5SGreg Kroah-Hartman #include <linux/tty_flip.h> 1196fd7ce5SGreg Kroah-Hartman #include <linux/devpts_fs.h> 1296fd7ce5SGreg Kroah-Hartman #include <linux/file.h> 1396fd7ce5SGreg Kroah-Hartman #include <linux/console.h> 1496fd7ce5SGreg Kroah-Hartman #include <linux/timer.h> 1596fd7ce5SGreg Kroah-Hartman #include <linux/ctype.h> 1696fd7ce5SGreg Kroah-Hartman #include <linux/kd.h> 1796fd7ce5SGreg Kroah-Hartman #include <linux/mm.h> 1896fd7ce5SGreg Kroah-Hartman #include <linux/string.h> 1996fd7ce5SGreg Kroah-Hartman #include <linux/slab.h> 2096fd7ce5SGreg Kroah-Hartman #include <linux/poll.h> 2196fd7ce5SGreg Kroah-Hartman #include <linux/proc_fs.h> 2296fd7ce5SGreg Kroah-Hartman #include <linux/init.h> 2396fd7ce5SGreg Kroah-Hartman #include <linux/module.h> 2496fd7ce5SGreg Kroah-Hartman #include <linux/device.h> 2596fd7ce5SGreg Kroah-Hartman #include <linux/wait.h> 2696fd7ce5SGreg Kroah-Hartman #include <linux/bitops.h> 2796fd7ce5SGreg Kroah-Hartman #include <linux/delay.h> 2896fd7ce5SGreg Kroah-Hartman #include <linux/seq_file.h> 2996fd7ce5SGreg Kroah-Hartman 3096fd7ce5SGreg Kroah-Hartman #include <linux/uaccess.h> 3196fd7ce5SGreg Kroah-Hartman #include <asm/system.h> 3296fd7ce5SGreg Kroah-Hartman 3396fd7ce5SGreg Kroah-Hartman #include <linux/kbd_kern.h> 3496fd7ce5SGreg Kroah-Hartman #include <linux/vt_kern.h> 3596fd7ce5SGreg Kroah-Hartman #include <linux/selection.h> 3696fd7ce5SGreg Kroah-Hartman 3796fd7ce5SGreg Kroah-Hartman #include <linux/smp_lock.h> /* For the moment */ 3896fd7ce5SGreg Kroah-Hartman 3996fd7ce5SGreg Kroah-Hartman #include <linux/kmod.h> 4096fd7ce5SGreg Kroah-Hartman #include <linux/nsproxy.h> 4196fd7ce5SGreg Kroah-Hartman 4296fd7ce5SGreg Kroah-Hartman /* 4396fd7ce5SGreg Kroah-Hartman * This guards the refcounted line discipline lists. The lock 4496fd7ce5SGreg Kroah-Hartman * must be taken with irqs off because there are hangup path 4596fd7ce5SGreg Kroah-Hartman * callers who will do ldisc lookups and cannot sleep. 4696fd7ce5SGreg Kroah-Hartman */ 4796fd7ce5SGreg Kroah-Hartman 4896fd7ce5SGreg Kroah-Hartman static DEFINE_SPINLOCK(tty_ldisc_lock); 4996fd7ce5SGreg Kroah-Hartman static DECLARE_WAIT_QUEUE_HEAD(tty_ldisc_wait); 50100eeae2SJiri Slaby static DECLARE_WAIT_QUEUE_HEAD(tty_ldisc_idle); 5196fd7ce5SGreg Kroah-Hartman /* Line disc dispatch table */ 5296fd7ce5SGreg Kroah-Hartman static struct tty_ldisc_ops *tty_ldiscs[NR_LDISCS]; 5396fd7ce5SGreg Kroah-Hartman 5496fd7ce5SGreg Kroah-Hartman static inline struct tty_ldisc *get_ldisc(struct tty_ldisc *ld) 5596fd7ce5SGreg Kroah-Hartman { 5696fd7ce5SGreg Kroah-Hartman if (ld) 5796fd7ce5SGreg Kroah-Hartman atomic_inc(&ld->users); 5896fd7ce5SGreg Kroah-Hartman return ld; 5996fd7ce5SGreg Kroah-Hartman } 6096fd7ce5SGreg Kroah-Hartman 6196fd7ce5SGreg Kroah-Hartman static void put_ldisc(struct tty_ldisc *ld) 6296fd7ce5SGreg Kroah-Hartman { 6396fd7ce5SGreg Kroah-Hartman unsigned long flags; 6496fd7ce5SGreg Kroah-Hartman 6596fd7ce5SGreg Kroah-Hartman if (WARN_ON_ONCE(!ld)) 6696fd7ce5SGreg Kroah-Hartman return; 6796fd7ce5SGreg Kroah-Hartman 6896fd7ce5SGreg Kroah-Hartman /* 6996fd7ce5SGreg Kroah-Hartman * If this is the last user, free the ldisc, and 7096fd7ce5SGreg Kroah-Hartman * release the ldisc ops. 7196fd7ce5SGreg Kroah-Hartman * 7296fd7ce5SGreg Kroah-Hartman * We really want an "atomic_dec_and_lock_irqsave()", 7396fd7ce5SGreg Kroah-Hartman * but we don't have it, so this does it by hand. 7496fd7ce5SGreg Kroah-Hartman */ 7596fd7ce5SGreg Kroah-Hartman local_irq_save(flags); 7696fd7ce5SGreg Kroah-Hartman if (atomic_dec_and_lock(&ld->users, &tty_ldisc_lock)) { 7796fd7ce5SGreg Kroah-Hartman struct tty_ldisc_ops *ldo = ld->ops; 7896fd7ce5SGreg Kroah-Hartman 7996fd7ce5SGreg Kroah-Hartman ldo->refcount--; 8096fd7ce5SGreg Kroah-Hartman module_put(ldo->owner); 8196fd7ce5SGreg Kroah-Hartman spin_unlock_irqrestore(&tty_ldisc_lock, flags); 8296fd7ce5SGreg Kroah-Hartman 8396fd7ce5SGreg Kroah-Hartman kfree(ld); 8496fd7ce5SGreg Kroah-Hartman return; 8596fd7ce5SGreg Kroah-Hartman } 8696fd7ce5SGreg Kroah-Hartman local_irq_restore(flags); 87100eeae2SJiri Slaby wake_up(&tty_ldisc_idle); 8896fd7ce5SGreg Kroah-Hartman } 8996fd7ce5SGreg Kroah-Hartman 9096fd7ce5SGreg Kroah-Hartman /** 9196fd7ce5SGreg Kroah-Hartman * tty_register_ldisc - install a line discipline 9296fd7ce5SGreg Kroah-Hartman * @disc: ldisc number 9396fd7ce5SGreg Kroah-Hartman * @new_ldisc: pointer to the ldisc object 9496fd7ce5SGreg Kroah-Hartman * 9596fd7ce5SGreg Kroah-Hartman * Installs a new line discipline into the kernel. The discipline 9696fd7ce5SGreg Kroah-Hartman * is set up as unreferenced and then made available to the kernel 9796fd7ce5SGreg Kroah-Hartman * from this point onwards. 9896fd7ce5SGreg Kroah-Hartman * 9996fd7ce5SGreg Kroah-Hartman * Locking: 10096fd7ce5SGreg Kroah-Hartman * takes tty_ldisc_lock to guard against ldisc races 10196fd7ce5SGreg Kroah-Hartman */ 10296fd7ce5SGreg Kroah-Hartman 10396fd7ce5SGreg Kroah-Hartman int tty_register_ldisc(int disc, struct tty_ldisc_ops *new_ldisc) 10496fd7ce5SGreg Kroah-Hartman { 10596fd7ce5SGreg Kroah-Hartman unsigned long flags; 10696fd7ce5SGreg Kroah-Hartman int ret = 0; 10796fd7ce5SGreg Kroah-Hartman 10896fd7ce5SGreg Kroah-Hartman if (disc < N_TTY || disc >= NR_LDISCS) 10996fd7ce5SGreg Kroah-Hartman return -EINVAL; 11096fd7ce5SGreg Kroah-Hartman 11196fd7ce5SGreg Kroah-Hartman spin_lock_irqsave(&tty_ldisc_lock, flags); 11296fd7ce5SGreg Kroah-Hartman tty_ldiscs[disc] = new_ldisc; 11396fd7ce5SGreg Kroah-Hartman new_ldisc->num = disc; 11496fd7ce5SGreg Kroah-Hartman new_ldisc->refcount = 0; 11596fd7ce5SGreg Kroah-Hartman spin_unlock_irqrestore(&tty_ldisc_lock, flags); 11696fd7ce5SGreg Kroah-Hartman 11796fd7ce5SGreg Kroah-Hartman return ret; 11896fd7ce5SGreg Kroah-Hartman } 11996fd7ce5SGreg Kroah-Hartman EXPORT_SYMBOL(tty_register_ldisc); 12096fd7ce5SGreg Kroah-Hartman 12196fd7ce5SGreg Kroah-Hartman /** 12296fd7ce5SGreg Kroah-Hartman * tty_unregister_ldisc - unload a line discipline 12396fd7ce5SGreg Kroah-Hartman * @disc: ldisc number 12496fd7ce5SGreg Kroah-Hartman * @new_ldisc: pointer to the ldisc object 12596fd7ce5SGreg Kroah-Hartman * 12696fd7ce5SGreg Kroah-Hartman * Remove a line discipline from the kernel providing it is not 12796fd7ce5SGreg Kroah-Hartman * currently in use. 12896fd7ce5SGreg Kroah-Hartman * 12996fd7ce5SGreg Kroah-Hartman * Locking: 13096fd7ce5SGreg Kroah-Hartman * takes tty_ldisc_lock to guard against ldisc races 13196fd7ce5SGreg Kroah-Hartman */ 13296fd7ce5SGreg Kroah-Hartman 13396fd7ce5SGreg Kroah-Hartman int tty_unregister_ldisc(int disc) 13496fd7ce5SGreg Kroah-Hartman { 13596fd7ce5SGreg Kroah-Hartman unsigned long flags; 13696fd7ce5SGreg Kroah-Hartman int ret = 0; 13796fd7ce5SGreg Kroah-Hartman 13896fd7ce5SGreg Kroah-Hartman if (disc < N_TTY || disc >= NR_LDISCS) 13996fd7ce5SGreg Kroah-Hartman return -EINVAL; 14096fd7ce5SGreg Kroah-Hartman 14196fd7ce5SGreg Kroah-Hartman spin_lock_irqsave(&tty_ldisc_lock, flags); 14296fd7ce5SGreg Kroah-Hartman if (tty_ldiscs[disc]->refcount) 14396fd7ce5SGreg Kroah-Hartman ret = -EBUSY; 14496fd7ce5SGreg Kroah-Hartman else 14596fd7ce5SGreg Kroah-Hartman tty_ldiscs[disc] = NULL; 14696fd7ce5SGreg Kroah-Hartman spin_unlock_irqrestore(&tty_ldisc_lock, flags); 14796fd7ce5SGreg Kroah-Hartman 14896fd7ce5SGreg Kroah-Hartman return ret; 14996fd7ce5SGreg Kroah-Hartman } 15096fd7ce5SGreg Kroah-Hartman EXPORT_SYMBOL(tty_unregister_ldisc); 15196fd7ce5SGreg Kroah-Hartman 15296fd7ce5SGreg Kroah-Hartman static struct tty_ldisc_ops *get_ldops(int disc) 15396fd7ce5SGreg Kroah-Hartman { 15496fd7ce5SGreg Kroah-Hartman unsigned long flags; 15596fd7ce5SGreg Kroah-Hartman struct tty_ldisc_ops *ldops, *ret; 15696fd7ce5SGreg Kroah-Hartman 15796fd7ce5SGreg Kroah-Hartman spin_lock_irqsave(&tty_ldisc_lock, flags); 15896fd7ce5SGreg Kroah-Hartman ret = ERR_PTR(-EINVAL); 15996fd7ce5SGreg Kroah-Hartman ldops = tty_ldiscs[disc]; 16096fd7ce5SGreg Kroah-Hartman if (ldops) { 16196fd7ce5SGreg Kroah-Hartman ret = ERR_PTR(-EAGAIN); 16296fd7ce5SGreg Kroah-Hartman if (try_module_get(ldops->owner)) { 16396fd7ce5SGreg Kroah-Hartman ldops->refcount++; 16496fd7ce5SGreg Kroah-Hartman ret = ldops; 16596fd7ce5SGreg Kroah-Hartman } 16696fd7ce5SGreg Kroah-Hartman } 16796fd7ce5SGreg Kroah-Hartman spin_unlock_irqrestore(&tty_ldisc_lock, flags); 16896fd7ce5SGreg Kroah-Hartman return ret; 16996fd7ce5SGreg Kroah-Hartman } 17096fd7ce5SGreg Kroah-Hartman 17196fd7ce5SGreg Kroah-Hartman static void put_ldops(struct tty_ldisc_ops *ldops) 17296fd7ce5SGreg Kroah-Hartman { 17396fd7ce5SGreg Kroah-Hartman unsigned long flags; 17496fd7ce5SGreg Kroah-Hartman 17596fd7ce5SGreg Kroah-Hartman spin_lock_irqsave(&tty_ldisc_lock, flags); 17696fd7ce5SGreg Kroah-Hartman ldops->refcount--; 17796fd7ce5SGreg Kroah-Hartman module_put(ldops->owner); 17896fd7ce5SGreg Kroah-Hartman spin_unlock_irqrestore(&tty_ldisc_lock, flags); 17996fd7ce5SGreg Kroah-Hartman } 18096fd7ce5SGreg Kroah-Hartman 18196fd7ce5SGreg Kroah-Hartman /** 18296fd7ce5SGreg Kroah-Hartman * tty_ldisc_get - take a reference to an ldisc 18396fd7ce5SGreg Kroah-Hartman * @disc: ldisc number 18496fd7ce5SGreg Kroah-Hartman * 18596fd7ce5SGreg Kroah-Hartman * Takes a reference to a line discipline. Deals with refcounts and 18696fd7ce5SGreg Kroah-Hartman * module locking counts. Returns NULL if the discipline is not available. 18796fd7ce5SGreg Kroah-Hartman * Returns a pointer to the discipline and bumps the ref count if it is 18896fd7ce5SGreg Kroah-Hartman * available 18996fd7ce5SGreg Kroah-Hartman * 19096fd7ce5SGreg Kroah-Hartman * Locking: 19196fd7ce5SGreg Kroah-Hartman * takes tty_ldisc_lock to guard against ldisc races 19296fd7ce5SGreg Kroah-Hartman */ 19396fd7ce5SGreg Kroah-Hartman 19496fd7ce5SGreg Kroah-Hartman static struct tty_ldisc *tty_ldisc_get(int disc) 19596fd7ce5SGreg Kroah-Hartman { 19696fd7ce5SGreg Kroah-Hartman struct tty_ldisc *ld; 19796fd7ce5SGreg Kroah-Hartman struct tty_ldisc_ops *ldops; 19896fd7ce5SGreg Kroah-Hartman 19996fd7ce5SGreg Kroah-Hartman if (disc < N_TTY || disc >= NR_LDISCS) 20096fd7ce5SGreg Kroah-Hartman return ERR_PTR(-EINVAL); 20196fd7ce5SGreg Kroah-Hartman 20296fd7ce5SGreg Kroah-Hartman /* 20396fd7ce5SGreg Kroah-Hartman * Get the ldisc ops - we may need to request them to be loaded 20496fd7ce5SGreg Kroah-Hartman * dynamically and try again. 20596fd7ce5SGreg Kroah-Hartman */ 20696fd7ce5SGreg Kroah-Hartman ldops = get_ldops(disc); 20796fd7ce5SGreg Kroah-Hartman if (IS_ERR(ldops)) { 20896fd7ce5SGreg Kroah-Hartman request_module("tty-ldisc-%d", disc); 20996fd7ce5SGreg Kroah-Hartman ldops = get_ldops(disc); 21096fd7ce5SGreg Kroah-Hartman if (IS_ERR(ldops)) 21196fd7ce5SGreg Kroah-Hartman return ERR_CAST(ldops); 21296fd7ce5SGreg Kroah-Hartman } 21396fd7ce5SGreg Kroah-Hartman 21496fd7ce5SGreg Kroah-Hartman ld = kmalloc(sizeof(struct tty_ldisc), GFP_KERNEL); 21596fd7ce5SGreg Kroah-Hartman if (ld == NULL) { 21696fd7ce5SGreg Kroah-Hartman put_ldops(ldops); 21796fd7ce5SGreg Kroah-Hartman return ERR_PTR(-ENOMEM); 21896fd7ce5SGreg Kroah-Hartman } 21996fd7ce5SGreg Kroah-Hartman 22096fd7ce5SGreg Kroah-Hartman ld->ops = ldops; 22196fd7ce5SGreg Kroah-Hartman atomic_set(&ld->users, 1); 22296fd7ce5SGreg Kroah-Hartman return ld; 22396fd7ce5SGreg Kroah-Hartman } 22496fd7ce5SGreg Kroah-Hartman 22596fd7ce5SGreg Kroah-Hartman static void *tty_ldiscs_seq_start(struct seq_file *m, loff_t *pos) 22696fd7ce5SGreg Kroah-Hartman { 22796fd7ce5SGreg Kroah-Hartman return (*pos < NR_LDISCS) ? pos : NULL; 22896fd7ce5SGreg Kroah-Hartman } 22996fd7ce5SGreg Kroah-Hartman 23096fd7ce5SGreg Kroah-Hartman static void *tty_ldiscs_seq_next(struct seq_file *m, void *v, loff_t *pos) 23196fd7ce5SGreg Kroah-Hartman { 23296fd7ce5SGreg Kroah-Hartman (*pos)++; 23396fd7ce5SGreg Kroah-Hartman return (*pos < NR_LDISCS) ? pos : NULL; 23496fd7ce5SGreg Kroah-Hartman } 23596fd7ce5SGreg Kroah-Hartman 23696fd7ce5SGreg Kroah-Hartman static void tty_ldiscs_seq_stop(struct seq_file *m, void *v) 23796fd7ce5SGreg Kroah-Hartman { 23896fd7ce5SGreg Kroah-Hartman } 23996fd7ce5SGreg Kroah-Hartman 24096fd7ce5SGreg Kroah-Hartman static int tty_ldiscs_seq_show(struct seq_file *m, void *v) 24196fd7ce5SGreg Kroah-Hartman { 24296fd7ce5SGreg Kroah-Hartman int i = *(loff_t *)v; 24396fd7ce5SGreg Kroah-Hartman struct tty_ldisc_ops *ldops; 24496fd7ce5SGreg Kroah-Hartman 24596fd7ce5SGreg Kroah-Hartman ldops = get_ldops(i); 24696fd7ce5SGreg Kroah-Hartman if (IS_ERR(ldops)) 24796fd7ce5SGreg Kroah-Hartman return 0; 24896fd7ce5SGreg Kroah-Hartman seq_printf(m, "%-10s %2d\n", ldops->name ? ldops->name : "???", i); 24996fd7ce5SGreg Kroah-Hartman put_ldops(ldops); 25096fd7ce5SGreg Kroah-Hartman return 0; 25196fd7ce5SGreg Kroah-Hartman } 25296fd7ce5SGreg Kroah-Hartman 25396fd7ce5SGreg Kroah-Hartman static const struct seq_operations tty_ldiscs_seq_ops = { 25496fd7ce5SGreg Kroah-Hartman .start = tty_ldiscs_seq_start, 25596fd7ce5SGreg Kroah-Hartman .next = tty_ldiscs_seq_next, 25696fd7ce5SGreg Kroah-Hartman .stop = tty_ldiscs_seq_stop, 25796fd7ce5SGreg Kroah-Hartman .show = tty_ldiscs_seq_show, 25896fd7ce5SGreg Kroah-Hartman }; 25996fd7ce5SGreg Kroah-Hartman 26096fd7ce5SGreg Kroah-Hartman static int proc_tty_ldiscs_open(struct inode *inode, struct file *file) 26196fd7ce5SGreg Kroah-Hartman { 26296fd7ce5SGreg Kroah-Hartman return seq_open(file, &tty_ldiscs_seq_ops); 26396fd7ce5SGreg Kroah-Hartman } 26496fd7ce5SGreg Kroah-Hartman 26596fd7ce5SGreg Kroah-Hartman const struct file_operations tty_ldiscs_proc_fops = { 26696fd7ce5SGreg Kroah-Hartman .owner = THIS_MODULE, 26796fd7ce5SGreg Kroah-Hartman .open = proc_tty_ldiscs_open, 26896fd7ce5SGreg Kroah-Hartman .read = seq_read, 26996fd7ce5SGreg Kroah-Hartman .llseek = seq_lseek, 27096fd7ce5SGreg Kroah-Hartman .release = seq_release, 27196fd7ce5SGreg Kroah-Hartman }; 27296fd7ce5SGreg Kroah-Hartman 27396fd7ce5SGreg Kroah-Hartman /** 27496fd7ce5SGreg Kroah-Hartman * tty_ldisc_assign - set ldisc on a tty 27596fd7ce5SGreg Kroah-Hartman * @tty: tty to assign 27696fd7ce5SGreg Kroah-Hartman * @ld: line discipline 27796fd7ce5SGreg Kroah-Hartman * 27896fd7ce5SGreg Kroah-Hartman * Install an instance of a line discipline into a tty structure. The 27996fd7ce5SGreg Kroah-Hartman * ldisc must have a reference count above zero to ensure it remains. 28096fd7ce5SGreg Kroah-Hartman * The tty instance refcount starts at zero. 28196fd7ce5SGreg Kroah-Hartman * 28296fd7ce5SGreg Kroah-Hartman * Locking: 28396fd7ce5SGreg Kroah-Hartman * Caller must hold references 28496fd7ce5SGreg Kroah-Hartman */ 28596fd7ce5SGreg Kroah-Hartman 28696fd7ce5SGreg Kroah-Hartman static void tty_ldisc_assign(struct tty_struct *tty, struct tty_ldisc *ld) 28796fd7ce5SGreg Kroah-Hartman { 28896fd7ce5SGreg Kroah-Hartman tty->ldisc = ld; 28996fd7ce5SGreg Kroah-Hartman } 29096fd7ce5SGreg Kroah-Hartman 29196fd7ce5SGreg Kroah-Hartman /** 29296fd7ce5SGreg Kroah-Hartman * tty_ldisc_try - internal helper 29396fd7ce5SGreg Kroah-Hartman * @tty: the tty 29496fd7ce5SGreg Kroah-Hartman * 29596fd7ce5SGreg Kroah-Hartman * Make a single attempt to grab and bump the refcount on 29696fd7ce5SGreg Kroah-Hartman * the tty ldisc. Return 0 on failure or 1 on success. This is 29796fd7ce5SGreg Kroah-Hartman * used to implement both the waiting and non waiting versions 29896fd7ce5SGreg Kroah-Hartman * of tty_ldisc_ref 29996fd7ce5SGreg Kroah-Hartman * 30096fd7ce5SGreg Kroah-Hartman * Locking: takes tty_ldisc_lock 30196fd7ce5SGreg Kroah-Hartman */ 30296fd7ce5SGreg Kroah-Hartman 30396fd7ce5SGreg Kroah-Hartman static struct tty_ldisc *tty_ldisc_try(struct tty_struct *tty) 30496fd7ce5SGreg Kroah-Hartman { 30596fd7ce5SGreg Kroah-Hartman unsigned long flags; 30696fd7ce5SGreg Kroah-Hartman struct tty_ldisc *ld; 30796fd7ce5SGreg Kroah-Hartman 30896fd7ce5SGreg Kroah-Hartman spin_lock_irqsave(&tty_ldisc_lock, flags); 30996fd7ce5SGreg Kroah-Hartman ld = NULL; 31096fd7ce5SGreg Kroah-Hartman if (test_bit(TTY_LDISC, &tty->flags)) 31196fd7ce5SGreg Kroah-Hartman ld = get_ldisc(tty->ldisc); 31296fd7ce5SGreg Kroah-Hartman spin_unlock_irqrestore(&tty_ldisc_lock, flags); 31396fd7ce5SGreg Kroah-Hartman return ld; 31496fd7ce5SGreg Kroah-Hartman } 31596fd7ce5SGreg Kroah-Hartman 31696fd7ce5SGreg Kroah-Hartman /** 31796fd7ce5SGreg Kroah-Hartman * tty_ldisc_ref_wait - wait for the tty ldisc 31896fd7ce5SGreg Kroah-Hartman * @tty: tty device 31996fd7ce5SGreg Kroah-Hartman * 32096fd7ce5SGreg Kroah-Hartman * Dereference the line discipline for the terminal and take a 32196fd7ce5SGreg Kroah-Hartman * reference to it. If the line discipline is in flux then 32296fd7ce5SGreg Kroah-Hartman * wait patiently until it changes. 32396fd7ce5SGreg Kroah-Hartman * 32496fd7ce5SGreg Kroah-Hartman * Note: Must not be called from an IRQ/timer context. The caller 32596fd7ce5SGreg Kroah-Hartman * must also be careful not to hold other locks that will deadlock 32696fd7ce5SGreg Kroah-Hartman * against a discipline change, such as an existing ldisc reference 32796fd7ce5SGreg Kroah-Hartman * (which we check for) 32896fd7ce5SGreg Kroah-Hartman * 32996fd7ce5SGreg Kroah-Hartman * Locking: call functions take tty_ldisc_lock 33096fd7ce5SGreg Kroah-Hartman */ 33196fd7ce5SGreg Kroah-Hartman 33296fd7ce5SGreg Kroah-Hartman struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty) 33396fd7ce5SGreg Kroah-Hartman { 33496fd7ce5SGreg Kroah-Hartman struct tty_ldisc *ld; 33596fd7ce5SGreg Kroah-Hartman 33696fd7ce5SGreg Kroah-Hartman /* wait_event is a macro */ 33796fd7ce5SGreg Kroah-Hartman wait_event(tty_ldisc_wait, (ld = tty_ldisc_try(tty)) != NULL); 33896fd7ce5SGreg Kroah-Hartman return ld; 33996fd7ce5SGreg Kroah-Hartman } 34096fd7ce5SGreg Kroah-Hartman EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait); 34196fd7ce5SGreg Kroah-Hartman 34296fd7ce5SGreg Kroah-Hartman /** 34396fd7ce5SGreg Kroah-Hartman * tty_ldisc_ref - get the tty ldisc 34496fd7ce5SGreg Kroah-Hartman * @tty: tty device 34596fd7ce5SGreg Kroah-Hartman * 34696fd7ce5SGreg Kroah-Hartman * Dereference the line discipline for the terminal and take a 34796fd7ce5SGreg Kroah-Hartman * reference to it. If the line discipline is in flux then 34896fd7ce5SGreg Kroah-Hartman * return NULL. Can be called from IRQ and timer functions. 34996fd7ce5SGreg Kroah-Hartman * 35096fd7ce5SGreg Kroah-Hartman * Locking: called functions take tty_ldisc_lock 35196fd7ce5SGreg Kroah-Hartman */ 35296fd7ce5SGreg Kroah-Hartman 35396fd7ce5SGreg Kroah-Hartman struct tty_ldisc *tty_ldisc_ref(struct tty_struct *tty) 35496fd7ce5SGreg Kroah-Hartman { 35596fd7ce5SGreg Kroah-Hartman return tty_ldisc_try(tty); 35696fd7ce5SGreg Kroah-Hartman } 35796fd7ce5SGreg Kroah-Hartman EXPORT_SYMBOL_GPL(tty_ldisc_ref); 35896fd7ce5SGreg Kroah-Hartman 35996fd7ce5SGreg Kroah-Hartman /** 36096fd7ce5SGreg Kroah-Hartman * tty_ldisc_deref - free a tty ldisc reference 36196fd7ce5SGreg Kroah-Hartman * @ld: reference to free up 36296fd7ce5SGreg Kroah-Hartman * 36396fd7ce5SGreg Kroah-Hartman * Undoes the effect of tty_ldisc_ref or tty_ldisc_ref_wait. May 36496fd7ce5SGreg Kroah-Hartman * be called in IRQ context. 36596fd7ce5SGreg Kroah-Hartman * 36696fd7ce5SGreg Kroah-Hartman * Locking: takes tty_ldisc_lock 36796fd7ce5SGreg Kroah-Hartman */ 36896fd7ce5SGreg Kroah-Hartman 36996fd7ce5SGreg Kroah-Hartman void tty_ldisc_deref(struct tty_ldisc *ld) 37096fd7ce5SGreg Kroah-Hartman { 37196fd7ce5SGreg Kroah-Hartman put_ldisc(ld); 37296fd7ce5SGreg Kroah-Hartman } 37396fd7ce5SGreg Kroah-Hartman EXPORT_SYMBOL_GPL(tty_ldisc_deref); 37496fd7ce5SGreg Kroah-Hartman 37596fd7ce5SGreg Kroah-Hartman static inline void tty_ldisc_put(struct tty_ldisc *ld) 37696fd7ce5SGreg Kroah-Hartman { 37796fd7ce5SGreg Kroah-Hartman put_ldisc(ld); 37896fd7ce5SGreg Kroah-Hartman } 37996fd7ce5SGreg Kroah-Hartman 38096fd7ce5SGreg Kroah-Hartman /** 38196fd7ce5SGreg Kroah-Hartman * tty_ldisc_enable - allow ldisc use 38296fd7ce5SGreg Kroah-Hartman * @tty: terminal to activate ldisc on 38396fd7ce5SGreg Kroah-Hartman * 38496fd7ce5SGreg Kroah-Hartman * Set the TTY_LDISC flag when the line discipline can be called 38596fd7ce5SGreg Kroah-Hartman * again. Do necessary wakeups for existing sleepers. Clear the LDISC 38696fd7ce5SGreg Kroah-Hartman * changing flag to indicate any ldisc change is now over. 38796fd7ce5SGreg Kroah-Hartman * 38896fd7ce5SGreg Kroah-Hartman * Note: nobody should set the TTY_LDISC bit except via this function. 38996fd7ce5SGreg Kroah-Hartman * Clearing directly is allowed. 39096fd7ce5SGreg Kroah-Hartman */ 39196fd7ce5SGreg Kroah-Hartman 39296fd7ce5SGreg Kroah-Hartman void tty_ldisc_enable(struct tty_struct *tty) 39396fd7ce5SGreg Kroah-Hartman { 39496fd7ce5SGreg Kroah-Hartman set_bit(TTY_LDISC, &tty->flags); 39596fd7ce5SGreg Kroah-Hartman clear_bit(TTY_LDISC_CHANGING, &tty->flags); 39696fd7ce5SGreg Kroah-Hartman wake_up(&tty_ldisc_wait); 39796fd7ce5SGreg Kroah-Hartman } 39896fd7ce5SGreg Kroah-Hartman 39996fd7ce5SGreg Kroah-Hartman /** 40096fd7ce5SGreg Kroah-Hartman * tty_ldisc_flush - flush line discipline queue 40196fd7ce5SGreg Kroah-Hartman * @tty: tty 40296fd7ce5SGreg Kroah-Hartman * 40396fd7ce5SGreg Kroah-Hartman * Flush the line discipline queue (if any) for this tty. If there 40496fd7ce5SGreg Kroah-Hartman * is no line discipline active this is a no-op. 40596fd7ce5SGreg Kroah-Hartman */ 40696fd7ce5SGreg Kroah-Hartman 40796fd7ce5SGreg Kroah-Hartman void tty_ldisc_flush(struct tty_struct *tty) 40896fd7ce5SGreg Kroah-Hartman { 40996fd7ce5SGreg Kroah-Hartman struct tty_ldisc *ld = tty_ldisc_ref(tty); 41096fd7ce5SGreg Kroah-Hartman if (ld) { 41196fd7ce5SGreg Kroah-Hartman if (ld->ops->flush_buffer) 41296fd7ce5SGreg Kroah-Hartman ld->ops->flush_buffer(tty); 41396fd7ce5SGreg Kroah-Hartman tty_ldisc_deref(ld); 41496fd7ce5SGreg Kroah-Hartman } 41596fd7ce5SGreg Kroah-Hartman tty_buffer_flush(tty); 41696fd7ce5SGreg Kroah-Hartman } 41796fd7ce5SGreg Kroah-Hartman EXPORT_SYMBOL_GPL(tty_ldisc_flush); 41896fd7ce5SGreg Kroah-Hartman 41996fd7ce5SGreg Kroah-Hartman /** 42096fd7ce5SGreg Kroah-Hartman * tty_set_termios_ldisc - set ldisc field 42196fd7ce5SGreg Kroah-Hartman * @tty: tty structure 42296fd7ce5SGreg Kroah-Hartman * @num: line discipline number 42396fd7ce5SGreg Kroah-Hartman * 42496fd7ce5SGreg Kroah-Hartman * This is probably overkill for real world processors but 42596fd7ce5SGreg Kroah-Hartman * they are not on hot paths so a little discipline won't do 42696fd7ce5SGreg Kroah-Hartman * any harm. 42796fd7ce5SGreg Kroah-Hartman * 42896fd7ce5SGreg Kroah-Hartman * Locking: takes termios_mutex 42996fd7ce5SGreg Kroah-Hartman */ 43096fd7ce5SGreg Kroah-Hartman 43196fd7ce5SGreg Kroah-Hartman static void tty_set_termios_ldisc(struct tty_struct *tty, int num) 43296fd7ce5SGreg Kroah-Hartman { 43396fd7ce5SGreg Kroah-Hartman mutex_lock(&tty->termios_mutex); 43496fd7ce5SGreg Kroah-Hartman tty->termios->c_line = num; 43596fd7ce5SGreg Kroah-Hartman mutex_unlock(&tty->termios_mutex); 43696fd7ce5SGreg Kroah-Hartman } 43796fd7ce5SGreg Kroah-Hartman 43896fd7ce5SGreg Kroah-Hartman /** 43996fd7ce5SGreg Kroah-Hartman * tty_ldisc_open - open a line discipline 44096fd7ce5SGreg Kroah-Hartman * @tty: tty we are opening the ldisc on 44196fd7ce5SGreg Kroah-Hartman * @ld: discipline to open 44296fd7ce5SGreg Kroah-Hartman * 44396fd7ce5SGreg Kroah-Hartman * A helper opening method. Also a convenient debugging and check 44496fd7ce5SGreg Kroah-Hartman * point. 44596fd7ce5SGreg Kroah-Hartman * 44696fd7ce5SGreg Kroah-Hartman * Locking: always called with BTM already held. 44796fd7ce5SGreg Kroah-Hartman */ 44896fd7ce5SGreg Kroah-Hartman 44996fd7ce5SGreg Kroah-Hartman static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld) 45096fd7ce5SGreg Kroah-Hartman { 45196fd7ce5SGreg Kroah-Hartman WARN_ON(test_and_set_bit(TTY_LDISC_OPEN, &tty->flags)); 45296fd7ce5SGreg Kroah-Hartman if (ld->ops->open) { 45396fd7ce5SGreg Kroah-Hartman int ret; 45496fd7ce5SGreg Kroah-Hartman /* BTM here locks versus a hangup event */ 45596fd7ce5SGreg Kroah-Hartman WARN_ON(!tty_locked()); 45696fd7ce5SGreg Kroah-Hartman ret = ld->ops->open(tty); 45796fd7ce5SGreg Kroah-Hartman return ret; 45896fd7ce5SGreg Kroah-Hartman } 45996fd7ce5SGreg Kroah-Hartman return 0; 46096fd7ce5SGreg Kroah-Hartman } 46196fd7ce5SGreg Kroah-Hartman 46296fd7ce5SGreg Kroah-Hartman /** 46396fd7ce5SGreg Kroah-Hartman * tty_ldisc_close - close a line discipline 46496fd7ce5SGreg Kroah-Hartman * @tty: tty we are opening the ldisc on 46596fd7ce5SGreg Kroah-Hartman * @ld: discipline to close 46696fd7ce5SGreg Kroah-Hartman * 46796fd7ce5SGreg Kroah-Hartman * A helper close method. Also a convenient debugging and check 46896fd7ce5SGreg Kroah-Hartman * point. 46996fd7ce5SGreg Kroah-Hartman */ 47096fd7ce5SGreg Kroah-Hartman 47196fd7ce5SGreg Kroah-Hartman static void tty_ldisc_close(struct tty_struct *tty, struct tty_ldisc *ld) 47296fd7ce5SGreg Kroah-Hartman { 47396fd7ce5SGreg Kroah-Hartman WARN_ON(!test_bit(TTY_LDISC_OPEN, &tty->flags)); 47496fd7ce5SGreg Kroah-Hartman clear_bit(TTY_LDISC_OPEN, &tty->flags); 47596fd7ce5SGreg Kroah-Hartman if (ld->ops->close) 47696fd7ce5SGreg Kroah-Hartman ld->ops->close(tty); 47796fd7ce5SGreg Kroah-Hartman } 47896fd7ce5SGreg Kroah-Hartman 47996fd7ce5SGreg Kroah-Hartman /** 48096fd7ce5SGreg Kroah-Hartman * tty_ldisc_restore - helper for tty ldisc change 48196fd7ce5SGreg Kroah-Hartman * @tty: tty to recover 48296fd7ce5SGreg Kroah-Hartman * @old: previous ldisc 48396fd7ce5SGreg Kroah-Hartman * 48496fd7ce5SGreg Kroah-Hartman * Restore the previous line discipline or N_TTY when a line discipline 48596fd7ce5SGreg Kroah-Hartman * change fails due to an open error 48696fd7ce5SGreg Kroah-Hartman */ 48796fd7ce5SGreg Kroah-Hartman 48896fd7ce5SGreg Kroah-Hartman static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old) 48996fd7ce5SGreg Kroah-Hartman { 49096fd7ce5SGreg Kroah-Hartman char buf[64]; 49196fd7ce5SGreg Kroah-Hartman struct tty_ldisc *new_ldisc; 49296fd7ce5SGreg Kroah-Hartman int r; 49396fd7ce5SGreg Kroah-Hartman 49496fd7ce5SGreg Kroah-Hartman /* There is an outstanding reference here so this is safe */ 49596fd7ce5SGreg Kroah-Hartman old = tty_ldisc_get(old->ops->num); 49696fd7ce5SGreg Kroah-Hartman WARN_ON(IS_ERR(old)); 49796fd7ce5SGreg Kroah-Hartman tty_ldisc_assign(tty, old); 49896fd7ce5SGreg Kroah-Hartman tty_set_termios_ldisc(tty, old->ops->num); 49996fd7ce5SGreg Kroah-Hartman if (tty_ldisc_open(tty, old) < 0) { 50096fd7ce5SGreg Kroah-Hartman tty_ldisc_put(old); 50196fd7ce5SGreg Kroah-Hartman /* This driver is always present */ 50296fd7ce5SGreg Kroah-Hartman new_ldisc = tty_ldisc_get(N_TTY); 50396fd7ce5SGreg Kroah-Hartman if (IS_ERR(new_ldisc)) 50496fd7ce5SGreg Kroah-Hartman panic("n_tty: get"); 50596fd7ce5SGreg Kroah-Hartman tty_ldisc_assign(tty, new_ldisc); 50696fd7ce5SGreg Kroah-Hartman tty_set_termios_ldisc(tty, N_TTY); 50796fd7ce5SGreg Kroah-Hartman r = tty_ldisc_open(tty, new_ldisc); 50896fd7ce5SGreg Kroah-Hartman if (r < 0) 50996fd7ce5SGreg Kroah-Hartman panic("Couldn't open N_TTY ldisc for " 51096fd7ce5SGreg Kroah-Hartman "%s --- error %d.", 51196fd7ce5SGreg Kroah-Hartman tty_name(tty, buf), r); 51296fd7ce5SGreg Kroah-Hartman } 51396fd7ce5SGreg Kroah-Hartman } 51496fd7ce5SGreg Kroah-Hartman 51596fd7ce5SGreg Kroah-Hartman /** 51696fd7ce5SGreg Kroah-Hartman * tty_ldisc_halt - shut down the line discipline 51796fd7ce5SGreg Kroah-Hartman * @tty: tty device 51896fd7ce5SGreg Kroah-Hartman * 51996fd7ce5SGreg Kroah-Hartman * Shut down the line discipline and work queue for this tty device. 52096fd7ce5SGreg Kroah-Hartman * The TTY_LDISC flag being cleared ensures no further references can 52196fd7ce5SGreg Kroah-Hartman * be obtained while the delayed work queue halt ensures that no more 52296fd7ce5SGreg Kroah-Hartman * data is fed to the ldisc. 52396fd7ce5SGreg Kroah-Hartman * 52496fd7ce5SGreg Kroah-Hartman * You need to do a 'flush_scheduled_work()' (outside the ldisc_mutex) 52596fd7ce5SGreg Kroah-Hartman * in order to make sure any currently executing ldisc work is also 52696fd7ce5SGreg Kroah-Hartman * flushed. 52796fd7ce5SGreg Kroah-Hartman */ 52896fd7ce5SGreg Kroah-Hartman 52996fd7ce5SGreg Kroah-Hartman static int tty_ldisc_halt(struct tty_struct *tty) 53096fd7ce5SGreg Kroah-Hartman { 53196fd7ce5SGreg Kroah-Hartman clear_bit(TTY_LDISC, &tty->flags); 53296fd7ce5SGreg Kroah-Hartman return cancel_delayed_work_sync(&tty->buf.work); 53396fd7ce5SGreg Kroah-Hartman } 53496fd7ce5SGreg Kroah-Hartman 53596fd7ce5SGreg Kroah-Hartman /** 536100eeae2SJiri Slaby * tty_ldisc_wait_idle - wait for the ldisc to become idle 537100eeae2SJiri Slaby * @tty: tty to wait for 538100eeae2SJiri Slaby * 539100eeae2SJiri Slaby * Wait for the line discipline to become idle. The discipline must 540100eeae2SJiri Slaby * have been halted for this to guarantee it remains idle. 541100eeae2SJiri Slaby */ 542100eeae2SJiri Slaby static int tty_ldisc_wait_idle(struct tty_struct *tty) 543100eeae2SJiri Slaby { 544100eeae2SJiri Slaby int ret; 545100eeae2SJiri Slaby ret = wait_event_interruptible_timeout(tty_ldisc_idle, 546100eeae2SJiri Slaby atomic_read(&tty->ldisc->users) == 1, 5 * HZ); 547100eeae2SJiri Slaby if (ret < 0) 548100eeae2SJiri Slaby return ret; 549100eeae2SJiri Slaby return ret > 0 ? 0 : -EBUSY; 550100eeae2SJiri Slaby } 551100eeae2SJiri Slaby 552100eeae2SJiri Slaby /** 55396fd7ce5SGreg Kroah-Hartman * tty_set_ldisc - set line discipline 55496fd7ce5SGreg Kroah-Hartman * @tty: the terminal to set 55596fd7ce5SGreg Kroah-Hartman * @ldisc: the line discipline 55696fd7ce5SGreg Kroah-Hartman * 55796fd7ce5SGreg Kroah-Hartman * Set the discipline of a tty line. Must be called from a process 55896fd7ce5SGreg Kroah-Hartman * context. The ldisc change logic has to protect itself against any 55996fd7ce5SGreg Kroah-Hartman * overlapping ldisc change (including on the other end of pty pairs), 56096fd7ce5SGreg Kroah-Hartman * the close of one side of a tty/pty pair, and eventually hangup. 56196fd7ce5SGreg Kroah-Hartman * 56296fd7ce5SGreg Kroah-Hartman * Locking: takes tty_ldisc_lock, termios_mutex 56396fd7ce5SGreg Kroah-Hartman */ 56496fd7ce5SGreg Kroah-Hartman 56596fd7ce5SGreg Kroah-Hartman int tty_set_ldisc(struct tty_struct *tty, int ldisc) 56696fd7ce5SGreg Kroah-Hartman { 56796fd7ce5SGreg Kroah-Hartman int retval; 56896fd7ce5SGreg Kroah-Hartman struct tty_ldisc *o_ldisc, *new_ldisc; 56996fd7ce5SGreg Kroah-Hartman int work, o_work = 0; 57096fd7ce5SGreg Kroah-Hartman struct tty_struct *o_tty; 57196fd7ce5SGreg Kroah-Hartman 57296fd7ce5SGreg Kroah-Hartman new_ldisc = tty_ldisc_get(ldisc); 57396fd7ce5SGreg Kroah-Hartman if (IS_ERR(new_ldisc)) 57496fd7ce5SGreg Kroah-Hartman return PTR_ERR(new_ldisc); 57596fd7ce5SGreg Kroah-Hartman 57696fd7ce5SGreg Kroah-Hartman tty_lock(); 57796fd7ce5SGreg Kroah-Hartman /* 57896fd7ce5SGreg Kroah-Hartman * We need to look at the tty locking here for pty/tty pairs 57996fd7ce5SGreg Kroah-Hartman * when both sides try to change in parallel. 58096fd7ce5SGreg Kroah-Hartman */ 58196fd7ce5SGreg Kroah-Hartman 58296fd7ce5SGreg Kroah-Hartman o_tty = tty->link; /* o_tty is the pty side or NULL */ 58396fd7ce5SGreg Kroah-Hartman 58496fd7ce5SGreg Kroah-Hartman 58596fd7ce5SGreg Kroah-Hartman /* 58696fd7ce5SGreg Kroah-Hartman * Check the no-op case 58796fd7ce5SGreg Kroah-Hartman */ 58896fd7ce5SGreg Kroah-Hartman 58996fd7ce5SGreg Kroah-Hartman if (tty->ldisc->ops->num == ldisc) { 59096fd7ce5SGreg Kroah-Hartman tty_unlock(); 59196fd7ce5SGreg Kroah-Hartman tty_ldisc_put(new_ldisc); 59296fd7ce5SGreg Kroah-Hartman return 0; 59396fd7ce5SGreg Kroah-Hartman } 59496fd7ce5SGreg Kroah-Hartman 59596fd7ce5SGreg Kroah-Hartman tty_unlock(); 59696fd7ce5SGreg Kroah-Hartman /* 59796fd7ce5SGreg Kroah-Hartman * Problem: What do we do if this blocks ? 59896fd7ce5SGreg Kroah-Hartman * We could deadlock here 59996fd7ce5SGreg Kroah-Hartman */ 60096fd7ce5SGreg Kroah-Hartman 60196fd7ce5SGreg Kroah-Hartman tty_wait_until_sent(tty, 0); 60296fd7ce5SGreg Kroah-Hartman 60396fd7ce5SGreg Kroah-Hartman tty_lock(); 60496fd7ce5SGreg Kroah-Hartman mutex_lock(&tty->ldisc_mutex); 60596fd7ce5SGreg Kroah-Hartman 60696fd7ce5SGreg Kroah-Hartman /* 60796fd7ce5SGreg Kroah-Hartman * We could be midstream of another ldisc change which has 60896fd7ce5SGreg Kroah-Hartman * dropped the lock during processing. If so we need to wait. 60996fd7ce5SGreg Kroah-Hartman */ 61096fd7ce5SGreg Kroah-Hartman 61196fd7ce5SGreg Kroah-Hartman while (test_bit(TTY_LDISC_CHANGING, &tty->flags)) { 61296fd7ce5SGreg Kroah-Hartman mutex_unlock(&tty->ldisc_mutex); 61396fd7ce5SGreg Kroah-Hartman tty_unlock(); 61496fd7ce5SGreg Kroah-Hartman wait_event(tty_ldisc_wait, 61596fd7ce5SGreg Kroah-Hartman test_bit(TTY_LDISC_CHANGING, &tty->flags) == 0); 61696fd7ce5SGreg Kroah-Hartman tty_lock(); 61796fd7ce5SGreg Kroah-Hartman mutex_lock(&tty->ldisc_mutex); 61896fd7ce5SGreg Kroah-Hartman } 61996fd7ce5SGreg Kroah-Hartman 62096fd7ce5SGreg Kroah-Hartman set_bit(TTY_LDISC_CHANGING, &tty->flags); 62196fd7ce5SGreg Kroah-Hartman 62296fd7ce5SGreg Kroah-Hartman /* 62396fd7ce5SGreg Kroah-Hartman * No more input please, we are switching. The new ldisc 62496fd7ce5SGreg Kroah-Hartman * will update this value in the ldisc open function 62596fd7ce5SGreg Kroah-Hartman */ 62696fd7ce5SGreg Kroah-Hartman 62796fd7ce5SGreg Kroah-Hartman tty->receive_room = 0; 62896fd7ce5SGreg Kroah-Hartman 62996fd7ce5SGreg Kroah-Hartman o_ldisc = tty->ldisc; 63096fd7ce5SGreg Kroah-Hartman 63196fd7ce5SGreg Kroah-Hartman tty_unlock(); 63296fd7ce5SGreg Kroah-Hartman /* 63396fd7ce5SGreg Kroah-Hartman * Make sure we don't change while someone holds a 63496fd7ce5SGreg Kroah-Hartman * reference to the line discipline. The TTY_LDISC bit 63596fd7ce5SGreg Kroah-Hartman * prevents anyone taking a reference once it is clear. 63696fd7ce5SGreg Kroah-Hartman * We need the lock to avoid racing reference takers. 63796fd7ce5SGreg Kroah-Hartman * 63896fd7ce5SGreg Kroah-Hartman * We must clear the TTY_LDISC bit here to avoid a livelock 63996fd7ce5SGreg Kroah-Hartman * with a userspace app continually trying to use the tty in 64096fd7ce5SGreg Kroah-Hartman * parallel to the change and re-referencing the tty. 64196fd7ce5SGreg Kroah-Hartman */ 64296fd7ce5SGreg Kroah-Hartman 64396fd7ce5SGreg Kroah-Hartman work = tty_ldisc_halt(tty); 64496fd7ce5SGreg Kroah-Hartman if (o_tty) 64596fd7ce5SGreg Kroah-Hartman o_work = tty_ldisc_halt(o_tty); 64696fd7ce5SGreg Kroah-Hartman 64796fd7ce5SGreg Kroah-Hartman /* 64896fd7ce5SGreg Kroah-Hartman * Wait for ->hangup_work and ->buf.work handlers to terminate. 64996fd7ce5SGreg Kroah-Hartman * We must drop the mutex here in case a hangup is also in process. 65096fd7ce5SGreg Kroah-Hartman */ 65196fd7ce5SGreg Kroah-Hartman 65296fd7ce5SGreg Kroah-Hartman mutex_unlock(&tty->ldisc_mutex); 65396fd7ce5SGreg Kroah-Hartman 65496fd7ce5SGreg Kroah-Hartman flush_scheduled_work(); 65596fd7ce5SGreg Kroah-Hartman 656100eeae2SJiri Slaby retval = tty_ldisc_wait_idle(tty); 657100eeae2SJiri Slaby 65896fd7ce5SGreg Kroah-Hartman tty_lock(); 65996fd7ce5SGreg Kroah-Hartman mutex_lock(&tty->ldisc_mutex); 660100eeae2SJiri Slaby 661100eeae2SJiri Slaby /* handle wait idle failure locked */ 662100eeae2SJiri Slaby if (retval) { 663100eeae2SJiri Slaby tty_ldisc_put(new_ldisc); 664100eeae2SJiri Slaby goto enable; 665100eeae2SJiri Slaby } 666100eeae2SJiri Slaby 66796fd7ce5SGreg Kroah-Hartman if (test_bit(TTY_HUPPED, &tty->flags)) { 66896fd7ce5SGreg Kroah-Hartman /* We were raced by the hangup method. It will have stomped 66996fd7ce5SGreg Kroah-Hartman the ldisc data and closed the ldisc down */ 67096fd7ce5SGreg Kroah-Hartman clear_bit(TTY_LDISC_CHANGING, &tty->flags); 67196fd7ce5SGreg Kroah-Hartman mutex_unlock(&tty->ldisc_mutex); 67296fd7ce5SGreg Kroah-Hartman tty_ldisc_put(new_ldisc); 67396fd7ce5SGreg Kroah-Hartman tty_unlock(); 67496fd7ce5SGreg Kroah-Hartman return -EIO; 67596fd7ce5SGreg Kroah-Hartman } 67696fd7ce5SGreg Kroah-Hartman 67796fd7ce5SGreg Kroah-Hartman /* Shutdown the current discipline. */ 67896fd7ce5SGreg Kroah-Hartman tty_ldisc_close(tty, o_ldisc); 67996fd7ce5SGreg Kroah-Hartman 68096fd7ce5SGreg Kroah-Hartman /* Now set up the new line discipline. */ 68196fd7ce5SGreg Kroah-Hartman tty_ldisc_assign(tty, new_ldisc); 68296fd7ce5SGreg Kroah-Hartman tty_set_termios_ldisc(tty, ldisc); 68396fd7ce5SGreg Kroah-Hartman 68496fd7ce5SGreg Kroah-Hartman retval = tty_ldisc_open(tty, new_ldisc); 68596fd7ce5SGreg Kroah-Hartman if (retval < 0) { 68696fd7ce5SGreg Kroah-Hartman /* Back to the old one or N_TTY if we can't */ 68796fd7ce5SGreg Kroah-Hartman tty_ldisc_put(new_ldisc); 68896fd7ce5SGreg Kroah-Hartman tty_ldisc_restore(tty, o_ldisc); 68996fd7ce5SGreg Kroah-Hartman } 69096fd7ce5SGreg Kroah-Hartman 69196fd7ce5SGreg Kroah-Hartman /* At this point we hold a reference to the new ldisc and a 69296fd7ce5SGreg Kroah-Hartman a reference to the old ldisc. If we ended up flipping back 69396fd7ce5SGreg Kroah-Hartman to the existing ldisc we have two references to it */ 69496fd7ce5SGreg Kroah-Hartman 69596fd7ce5SGreg Kroah-Hartman if (tty->ldisc->ops->num != o_ldisc->ops->num && tty->ops->set_ldisc) 69696fd7ce5SGreg Kroah-Hartman tty->ops->set_ldisc(tty); 69796fd7ce5SGreg Kroah-Hartman 69896fd7ce5SGreg Kroah-Hartman tty_ldisc_put(o_ldisc); 69996fd7ce5SGreg Kroah-Hartman 700100eeae2SJiri Slaby enable: 70196fd7ce5SGreg Kroah-Hartman /* 70296fd7ce5SGreg Kroah-Hartman * Allow ldisc referencing to occur again 70396fd7ce5SGreg Kroah-Hartman */ 70496fd7ce5SGreg Kroah-Hartman 70596fd7ce5SGreg Kroah-Hartman tty_ldisc_enable(tty); 70696fd7ce5SGreg Kroah-Hartman if (o_tty) 70796fd7ce5SGreg Kroah-Hartman tty_ldisc_enable(o_tty); 70896fd7ce5SGreg Kroah-Hartman 70996fd7ce5SGreg Kroah-Hartman /* Restart the work queue in case no characters kick it off. Safe if 71096fd7ce5SGreg Kroah-Hartman already running */ 71196fd7ce5SGreg Kroah-Hartman if (work) 71296fd7ce5SGreg Kroah-Hartman schedule_delayed_work(&tty->buf.work, 1); 71396fd7ce5SGreg Kroah-Hartman if (o_work) 71496fd7ce5SGreg Kroah-Hartman schedule_delayed_work(&o_tty->buf.work, 1); 71596fd7ce5SGreg Kroah-Hartman mutex_unlock(&tty->ldisc_mutex); 71696fd7ce5SGreg Kroah-Hartman tty_unlock(); 71796fd7ce5SGreg Kroah-Hartman return retval; 71896fd7ce5SGreg Kroah-Hartman } 71996fd7ce5SGreg Kroah-Hartman 72096fd7ce5SGreg Kroah-Hartman /** 72196fd7ce5SGreg Kroah-Hartman * tty_reset_termios - reset terminal state 72296fd7ce5SGreg Kroah-Hartman * @tty: tty to reset 72396fd7ce5SGreg Kroah-Hartman * 72496fd7ce5SGreg Kroah-Hartman * Restore a terminal to the driver default state. 72596fd7ce5SGreg Kroah-Hartman */ 72696fd7ce5SGreg Kroah-Hartman 72796fd7ce5SGreg Kroah-Hartman static void tty_reset_termios(struct tty_struct *tty) 72896fd7ce5SGreg Kroah-Hartman { 72996fd7ce5SGreg Kroah-Hartman mutex_lock(&tty->termios_mutex); 73096fd7ce5SGreg Kroah-Hartman *tty->termios = tty->driver->init_termios; 73196fd7ce5SGreg Kroah-Hartman tty->termios->c_ispeed = tty_termios_input_baud_rate(tty->termios); 73296fd7ce5SGreg Kroah-Hartman tty->termios->c_ospeed = tty_termios_baud_rate(tty->termios); 73396fd7ce5SGreg Kroah-Hartman mutex_unlock(&tty->termios_mutex); 73496fd7ce5SGreg Kroah-Hartman } 73596fd7ce5SGreg Kroah-Hartman 73696fd7ce5SGreg Kroah-Hartman 73796fd7ce5SGreg Kroah-Hartman /** 73896fd7ce5SGreg Kroah-Hartman * tty_ldisc_reinit - reinitialise the tty ldisc 73996fd7ce5SGreg Kroah-Hartman * @tty: tty to reinit 74096fd7ce5SGreg Kroah-Hartman * @ldisc: line discipline to reinitialize 74196fd7ce5SGreg Kroah-Hartman * 74296fd7ce5SGreg Kroah-Hartman * Switch the tty to a line discipline and leave the ldisc 74396fd7ce5SGreg Kroah-Hartman * state closed 74496fd7ce5SGreg Kroah-Hartman */ 74596fd7ce5SGreg Kroah-Hartman 74696fd7ce5SGreg Kroah-Hartman static void tty_ldisc_reinit(struct tty_struct *tty, int ldisc) 74796fd7ce5SGreg Kroah-Hartman { 74896fd7ce5SGreg Kroah-Hartman struct tty_ldisc *ld; 74996fd7ce5SGreg Kroah-Hartman 75096fd7ce5SGreg Kroah-Hartman tty_ldisc_close(tty, tty->ldisc); 75196fd7ce5SGreg Kroah-Hartman tty_ldisc_put(tty->ldisc); 75296fd7ce5SGreg Kroah-Hartman tty->ldisc = NULL; 75396fd7ce5SGreg Kroah-Hartman /* 75496fd7ce5SGreg Kroah-Hartman * Switch the line discipline back 75596fd7ce5SGreg Kroah-Hartman */ 75696fd7ce5SGreg Kroah-Hartman ld = tty_ldisc_get(ldisc); 75796fd7ce5SGreg Kroah-Hartman BUG_ON(IS_ERR(ld)); 75896fd7ce5SGreg Kroah-Hartman tty_ldisc_assign(tty, ld); 75996fd7ce5SGreg Kroah-Hartman tty_set_termios_ldisc(tty, ldisc); 76096fd7ce5SGreg Kroah-Hartman } 76196fd7ce5SGreg Kroah-Hartman 76296fd7ce5SGreg Kroah-Hartman /** 76396fd7ce5SGreg Kroah-Hartman * tty_ldisc_hangup - hangup ldisc reset 76496fd7ce5SGreg Kroah-Hartman * @tty: tty being hung up 76596fd7ce5SGreg Kroah-Hartman * 76696fd7ce5SGreg Kroah-Hartman * Some tty devices reset their termios when they receive a hangup 76796fd7ce5SGreg Kroah-Hartman * event. In that situation we must also switch back to N_TTY properly 76896fd7ce5SGreg Kroah-Hartman * before we reset the termios data. 76996fd7ce5SGreg Kroah-Hartman * 77096fd7ce5SGreg Kroah-Hartman * Locking: We can take the ldisc mutex as the rest of the code is 77196fd7ce5SGreg Kroah-Hartman * careful to allow for this. 77296fd7ce5SGreg Kroah-Hartman * 77396fd7ce5SGreg Kroah-Hartman * In the pty pair case this occurs in the close() path of the 77496fd7ce5SGreg Kroah-Hartman * tty itself so we must be careful about locking rules. 77596fd7ce5SGreg Kroah-Hartman */ 77696fd7ce5SGreg Kroah-Hartman 77796fd7ce5SGreg Kroah-Hartman void tty_ldisc_hangup(struct tty_struct *tty) 77896fd7ce5SGreg Kroah-Hartman { 77996fd7ce5SGreg Kroah-Hartman struct tty_ldisc *ld; 78096fd7ce5SGreg Kroah-Hartman int reset = tty->driver->flags & TTY_DRIVER_RESET_TERMIOS; 78196fd7ce5SGreg Kroah-Hartman int err = 0; 78296fd7ce5SGreg Kroah-Hartman 78396fd7ce5SGreg Kroah-Hartman /* 78496fd7ce5SGreg Kroah-Hartman * FIXME! What are the locking issues here? This may me overdoing 78596fd7ce5SGreg Kroah-Hartman * things... This question is especially important now that we've 78696fd7ce5SGreg Kroah-Hartman * removed the irqlock. 78796fd7ce5SGreg Kroah-Hartman */ 78896fd7ce5SGreg Kroah-Hartman ld = tty_ldisc_ref(tty); 78996fd7ce5SGreg Kroah-Hartman if (ld != NULL) { 79096fd7ce5SGreg Kroah-Hartman /* We may have no line discipline at this point */ 79196fd7ce5SGreg Kroah-Hartman if (ld->ops->flush_buffer) 79296fd7ce5SGreg Kroah-Hartman ld->ops->flush_buffer(tty); 79396fd7ce5SGreg Kroah-Hartman tty_driver_flush_buffer(tty); 79496fd7ce5SGreg Kroah-Hartman if ((test_bit(TTY_DO_WRITE_WAKEUP, &tty->flags)) && 79596fd7ce5SGreg Kroah-Hartman ld->ops->write_wakeup) 79696fd7ce5SGreg Kroah-Hartman ld->ops->write_wakeup(tty); 79796fd7ce5SGreg Kroah-Hartman if (ld->ops->hangup) 79896fd7ce5SGreg Kroah-Hartman ld->ops->hangup(tty); 79996fd7ce5SGreg Kroah-Hartman tty_ldisc_deref(ld); 80096fd7ce5SGreg Kroah-Hartman } 80196fd7ce5SGreg Kroah-Hartman /* 80296fd7ce5SGreg Kroah-Hartman * FIXME: Once we trust the LDISC code better we can wait here for 80396fd7ce5SGreg Kroah-Hartman * ldisc completion and fix the driver call race 80496fd7ce5SGreg Kroah-Hartman */ 80596fd7ce5SGreg Kroah-Hartman wake_up_interruptible_poll(&tty->write_wait, POLLOUT); 80696fd7ce5SGreg Kroah-Hartman wake_up_interruptible_poll(&tty->read_wait, POLLIN); 80796fd7ce5SGreg Kroah-Hartman /* 80896fd7ce5SGreg Kroah-Hartman * Shutdown the current line discipline, and reset it to 80996fd7ce5SGreg Kroah-Hartman * N_TTY if need be. 81096fd7ce5SGreg Kroah-Hartman * 81196fd7ce5SGreg Kroah-Hartman * Avoid racing set_ldisc or tty_ldisc_release 81296fd7ce5SGreg Kroah-Hartman */ 81396fd7ce5SGreg Kroah-Hartman mutex_lock(&tty->ldisc_mutex); 81496fd7ce5SGreg Kroah-Hartman 81596fd7ce5SGreg Kroah-Hartman /* 81696fd7ce5SGreg Kroah-Hartman * this is like tty_ldisc_halt, but we need to give up 81796fd7ce5SGreg Kroah-Hartman * the BTM before calling cancel_delayed_work_sync, 81896fd7ce5SGreg Kroah-Hartman * which may need to wait for another function taking the BTM 81996fd7ce5SGreg Kroah-Hartman */ 82096fd7ce5SGreg Kroah-Hartman clear_bit(TTY_LDISC, &tty->flags); 82196fd7ce5SGreg Kroah-Hartman tty_unlock(); 82296fd7ce5SGreg Kroah-Hartman cancel_delayed_work_sync(&tty->buf.work); 82396fd7ce5SGreg Kroah-Hartman mutex_unlock(&tty->ldisc_mutex); 82496fd7ce5SGreg Kroah-Hartman 82596fd7ce5SGreg Kroah-Hartman tty_lock(); 82696fd7ce5SGreg Kroah-Hartman mutex_lock(&tty->ldisc_mutex); 82796fd7ce5SGreg Kroah-Hartman 82896fd7ce5SGreg Kroah-Hartman /* At this point we have a closed ldisc and we want to 82996fd7ce5SGreg Kroah-Hartman reopen it. We could defer this to the next open but 83096fd7ce5SGreg Kroah-Hartman it means auditing a lot of other paths so this is 83196fd7ce5SGreg Kroah-Hartman a FIXME */ 83296fd7ce5SGreg Kroah-Hartman if (tty->ldisc) { /* Not yet closed */ 83396fd7ce5SGreg Kroah-Hartman if (reset == 0) { 83496fd7ce5SGreg Kroah-Hartman tty_ldisc_reinit(tty, tty->termios->c_line); 83596fd7ce5SGreg Kroah-Hartman err = tty_ldisc_open(tty, tty->ldisc); 83696fd7ce5SGreg Kroah-Hartman } 83796fd7ce5SGreg Kroah-Hartman /* If the re-open fails or we reset then go to N_TTY. The 83896fd7ce5SGreg Kroah-Hartman N_TTY open cannot fail */ 83996fd7ce5SGreg Kroah-Hartman if (reset || err) { 84096fd7ce5SGreg Kroah-Hartman tty_ldisc_reinit(tty, N_TTY); 84196fd7ce5SGreg Kroah-Hartman WARN_ON(tty_ldisc_open(tty, tty->ldisc)); 84296fd7ce5SGreg Kroah-Hartman } 84396fd7ce5SGreg Kroah-Hartman tty_ldisc_enable(tty); 84496fd7ce5SGreg Kroah-Hartman } 84596fd7ce5SGreg Kroah-Hartman mutex_unlock(&tty->ldisc_mutex); 84696fd7ce5SGreg Kroah-Hartman if (reset) 84796fd7ce5SGreg Kroah-Hartman tty_reset_termios(tty); 84896fd7ce5SGreg Kroah-Hartman } 84996fd7ce5SGreg Kroah-Hartman 85096fd7ce5SGreg Kroah-Hartman /** 85196fd7ce5SGreg Kroah-Hartman * tty_ldisc_setup - open line discipline 85296fd7ce5SGreg Kroah-Hartman * @tty: tty being shut down 85396fd7ce5SGreg Kroah-Hartman * @o_tty: pair tty for pty/tty pairs 85496fd7ce5SGreg Kroah-Hartman * 85596fd7ce5SGreg Kroah-Hartman * Called during the initial open of a tty/pty pair in order to set up the 85696fd7ce5SGreg Kroah-Hartman * line disciplines and bind them to the tty. This has no locking issues 85796fd7ce5SGreg Kroah-Hartman * as the device isn't yet active. 85896fd7ce5SGreg Kroah-Hartman */ 85996fd7ce5SGreg Kroah-Hartman 86096fd7ce5SGreg Kroah-Hartman int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty) 86196fd7ce5SGreg Kroah-Hartman { 86296fd7ce5SGreg Kroah-Hartman struct tty_ldisc *ld = tty->ldisc; 86396fd7ce5SGreg Kroah-Hartman int retval; 86496fd7ce5SGreg Kroah-Hartman 86596fd7ce5SGreg Kroah-Hartman retval = tty_ldisc_open(tty, ld); 86696fd7ce5SGreg Kroah-Hartman if (retval) 86796fd7ce5SGreg Kroah-Hartman return retval; 86896fd7ce5SGreg Kroah-Hartman 86996fd7ce5SGreg Kroah-Hartman if (o_tty) { 87096fd7ce5SGreg Kroah-Hartman retval = tty_ldisc_open(o_tty, o_tty->ldisc); 87196fd7ce5SGreg Kroah-Hartman if (retval) { 87296fd7ce5SGreg Kroah-Hartman tty_ldisc_close(tty, ld); 87396fd7ce5SGreg Kroah-Hartman return retval; 87496fd7ce5SGreg Kroah-Hartman } 87596fd7ce5SGreg Kroah-Hartman tty_ldisc_enable(o_tty); 87696fd7ce5SGreg Kroah-Hartman } 87796fd7ce5SGreg Kroah-Hartman tty_ldisc_enable(tty); 87896fd7ce5SGreg Kroah-Hartman return 0; 87996fd7ce5SGreg Kroah-Hartman } 88096fd7ce5SGreg Kroah-Hartman /** 88196fd7ce5SGreg Kroah-Hartman * tty_ldisc_release - release line discipline 88296fd7ce5SGreg Kroah-Hartman * @tty: tty being shut down 88396fd7ce5SGreg Kroah-Hartman * @o_tty: pair tty for pty/tty pairs 88496fd7ce5SGreg Kroah-Hartman * 88596fd7ce5SGreg Kroah-Hartman * Called during the final close of a tty/pty pair in order to shut down 88696fd7ce5SGreg Kroah-Hartman * the line discpline layer. On exit the ldisc assigned is N_TTY and the 88796fd7ce5SGreg Kroah-Hartman * ldisc has not been opened. 88896fd7ce5SGreg Kroah-Hartman */ 88996fd7ce5SGreg Kroah-Hartman 89096fd7ce5SGreg Kroah-Hartman void tty_ldisc_release(struct tty_struct *tty, struct tty_struct *o_tty) 89196fd7ce5SGreg Kroah-Hartman { 89296fd7ce5SGreg Kroah-Hartman /* 89396fd7ce5SGreg Kroah-Hartman * Prevent flush_to_ldisc() from rescheduling the work for later. Then 89496fd7ce5SGreg Kroah-Hartman * kill any delayed work. As this is the final close it does not 89596fd7ce5SGreg Kroah-Hartman * race with the set_ldisc code path. 89696fd7ce5SGreg Kroah-Hartman */ 89796fd7ce5SGreg Kroah-Hartman 89896fd7ce5SGreg Kroah-Hartman tty_unlock(); 89996fd7ce5SGreg Kroah-Hartman tty_ldisc_halt(tty); 90096fd7ce5SGreg Kroah-Hartman flush_scheduled_work(); 90196fd7ce5SGreg Kroah-Hartman tty_lock(); 90296fd7ce5SGreg Kroah-Hartman 90396fd7ce5SGreg Kroah-Hartman mutex_lock(&tty->ldisc_mutex); 90496fd7ce5SGreg Kroah-Hartman /* 90596fd7ce5SGreg Kroah-Hartman * Now kill off the ldisc 90696fd7ce5SGreg Kroah-Hartman */ 90796fd7ce5SGreg Kroah-Hartman tty_ldisc_close(tty, tty->ldisc); 90896fd7ce5SGreg Kroah-Hartman tty_ldisc_put(tty->ldisc); 90996fd7ce5SGreg Kroah-Hartman /* Force an oops if we mess this up */ 91096fd7ce5SGreg Kroah-Hartman tty->ldisc = NULL; 91196fd7ce5SGreg Kroah-Hartman 91296fd7ce5SGreg Kroah-Hartman /* Ensure the next open requests the N_TTY ldisc */ 91396fd7ce5SGreg Kroah-Hartman tty_set_termios_ldisc(tty, N_TTY); 91496fd7ce5SGreg Kroah-Hartman mutex_unlock(&tty->ldisc_mutex); 91596fd7ce5SGreg Kroah-Hartman 91696fd7ce5SGreg Kroah-Hartman /* This will need doing differently if we need to lock */ 91796fd7ce5SGreg Kroah-Hartman if (o_tty) 91896fd7ce5SGreg Kroah-Hartman tty_ldisc_release(o_tty, NULL); 91996fd7ce5SGreg Kroah-Hartman 92096fd7ce5SGreg Kroah-Hartman /* And the memory resources remaining (buffers, termios) will be 92196fd7ce5SGreg Kroah-Hartman disposed of when the kref hits zero */ 92296fd7ce5SGreg Kroah-Hartman } 92396fd7ce5SGreg Kroah-Hartman 92496fd7ce5SGreg Kroah-Hartman /** 92596fd7ce5SGreg Kroah-Hartman * tty_ldisc_init - ldisc setup for new tty 92696fd7ce5SGreg Kroah-Hartman * @tty: tty being allocated 92796fd7ce5SGreg Kroah-Hartman * 92896fd7ce5SGreg Kroah-Hartman * Set up the line discipline objects for a newly allocated tty. Note that 92996fd7ce5SGreg Kroah-Hartman * the tty structure is not completely set up when this call is made. 93096fd7ce5SGreg Kroah-Hartman */ 93196fd7ce5SGreg Kroah-Hartman 93296fd7ce5SGreg Kroah-Hartman void tty_ldisc_init(struct tty_struct *tty) 93396fd7ce5SGreg Kroah-Hartman { 93496fd7ce5SGreg Kroah-Hartman struct tty_ldisc *ld = tty_ldisc_get(N_TTY); 93596fd7ce5SGreg Kroah-Hartman if (IS_ERR(ld)) 93696fd7ce5SGreg Kroah-Hartman panic("n_tty: init_tty"); 93796fd7ce5SGreg Kroah-Hartman tty_ldisc_assign(tty, ld); 93896fd7ce5SGreg Kroah-Hartman } 93996fd7ce5SGreg Kroah-Hartman 94096fd7ce5SGreg Kroah-Hartman void tty_ldisc_begin(void) 94196fd7ce5SGreg Kroah-Hartman { 94296fd7ce5SGreg Kroah-Hartman /* Setup the default TTY line discipline. */ 94396fd7ce5SGreg Kroah-Hartman (void) tty_register_ldisc(N_TTY, &tty_ldisc_N_TTY); 94496fd7ce5SGreg Kroah-Hartman } 945