diff options
Diffstat (limited to 'drivers/char/tty_ldisc.c')
| -rw-r--r-- | drivers/char/tty_ldisc.c | 915 |
1 files changed, 0 insertions, 915 deletions
diff --git a/drivers/char/tty_ldisc.c b/drivers/char/tty_ldisc.c deleted file mode 100644 index 412f9775d19c..000000000000 --- a/drivers/char/tty_ldisc.c +++ /dev/null @@ -1,915 +0,0 @@ -#include <linux/types.h> -#include <linux/major.h> -#include <linux/errno.h> -#include <linux/signal.h> -#include <linux/fcntl.h> -#include <linux/sched.h> -#include <linux/interrupt.h> -#include <linux/tty.h> -#include <linux/tty_driver.h> -#include <linux/tty_flip.h> -#include <linux/devpts_fs.h> -#include <linux/file.h> -#include <linux/console.h> -#include <linux/timer.h> -#include <linux/ctype.h> -#include <linux/kd.h> -#include <linux/mm.h> -#include <linux/string.h> -#include <linux/slab.h> -#include <linux/poll.h> -#include <linux/proc_fs.h> -#include <linux/init.h> -#include <linux/module.h> -#include <linux/device.h> -#include <linux/wait.h> -#include <linux/bitops.h> -#include <linux/delay.h> -#include <linux/seq_file.h> - -#include <linux/uaccess.h> -#include <asm/system.h> - -#include <linux/kbd_kern.h> -#include <linux/vt_kern.h> -#include <linux/selection.h> - -#include <linux/smp_lock.h> /* For the moment */ - -#include <linux/kmod.h> -#include <linux/nsproxy.h> - -/* - * This guards the refcounted line discipline lists. The lock - * must be taken with irqs off because there are hangup path - * callers who will do ldisc lookups and cannot sleep. - */ - -static DEFINE_SPINLOCK(tty_ldisc_lock); -static DECLARE_WAIT_QUEUE_HEAD(tty_ldisc_wait); -/* Line disc dispatch table */ -static struct tty_ldisc_ops *tty_ldiscs[NR_LDISCS]; - -static inline struct tty_ldisc *get_ldisc(struct tty_ldisc *ld) -{ - if (ld) - atomic_inc(&ld->users); - return ld; -} - -static void put_ldisc(struct tty_ldisc *ld) -{ - unsigned long flags; - - if (WARN_ON_ONCE(!ld)) - return; - - /* - * If this is the last user, free the ldisc, and - * release the ldisc ops. - * - * We really want an "atomic_dec_and_lock_irqsave()", - * but we don't have it, so this does it by hand. - */ - local_irq_save(flags); - if (atomic_dec_and_lock(&ld->users, &tty_ldisc_lock)) { - struct tty_ldisc_ops *ldo = ld->ops; - - ldo->refcount--; - module_put(ldo->owner); - spin_unlock_irqrestore(&tty_ldisc_lock, flags); - - kfree(ld); - return; - } - local_irq_restore(flags); -} - -/** - * tty_register_ldisc - install a line discipline - * @disc: ldisc number - * @new_ldisc: pointer to the ldisc object - * - * Installs a new line discipline into the kernel. The discipline - * is set up as unreferenced and then made available to the kernel - * from this point onwards. - * - * Locking: - * takes tty_ldisc_lock to guard against ldisc races - */ - -int tty_register_ldisc(int disc, struct tty_ldisc_ops *new_ldisc) -{ - unsigned long flags; - int ret = 0; - - if (disc < N_TTY || disc >= NR_LDISCS) - return -EINVAL; - - spin_lock_irqsave(&tty_ldisc_lock, flags); - tty_ldiscs[disc] = new_ldisc; - new_ldisc->num = disc; - new_ldisc->refcount = 0; - spin_unlock_irqrestore(&tty_ldisc_lock, flags); - - return ret; -} -EXPORT_SYMBOL(tty_register_ldisc); - -/** - * tty_unregister_ldisc - unload a line discipline - * @disc: ldisc number - * @new_ldisc: pointer to the ldisc object - * - * Remove a line discipline from the kernel providing it is not - * currently in use. - * - * Locking: - * takes tty_ldisc_lock to guard against ldisc races - */ - -int tty_unregister_ldisc(int disc) -{ - unsigned long flags; - int ret = 0; - - if (disc < N_TTY || disc >= NR_LDISCS) - return -EINVAL; - - spin_lock_irqsave(&tty_ldisc_lock, flags); - if (tty_ldiscs[disc]->refcount) - ret = -EBUSY; - else - tty_ldiscs[disc] = NULL; - spin_unlock_irqrestore(&tty_ldisc_lock, flags); - - return ret; -} -EXPORT_SYMBOL(tty_unregister_ldisc); - -static struct tty_ldisc_ops *get_ldops(int disc) -{ - unsigned long flags; - struct tty_ldisc_ops *ldops, *ret; - - spin_lock_irqsave(&tty_ldisc_lock, flags); - ret = ERR_PTR(-EINVAL); - ldops = tty_ldiscs[disc]; - if (ldops) { - ret = ERR_PTR(-EAGAIN); - if (try_module_get(ldops->owner)) { - ldops->refcount++; - ret = ldops; - } - } - spin_unlock_irqrestore(&tty_ldisc_lock, flags); - return ret; -} - -static void put_ldops(struct tty_ldisc_ops *ldops) -{ - unsigned long flags; - - spin_lock_irqsave(&tty_ldisc_lock, flags); - ldops->refcount--; - module_put(ldops->owner); - spin_unlock_irqrestore(&tty_ldisc_lock, flags); -} - -/** - * tty_ldisc_get - take a reference to an ldisc - * @disc: ldisc number - * - * Takes a reference to a line discipline. Deals with refcounts and - * module locking counts. Returns NULL if the discipline is not available. - * Returns a pointer to the discipline and bumps the ref count if it is - * available - * - * Locking: - * takes tty_ldisc_lock to guard against ldisc races - */ - -static struct tty_ldisc *tty_ldisc_get(int disc) -{ - struct tty_ldisc *ld; - struct tty_ldisc_ops *ldops; - - if (disc < N_TTY || disc >= NR_LDISCS) - return ERR_PTR(-EINVAL); - - /* - * Get the ldisc ops - we may need to request them to be loaded - * dynamically and try again. - */ - ldops = get_ldops(disc); - if (IS_ERR(ldops)) { - request_module("tty-ldisc-%d", disc); - ldops = get_ldops(disc); - if (IS_ERR(ldops)) - return ERR_CAST(ldops); - } - - ld = kmalloc(sizeof(struct tty_ldisc), GFP_KERNEL); - if (ld == NULL) { - put_ldops(ldops); - return ERR_PTR(-ENOMEM); - } - - ld->ops = ldops; - atomic_set(&ld->users, 1); - return ld; -} - -static void *tty_ldiscs_seq_start(struct seq_file *m, loff_t *pos) -{ - return (*pos < NR_LDISCS) ? pos : NULL; -} - -static void *tty_ldiscs_seq_next(struct seq_file *m, void *v, loff_t *pos) -{ - (*pos)++; - return (*pos < NR_LDISCS) ? pos : NULL; -} - -static void tty_ldiscs_seq_stop(struct seq_file *m, void *v) -{ -} - -static int tty_ldiscs_seq_show(struct seq_file *m, void *v) -{ - int i = *(loff_t *)v; - struct tty_ldisc_ops *ldops; - - ldops = get_ldops(i); - if (IS_ERR(ldops)) - return 0; - seq_printf(m, "%-10s %2d\n", ldops->name ? ldops->name : "???", i); - put_ldops(ldops); - return 0; -} - -static const struct seq_operations tty_ldiscs_seq_ops = { - .start = tty_ldiscs_seq_start, - .next = tty_ldiscs_seq_next, - .stop = tty_ldiscs_seq_stop, - .show = tty_ldiscs_seq_show, -}; - -static int proc_tty_ldiscs_open(struct inode *inode, struct file *file) -{ - return seq_open(file, &tty_ldiscs_seq_ops); -} - -const struct file_operations tty_ldiscs_proc_fops = { - .owner = THIS_MODULE, - .open = proc_tty_ldiscs_open, - .read = seq_read, - .llseek = seq_lseek, - .release = seq_release, -}; - -/** - * tty_ldisc_assign - set ldisc on a tty - * @tty: tty to assign - * @ld: line discipline - * - * Install an instance of a line discipline into a tty structure. The - * ldisc must have a reference count above zero to ensure it remains. - * The tty instance refcount starts at zero. - * - * Locking: - * Caller must hold references - */ - -static void tty_ldisc_assign(struct tty_struct *tty, struct tty_ldisc *ld) -{ - tty->ldisc = ld; -} - -/** - * tty_ldisc_try - internal helper - * @tty: the tty - * - * Make a single attempt to grab and bump the refcount on - * the tty ldisc. Return 0 on failure or 1 on success. This is - * used to implement both the waiting and non waiting versions - * of tty_ldisc_ref - * - * Locking: takes tty_ldisc_lock - */ - -static struct tty_ldisc *tty_ldisc_try(struct tty_struct *tty) -{ - unsigned long flags; - struct tty_ldisc *ld; - - spin_lock_irqsave(&tty_ldisc_lock, flags); - ld = NULL; - if (test_bit(TTY_LDISC, &tty->flags)) - ld = get_ldisc(tty->ldisc); - spin_unlock_irqrestore(&tty_ldisc_lock, flags); - return ld; -} - -/** - * tty_ldisc_ref_wait - wait for the tty ldisc - * @tty: tty device - * - * Dereference the line discipline for the terminal and take a - * reference to it. If the line discipline is in flux then - * wait patiently until it changes. - * - * Note: Must not be called from an IRQ/timer context. The caller - * must also be careful not to hold other locks that will deadlock - * against a discipline change, such as an existing ldisc reference - * (which we check for) - * - * Locking: call functions take tty_ldisc_lock - */ - -struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty) -{ - struct tty_ldisc *ld; - - /* wait_event is a macro */ - wait_event(tty_ldisc_wait, (ld = tty_ldisc_try(tty)) != NULL); - return ld; -} -EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait); - -/** - * tty_ldisc_ref - get the tty ldisc - * @tty: tty device - * - * Dereference the line discipline for the terminal and take a - * reference to it. If the line discipline is in flux then - * return NULL. Can be called from IRQ and timer functions. - * - * Locking: called functions take tty_ldisc_lock - */ - -struct tty_ldisc *tty_ldisc_ref(struct tty_struct *tty) -{ - return tty_ldisc_try(tty); -} -EXPORT_SYMBOL_GPL(tty_ldisc_ref); - -/** - * tty_ldisc_deref - free a tty ldisc reference - * @ld: reference to free up - * - * Undoes the effect of tty_ldisc_ref or tty_ldisc_ref_wait. May - * be called in IRQ context. - * - * Locking: takes tty_ldisc_lock - */ - -void tty_ldisc_deref(struct tty_ldisc *ld) -{ - put_ldisc(ld); -} -EXPORT_SYMBOL_GPL(tty_ldisc_deref); - -static inline void tty_ldisc_put(struct tty_ldisc *ld) -{ - put_ldisc(ld); -} - -/** - * tty_ldisc_enable - allow ldisc use - * @tty: terminal to activate ldisc on - * - * Set the TTY_LDISC flag when the line discipline can be called - * again. Do necessary wakeups for existing sleepers. Clear the LDISC - * changing flag to indicate any ldisc change is now over. - * - * Note: nobody should set the TTY_LDISC bit except via this function. - * Clearing directly is allowed. - */ - -void tty_ldisc_enable(struct tty_struct *tty) -{ - set_bit(TTY_LDISC, &tty->flags); - clear_bit(TTY_LDISC_CHANGING, &tty->flags); - wake_up(&tty_ldisc_wait); -} - -/** - * tty_ldisc_flush - flush line discipline queue - * @tty: tty - * - * Flush the line discipline queue (if any) for this tty. If there - * is no line discipline active this is a no-op. - */ - -void tty_ldisc_flush(struct tty_struct *tty) -{ - struct tty_ldisc *ld = tty_ldisc_ref(tty); - if (ld) { - if (ld->ops->flush_buffer) - ld->ops->flush_buffer(tty); - tty_ldisc_deref(ld); - } - tty_buffer_flush(tty); -} -EXPORT_SYMBOL_GPL(tty_ldisc_flush); - -/** - * tty_set_termios_ldisc - set ldisc field - * @tty: tty structure - * @num: line discipline number - * - * This is probably overkill for real world processors but - * they are not on hot paths so a little discipline won't do - * any harm. - * - * Locking: takes termios_mutex - */ - -static void tty_set_termios_ldisc(struct tty_struct *tty, int num) -{ - mutex_lock(&tty->termios_mutex); - tty->termios->c_line = num; - mutex_unlock(&tty->termios_mutex); -} - -/** - * tty_ldisc_open - open a line discipline - * @tty: tty we are opening the ldisc on - * @ld: discipline to open - * - * A helper opening method. Also a convenient debugging and check - * point. - * - * Locking: always called with BTM already held. - */ - -static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld) -{ - WARN_ON(test_and_set_bit(TTY_LDISC_OPEN, &tty->flags)); - if (ld->ops->open) { - int ret; - /* BTM here locks versus a hangup event */ - WARN_ON(!tty_locked()); - ret = ld->ops->open(tty); - return ret; - } - return 0; -} - -/** - * tty_ldisc_close - close a line discipline - * @tty: tty we are opening the ldisc on - * @ld: discipline to close - * - * A helper close method. Also a convenient debugging and check - * point. - */ - -static void tty_ldisc_close(struct tty_struct *tty, struct tty_ldisc *ld) -{ - WARN_ON(!test_bit(TTY_LDISC_OPEN, &tty->flags)); - clear_bit(TTY_LDISC_OPEN, &tty->flags); - if (ld->ops->close) - ld->ops->close(tty); -} - -/** - * tty_ldisc_restore - helper for tty ldisc change - * @tty: tty to recover - * @old: previous ldisc - * - * Restore the previous line discipline or N_TTY when a line discipline - * change fails due to an open error - */ - -static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old) -{ - char buf[64]; - struct tty_ldisc *new_ldisc; - int r; - - /* There is an outstanding reference here so this is safe */ - old = tty_ldisc_get(old->ops->num); - WARN_ON(IS_ERR(old)); - tty_ldisc_assign(tty, old); - tty_set_termios_ldisc(tty, old->ops->num); - if (tty_ldisc_open(tty, old) < 0) { - tty_ldisc_put(old); - /* This driver is always present */ - new_ldisc = tty_ldisc_get(N_TTY); - if (IS_ERR(new_ldisc)) - panic("n_tty: get"); - tty_ldisc_assign(tty, new_ldisc); - tty_set_termios_ldisc(tty, N_TTY); - r = tty_ldisc_open(tty, new_ldisc); - if (r < 0) - panic("Couldn't open N_TTY ldisc for " - "%s --- error %d.", - tty_name(tty, buf), r); - } -} - -/** - * tty_ldisc_halt - shut down the line discipline - * @tty: tty device - * - * Shut down the line discipline and work queue for this tty device. - * The TTY_LDISC flag being cleared ensures no further references can - * be obtained while the delayed work queue halt ensures that no more - * data is fed to the ldisc. - * - * You need to do a 'flush_scheduled_work()' (outside the ldisc_mutex) - * in order to make sure any currently executing ldisc work is also - * flushed. - */ - -static int tty_ldisc_halt(struct tty_struct *tty) -{ - clear_bit(TTY_LDISC, &tty->flags); - return cancel_delayed_work_sync(&tty->buf.work); -} - -/** - * tty_set_ldisc - set line discipline - * @tty: the terminal to set - * @ldisc: the line discipline - * - * Set the discipline of a tty line. Must be called from a process - * context. The ldisc change logic has to protect itself against any - * overlapping ldisc change (including on the other end of pty pairs), - * the close of one side of a tty/pty pair, and eventually hangup. - * - * Locking: takes tty_ldisc_lock, termios_mutex - */ - -int tty_set_ldisc(struct tty_struct *tty, int ldisc) -{ - int retval; - struct tty_ldisc *o_ldisc, *new_ldisc; - int work, o_work = 0; - struct tty_struct *o_tty; - - new_ldisc = tty_ldisc_get(ldisc); - if (IS_ERR(new_ldisc)) - return PTR_ERR(new_ldisc); - - tty_lock(); - /* - * We need to look at the tty locking here for pty/tty pairs - * when both sides try to change in parallel. - */ - - o_tty = tty->link; /* o_tty is the pty side or NULL */ - - - /* - * Check the no-op case - */ - - if (tty->ldisc->ops->num == ldisc) { - tty_unlock(); - tty_ldisc_put(new_ldisc); - return 0; - } - - tty_unlock(); - /* - * Problem: What do we do if this blocks ? - * We could deadlock here - */ - - tty_wait_until_sent(tty, 0); - - tty_lock(); - mutex_lock(&tty->ldisc_mutex); - - /* - * We could be midstream of another ldisc change which has - * dropped the lock during processing. If so we need to wait. - */ - - while (test_bit(TTY_LDISC_CHANGING, &tty->flags)) { - mutex_unlock(&tty->ldisc_mutex); - tty_unlock(); - wait_event(tty_ldisc_wait, - test_bit(TTY_LDISC_CHANGING, &tty->flags) == 0); - tty_lock(); - mutex_lock(&tty->ldisc_mutex); - } - - set_bit(TTY_LDISC_CHANGING, &tty->flags); - - /* - * No more input please, we are switching. The new ldisc - * will update this value in the ldisc open function - */ - - tty->receive_room = 0; - - o_ldisc = tty->ldisc; - - tty_unlock(); - /* - * Make sure we don't change while someone holds a - * reference to the line discipline. The TTY_LDISC bit - * prevents anyone taking a reference once it is clear. - * We need the lock to avoid racing reference takers. - * - * We must clear the TTY_LDISC bit here to avoid a livelock - * with a userspace app continually trying to use the tty in - * parallel to the change and re-referencing the tty. - */ - - work = tty_ldisc_halt(tty); - if (o_tty) - o_work = tty_ldisc_halt(o_tty); - - /* - * Wait for ->hangup_work and ->buf.work handlers to terminate. - * We must drop the mutex here in case a hangup is also in process. - */ - - mutex_unlock(&tty->ldisc_mutex); - - flush_scheduled_work(); - - tty_lock(); - mutex_lock(&tty->ldisc_mutex); - if (test_bit(TTY_HUPPED, &tty->flags)) { - /* We were raced by the hangup method. It will have stomped - the ldisc data and closed the ldisc down */ - clear_bit(TTY_LDISC_CHANGING, &tty->flags); - mutex_unlock(&tty->ldisc_mutex); - tty_ldisc_put(new_ldisc); - tty_unlock(); - return -EIO; - } - - /* Shutdown the current discipline. */ - tty_ldisc_close(tty, o_ldisc); - - /* Now set up the new line discipline. */ - tty_ldisc_assign(tty, new_ldisc); - tty_set_termios_ldisc(tty, ldisc); - - retval = tty_ldisc_open(tty, new_ldisc); - if (retval < 0) { - /* Back to the old one or N_TTY if we can't */ - tty_ldisc_put(new_ldisc); - tty_ldisc_restore(tty, o_ldisc); - } - - /* At this point we hold a reference to the new ldisc and a - a reference to the old ldisc. If we ended up flipping back - to the existing ldisc we have two references to it */ - - if (tty->ldisc->ops->num != o_ldisc->ops->num && tty->ops->set_ldisc) - tty->ops->set_ldisc(tty); - - tty_ldisc_put(o_ldisc); - - /* - * Allow ldisc referencing to occur again - */ - - tty_ldisc_enable(tty); - if (o_tty) - tty_ldisc_enable(o_tty); - - /* Restart the work queue in case no characters kick it off. Safe if - already running */ - if (work) - schedule_delayed_work(&tty->buf.work, 1); - if (o_work) - schedule_delayed_work(&o_tty->buf.work, 1); - mutex_unlock(&tty->ldisc_mutex); - tty_unlock(); - return retval; -} - -/** - * tty_reset_termios - reset terminal state - * @tty: tty to reset - * - * Restore a terminal to the driver default state. - */ - -static void tty_reset_termios(struct tty_struct *tty) -{ - mutex_lock(&tty->termios_mutex); - *tty->termios = tty->driver->init_termios; - tty->termios->c_ispeed = tty_termios_input_baud_rate(tty->termios); - tty->termios->c_ospeed = tty_termios_baud_rate(tty->termios); - mutex_unlock(&tty->termios_mutex); -} - - -/** - * tty_ldisc_reinit - reinitialise the tty ldisc - * @tty: tty to reinit - * @ldisc: line discipline to reinitialize - * - * Switch the tty to a line discipline and leave the ldisc - * state closed - */ - -static void tty_ldisc_reinit(struct tty_struct *tty, int ldisc) -{ - struct tty_ldisc *ld; - - tty_ldisc_close(tty, tty->ldisc); - tty_ldisc_put(tty->ldisc); - tty->ldisc = NULL; - /* - * Switch the line discipline back - */ - ld = tty_ldisc_get(ldisc); - BUG_ON(IS_ERR(ld)); - tty_ldisc_assign(tty, ld); - tty_set_termios_ldisc(tty, ldisc); -} - -/** - * tty_ldisc_hangup - hangup ldisc reset - * @tty: tty being hung up - * - * Some tty devices reset their termios when they receive a hangup - * event. In that situation we must also switch back to N_TTY properly - * before we reset the termios data. - * - * Locking: We can take the ldisc mutex as the rest of the code is - * careful to allow for this. - * - * In the pty pair case this occurs in the close() path of the - * tty itself so we must be careful about locking rules. - */ - -void tty_ldisc_hangup(struct tty_struct *tty) -{ - struct tty_ldisc *ld; - int reset = tty->driver->flags & TTY_DRIVER_RESET_TERMIOS; - int err = 0; - - /* - * FIXME! What are the locking issues here? This may me overdoing - * things... This question is especially important now that we've - * removed the irqlock. - */ - ld = tty_ldisc_ref(tty); - if (ld != NULL) { - /* We may have no line discipline at this point */ - if (ld->ops->flush_buffer) - ld->ops->flush_buffer(tty); - tty_driver_flush_buffer(tty); - if ((test_bit(TTY_DO_WRITE_WAKEUP, &tty->flags)) && - ld->ops->write_wakeup) - ld->ops->write_wakeup(tty); - if (ld->ops->hangup) - ld->ops->hangup(tty); - tty_ldisc_deref(ld); - } - /* - * FIXME: Once we trust the LDISC code better we can wait here for - * ldisc completion and fix the driver call race - */ - wake_up_interruptible_poll(&tty->write_wait, POLLOUT); - wake_up_interruptible_poll(&tty->read_wait, POLLIN); - /* - * Shutdown the current line discipline, and reset it to - * N_TTY if need be. - * - * Avoid racing set_ldisc or tty_ldisc_release - */ - mutex_lock(&tty->ldisc_mutex); - - /* - * this is like tty_ldisc_halt, but we need to give up - * the BTM before calling cancel_delayed_work_sync, - * which may need to wait for another function taking the BTM - */ - clear_bit(TTY_LDISC, &tty->flags); - tty_unlock(); - cancel_delayed_work_sync(&tty->buf.work); - mutex_unlock(&tty->ldisc_mutex); - - tty_lock(); - mutex_lock(&tty->ldisc_mutex); - - /* At this point we have a closed ldisc and we want to - reopen it. We could defer this to the next open but - it means auditing a lot of other paths so this is - a FIXME */ - if (tty->ldisc) { /* Not yet closed */ - if (reset == 0) { - tty_ldisc_reinit(tty, tty->termios->c_line); - err = tty_ldisc_open(tty, tty->ldisc); - } - /* If the re-open fails or we reset then go to N_TTY. The - N_TTY open cannot fail */ - if (reset || err) { - tty_ldisc_reinit(tty, N_TTY); - WARN_ON(tty_ldisc_open(tty, tty->ldisc)); - } - tty_ldisc_enable(tty); - } - mutex_unlock(&tty->ldisc_mutex); - if (reset) - tty_reset_termios(tty); -} - -/** - * tty_ldisc_setup - open line discipline - * @tty: tty being shut down - * @o_tty: pair tty for pty/tty pairs - * - * Called during the initial open of a tty/pty pair in order to set up the - * line disciplines and bind them to the tty. This has no locking issues - * as the device isn't yet active. - */ - -int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty) -{ - struct tty_ldisc *ld = tty->ldisc; - int retval; - - retval = tty_ldisc_open(tty, ld); - if (retval) - return retval; - - if (o_tty) { - retval = tty_ldisc_open(o_tty, o_tty->ldisc); - if (retval) { - tty_ldisc_close(tty, ld); - return retval; - } - tty_ldisc_enable(o_tty); - } - tty_ldisc_enable(tty); - return 0; -} -/** - * tty_ldisc_release - release line discipline - * @tty: tty being shut down - * @o_tty: pair tty for pty/tty pairs - * - * Called during the final close of a tty/pty pair in order to shut down - * the line discpline layer. On exit the ldisc assigned is N_TTY and the - * ldisc has not been opened. - */ - -void tty_ldisc_release(struct tty_struct *tty, struct tty_struct *o_tty) -{ - /* - * Prevent flush_to_ldisc() from rescheduling the work for later. Then - * kill any delayed work. As this is the final close it does not - * race with the set_ldisc code path. - */ - - tty_unlock(); - tty_ldisc_halt(tty); - flush_scheduled_work(); - tty_lock(); - - mutex_lock(&tty->ldisc_mutex); - /* - * Now kill off the ldisc - */ - tty_ldisc_close(tty, tty->ldisc); - tty_ldisc_put(tty->ldisc); - /* Force an oops if we mess this up */ - tty->ldisc = NULL; - - /* Ensure the next open requests the N_TTY ldisc */ - tty_set_termios_ldisc(tty, N_TTY); - mutex_unlock(&tty->ldisc_mutex); - - /* This will need doing differently if we need to lock */ - if (o_tty) - tty_ldisc_release(o_tty, NULL); - - /* And the memory resources remaining (buffers, termios) will be - disposed of when the kref hits zero */ -} - -/** - * tty_ldisc_init - ldisc setup for new tty - * @tty: tty being allocated - * - * Set up the line discipline objects for a newly allocated tty. Note that - * the tty structure is not completely set up when this call is made. - */ - -void tty_ldisc_init(struct tty_struct *tty) -{ - struct tty_ldisc *ld = tty_ldisc_get(N_TTY); - if (IS_ERR(ld)) - panic("n_tty: init_tty"); - tty_ldisc_assign(tty, ld); -} - -void tty_ldisc_begin(void) -{ - /* Setup the default TTY line discipline. */ - (void) tty_register_ldisc(N_TTY, &tty_ldisc_N_TTY); -} |
