From ace9429bb58fd418f0c81d4c2835699bddf6bde6 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Thu, 11 Apr 2024 10:27:49 +0200 Subject: Adding upstream version 6.6.15. Signed-off-by: Daniel Baumann --- drivers/tty/tty_ldisc.c | 818 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 818 insertions(+) create mode 100644 drivers/tty/tty_ldisc.c (limited to 'drivers/tty/tty_ldisc.c') diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c new file mode 100644 index 000000000..3f68e213d --- /dev/null +++ b/drivers/tty/tty_ldisc.c @@ -0,0 +1,818 @@ +// SPDX-License-Identifier: GPL-2.0 +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include "tty.h" + +#undef LDISC_DEBUG_HANGUP + +#ifdef LDISC_DEBUG_HANGUP +#define tty_ldisc_debug(tty, f, args...) tty_debug(tty, f, ##args) +#else +#define tty_ldisc_debug(tty, f, args...) +#endif + +/* lockdep nested classes for tty->ldisc_sem */ +enum { + LDISC_SEM_NORMAL, + LDISC_SEM_OTHER, +}; + + +/* + * 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_RAW_SPINLOCK(tty_ldiscs_lock); +/* Line disc dispatch table */ +static struct tty_ldisc_ops *tty_ldiscs[NR_LDISCS]; + +/** + * tty_register_ldisc - install a line discipline + * @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_ldiscs_lock to guard against ldisc races + */ +int tty_register_ldisc(struct tty_ldisc_ops *new_ldisc) +{ + unsigned long flags; + + if (new_ldisc->num < N_TTY || new_ldisc->num >= NR_LDISCS) + return -EINVAL; + + raw_spin_lock_irqsave(&tty_ldiscs_lock, flags); + tty_ldiscs[new_ldisc->num] = new_ldisc; + raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags); + + return 0; +} +EXPORT_SYMBOL(tty_register_ldisc); + +/** + * tty_unregister_ldisc - unload a line discipline + * @ldisc: ldisc number + * + * Remove a line discipline from the kernel providing it is not currently in + * use. + * + * Locking: takes %tty_ldiscs_lock to guard against ldisc races + */ + +void tty_unregister_ldisc(struct tty_ldisc_ops *ldisc) +{ + unsigned long flags; + + raw_spin_lock_irqsave(&tty_ldiscs_lock, flags); + tty_ldiscs[ldisc->num] = NULL; + raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags); +} +EXPORT_SYMBOL(tty_unregister_ldisc); + +static struct tty_ldisc_ops *get_ldops(int disc) +{ + unsigned long flags; + struct tty_ldisc_ops *ldops, *ret; + + raw_spin_lock_irqsave(&tty_ldiscs_lock, flags); + ret = ERR_PTR(-EINVAL); + ldops = tty_ldiscs[disc]; + if (ldops) { + ret = ERR_PTR(-EAGAIN); + if (try_module_get(ldops->owner)) + ret = ldops; + } + raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags); + return ret; +} + +static void put_ldops(struct tty_ldisc_ops *ldops) +{ + unsigned long flags; + + raw_spin_lock_irqsave(&tty_ldiscs_lock, flags); + module_put(ldops->owner); + raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags); +} + +int tty_ldisc_autoload = IS_BUILTIN(CONFIG_LDISC_AUTOLOAD); + +/** + * tty_ldisc_get - take a reference to an ldisc + * @tty: tty device + * @disc: ldisc number + * + * Takes a reference to a line discipline. Deals with refcounts and module + * locking counts. If the discipline is not available, its module loaded, if + * possible. + * + * Returns: + * * -%EINVAL if the discipline index is not [%N_TTY .. %NR_LDISCS] or if the + * discipline is not registered + * * -%EAGAIN if request_module() failed to load or register the discipline + * * -%ENOMEM if allocation failure + * * Otherwise, returns a pointer to the discipline and bumps the ref count + * + * Locking: takes %tty_ldiscs_lock to guard against ldisc races + */ +static struct tty_ldisc *tty_ldisc_get(struct tty_struct *tty, 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)) { + if (!capable(CAP_SYS_MODULE) && !tty_ldisc_autoload) + return ERR_PTR(-EPERM); + request_module("tty-ldisc-%d", disc); + ldops = get_ldops(disc); + if (IS_ERR(ldops)) + return ERR_CAST(ldops); + } + + /* + * There is no way to handle allocation failure of only 16 bytes. + * Let's simplify error handling and save more memory. + */ + ld = kmalloc(sizeof(struct tty_ldisc), GFP_KERNEL | __GFP_NOFAIL); + ld->ops = ldops; + ld->tty = tty; + + return ld; +} + +/** + * tty_ldisc_put - release the ldisc + * @ld: lisdsc to release + * + * Complement of tty_ldisc_get(). + */ +static void tty_ldisc_put(struct tty_ldisc *ld) +{ + if (WARN_ON_ONCE(!ld)) + return; + + put_ldops(ld->ops); + kfree(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; +} + +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, +}; + +/** + * 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. + * + * Returns: %NULL if the tty has been hungup and not re-opened with a new file + * descriptor, otherwise valid ldisc reference + * + * Note 1: 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). + * + * Note 2: a file_operations routine (read/poll/write) should use this function + * to wait for any ldisc lifetime events to finish. + */ +struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty) +{ + struct tty_ldisc *ld; + + ldsem_down_read(&tty->ldisc_sem, MAX_SCHEDULE_TIMEOUT); + ld = tty->ldisc; + if (!ld) + ldsem_up_read(&tty->ldisc_sem); + 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. + */ +struct tty_ldisc *tty_ldisc_ref(struct tty_struct *tty) +{ + struct tty_ldisc *ld = NULL; + + if (ldsem_down_read_trylock(&tty->ldisc_sem)) { + ld = tty->ldisc; + if (!ld) + ldsem_up_read(&tty->ldisc_sem); + } + return ld; +} +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. + */ +void tty_ldisc_deref(struct tty_ldisc *ld) +{ + ldsem_up_read(&ld->tty->ldisc_sem); +} +EXPORT_SYMBOL_GPL(tty_ldisc_deref); + + +static inline int +__tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout) +{ + return ldsem_down_write(&tty->ldisc_sem, timeout); +} + +static inline int +__tty_ldisc_lock_nested(struct tty_struct *tty, unsigned long timeout) +{ + return ldsem_down_write_nested(&tty->ldisc_sem, + LDISC_SEM_OTHER, timeout); +} + +static inline void __tty_ldisc_unlock(struct tty_struct *tty) +{ + ldsem_up_write(&tty->ldisc_sem); +} + +int tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout) +{ + int ret; + + /* Kindly asking blocked readers to release the read side */ + set_bit(TTY_LDISC_CHANGING, &tty->flags); + wake_up_interruptible_all(&tty->read_wait); + wake_up_interruptible_all(&tty->write_wait); + + ret = __tty_ldisc_lock(tty, timeout); + if (!ret) + return -EBUSY; + set_bit(TTY_LDISC_HALTED, &tty->flags); + return 0; +} + +void tty_ldisc_unlock(struct tty_struct *tty) +{ + clear_bit(TTY_LDISC_HALTED, &tty->flags); + /* Can be cleared here - ldisc_unlock will wake up writers firstly */ + clear_bit(TTY_LDISC_CHANGING, &tty->flags); + __tty_ldisc_unlock(tty); +} + +static int +tty_ldisc_lock_pair_timeout(struct tty_struct *tty, struct tty_struct *tty2, + unsigned long timeout) +{ + int ret; + + if (tty < tty2) { + ret = __tty_ldisc_lock(tty, timeout); + if (ret) { + ret = __tty_ldisc_lock_nested(tty2, timeout); + if (!ret) + __tty_ldisc_unlock(tty); + } + } else { + /* if this is possible, it has lots of implications */ + WARN_ON_ONCE(tty == tty2); + if (tty2 && tty != tty2) { + ret = __tty_ldisc_lock(tty2, timeout); + if (ret) { + ret = __tty_ldisc_lock_nested(tty, timeout); + if (!ret) + __tty_ldisc_unlock(tty2); + } + } else + ret = __tty_ldisc_lock(tty, timeout); + } + + if (!ret) + return -EBUSY; + + set_bit(TTY_LDISC_HALTED, &tty->flags); + if (tty2) + set_bit(TTY_LDISC_HALTED, &tty2->flags); + return 0; +} + +static void tty_ldisc_lock_pair(struct tty_struct *tty, struct tty_struct *tty2) +{ + tty_ldisc_lock_pair_timeout(tty, tty2, MAX_SCHEDULE_TIMEOUT); +} + +static void tty_ldisc_unlock_pair(struct tty_struct *tty, + struct tty_struct *tty2) +{ + __tty_ldisc_unlock(tty); + if (tty2) + __tty_ldisc_unlock(tty2); +} + +/** + * tty_ldisc_flush - flush line discipline queue + * @tty: tty to flush ldisc for + * + * Flush the line discipline queue (if any) and the tty flip buffers for this + * @tty. + */ +void tty_ldisc_flush(struct tty_struct *tty) +{ + struct tty_ldisc *ld = tty_ldisc_ref(tty); + + tty_buffer_flush(tty, ld); + if (ld) + tty_ldisc_deref(ld); +} +EXPORT_SYMBOL_GPL(tty_ldisc_flush); + +/** + * tty_set_termios_ldisc - set ldisc field + * @tty: tty structure + * @disc: 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. + * + * The line discipline-related tty_struct fields are reset to prevent the ldisc + * driver from re-using stale information for the new ldisc instance. + * + * Locking: takes termios_rwsem + */ +static void tty_set_termios_ldisc(struct tty_struct *tty, int disc) +{ + down_write(&tty->termios_rwsem); + tty->termios.c_line = disc; + up_write(&tty->termios_rwsem); + + tty->disc_data = NULL; + tty->receive_room = 0; +} + +/** + * 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 */ + ret = ld->ops->open(tty); + if (ret) + clear_bit(TTY_LDISC_OPEN, &tty->flags); + + tty_ldisc_debug(tty, "%p: opened\n", ld); + 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) +{ + lockdep_assert_held_write(&tty->ldisc_sem); + 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_debug(tty, "%p: closed\n", ld); +} + +/** + * tty_ldisc_failto - helper for ldisc failback + * @tty: tty to open the ldisc on + * @ld: ldisc we are trying to fail back to + * + * Helper to try and recover a tty when switching back to the old ldisc fails + * and we need something attached. + */ +static int tty_ldisc_failto(struct tty_struct *tty, int ld) +{ + struct tty_ldisc *disc = tty_ldisc_get(tty, ld); + int r; + + lockdep_assert_held_write(&tty->ldisc_sem); + if (IS_ERR(disc)) + return PTR_ERR(disc); + tty->ldisc = disc; + tty_set_termios_ldisc(tty, ld); + r = tty_ldisc_open(tty, disc); + if (r < 0) + tty_ldisc_put(disc); + return r; +} + +/** + * 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) +{ + /* There is an outstanding reference here so this is safe */ + if (tty_ldisc_failto(tty, old->ops->num) < 0) { + const char *name = tty_name(tty); + + pr_warn("Falling back ldisc for %s.\n", name); + /* + * The traditional behaviour is to fall back to N_TTY, we + * want to avoid falling back to N_NULL unless we have no + * choice to avoid the risk of breaking anything + */ + if (tty_ldisc_failto(tty, N_TTY) < 0 && + tty_ldisc_failto(tty, N_NULL) < 0) + panic("Couldn't open N_NULL ldisc for %s.", name); + } +} + +/** + * tty_set_ldisc - set line discipline + * @tty: the terminal to set + * @disc: the line discipline number + * + * 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. + */ +int tty_set_ldisc(struct tty_struct *tty, int disc) +{ + int retval; + struct tty_ldisc *old_ldisc, *new_ldisc; + + new_ldisc = tty_ldisc_get(tty, disc); + if (IS_ERR(new_ldisc)) + return PTR_ERR(new_ldisc); + + tty_lock(tty); + retval = tty_ldisc_lock(tty, 5 * HZ); + if (retval) + goto err; + + if (!tty->ldisc) { + retval = -EIO; + goto out; + } + + /* Check the no-op case */ + if (tty->ldisc->ops->num == disc) + goto out; + + if (test_bit(TTY_HUPPED, &tty->flags)) { + /* We were raced by hangup */ + retval = -EIO; + goto out; + } + + old_ldisc = tty->ldisc; + + /* Shutdown the old discipline. */ + tty_ldisc_close(tty, old_ldisc); + + /* Now set up the new line discipline. */ + tty->ldisc = new_ldisc; + tty_set_termios_ldisc(tty, disc); + + 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, old_ldisc); + } + + if (tty->ldisc->ops->num != old_ldisc->ops->num && tty->ops->set_ldisc) { + down_read(&tty->termios_rwsem); + tty->ops->set_ldisc(tty); + up_read(&tty->termios_rwsem); + } + + /* + * At this point we hold a reference to the new ldisc and a + * reference to the old ldisc, or we hold two references to + * the old ldisc (if it was restored as part of error cleanup + * above). In either case, releasing a single reference from + * the old ldisc is correct. + */ + new_ldisc = old_ldisc; +out: + tty_ldisc_unlock(tty); + + /* + * Restart the work queue in case no characters kick it off. Safe if + * already running + */ + tty_buffer_restart_work(tty->port); +err: + tty_ldisc_put(new_ldisc); /* drop the extra reference */ + tty_unlock(tty); + return retval; +} +EXPORT_SYMBOL_GPL(tty_set_ldisc); + +/** + * tty_ldisc_kill - teardown ldisc + * @tty: tty being released + * + * Perform final close of the ldisc and reset @tty->ldisc + */ +static void tty_ldisc_kill(struct tty_struct *tty) +{ + lockdep_assert_held_write(&tty->ldisc_sem); + if (!tty->ldisc) + return; + /* + * 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; +} + +/** + * 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) +{ + down_write(&tty->termios_rwsem); + 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); + up_write(&tty->termios_rwsem); +} + + +/** + * tty_ldisc_reinit - reinitialise the tty ldisc + * @tty: tty to reinit + * @disc: line discipline to reinitialize + * + * Completely reinitialize the line discipline state, by closing the current + * instance, if there is one, and opening a new instance. If an error occurs + * opening the new non-%N_TTY instance, the instance is dropped and @tty->ldisc + * reset to %NULL. The caller can then retry with %N_TTY instead. + * + * Returns: 0 if successful, otherwise error code < 0 + */ +int tty_ldisc_reinit(struct tty_struct *tty, int disc) +{ + struct tty_ldisc *ld; + int retval; + + lockdep_assert_held_write(&tty->ldisc_sem); + ld = tty_ldisc_get(tty, disc); + if (IS_ERR(ld)) { + BUG_ON(disc == N_TTY); + return PTR_ERR(ld); + } + + if (tty->ldisc) { + tty_ldisc_close(tty, tty->ldisc); + tty_ldisc_put(tty->ldisc); + } + + /* switch the line discipline */ + tty->ldisc = ld; + tty_set_termios_ldisc(tty, disc); + retval = tty_ldisc_open(tty, tty->ldisc); + if (retval) { + tty_ldisc_put(tty->ldisc); + tty->ldisc = NULL; + } + return retval; +} + +/** + * tty_ldisc_hangup - hangup ldisc reset + * @tty: tty being hung up + * @reinit: whether to re-initialise the tty + * + * 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, bool reinit) +{ + struct tty_ldisc *ld; + + tty_ldisc_debug(tty, "%p: hangup\n", tty->ldisc); + + ld = tty_ldisc_ref(tty); + if (ld != NULL) { + 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); + } + + wake_up_interruptible_poll(&tty->write_wait, EPOLLOUT); + wake_up_interruptible_poll(&tty->read_wait, EPOLLIN); + + /* + * Shutdown the current line discipline, and reset it to + * N_TTY if need be. + * + * Avoid racing set_ldisc or tty_ldisc_release + */ + tty_ldisc_lock(tty, MAX_SCHEDULE_TIMEOUT); + + if (tty->driver->flags & TTY_DRIVER_RESET_TERMIOS) + tty_reset_termios(tty); + + if (tty->ldisc) { + if (reinit) { + if (tty_ldisc_reinit(tty, tty->termios.c_line) < 0 && + tty_ldisc_reinit(tty, N_TTY) < 0) + WARN_ON(tty_ldisc_reinit(tty, N_NULL) < 0); + } else + tty_ldisc_kill(tty); + } + tty_ldisc_unlock(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) +{ + int retval = tty_ldisc_open(tty, tty->ldisc); + + if (retval) + return retval; + + if (o_tty) { + /* + * Called without o_tty->ldisc_sem held, as o_tty has been + * just allocated and no one has a reference to it. + */ + retval = tty_ldisc_open(o_tty, o_tty->ldisc); + if (retval) { + tty_ldisc_close(tty, tty->ldisc); + return retval; + } + } + return 0; +} + +/** + * tty_ldisc_release - release line discipline + * @tty: tty being shut down (or one end of pty pair) + * + * Called during the final close of a tty or a pty pair in order to shut down + * the line discpline layer. On exit, each tty's ldisc is %NULL. + */ +void tty_ldisc_release(struct tty_struct *tty) +{ + struct tty_struct *o_tty = tty->link; + + /* + * Shutdown this line discipline. As this is the final close, + * it does not race with the set_ldisc code path. + */ + + tty_ldisc_lock_pair(tty, o_tty); + tty_ldisc_kill(tty); + if (o_tty) + tty_ldisc_kill(o_tty); + tty_ldisc_unlock_pair(tty, o_tty); + + /* + * And the memory resources remaining (buffers, termios) will be + * disposed of when the kref hits zero + */ + + tty_ldisc_debug(tty, "released\n"); +} + +/** + * 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. + */ +int tty_ldisc_init(struct tty_struct *tty) +{ + struct tty_ldisc *ld = tty_ldisc_get(tty, N_TTY); + + if (IS_ERR(ld)) + return PTR_ERR(ld); + tty->ldisc = ld; + return 0; +} + +/** + * tty_ldisc_deinit - ldisc cleanup for new tty + * @tty: tty that was allocated recently + * + * The tty structure must not be completely set up (tty_ldisc_setup()) when + * this call is made. + */ +void tty_ldisc_deinit(struct tty_struct *tty) +{ + /* no ldisc_sem, tty is being destroyed */ + if (tty->ldisc) + tty_ldisc_put(tty->ldisc); + tty->ldisc = NULL; +} -- cgit v1.2.3