zte's code,first commit
Change-Id: I9a04da59e459a9bc0d67f101f700d9d7dc8d681b
diff --git a/ap/os/linux/linux-3.4.x/drivers/tty/tty_ldisc.c b/ap/os/linux/linux-3.4.x/drivers/tty/tty_ldisc.c
new file mode 100644
index 0000000..c191502
--- /dev/null
+++ b/ap/os/linux/linux-3.4.x/drivers/tty/tty_ldisc.c
@@ -0,0 +1,975 @@
+#include <linux/types.h>
+#include <linux/errno.h>
+#include <linux/kmod.h>
+#include <linux/sched.h>
+#include <linux/interrupt.h>
+#include <linux/tty.h>
+#include <linux/tty_driver.h>
+#include <linux/file.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/seq_file.h>
+#include <linux/uaccess.h>
+#include <linux/ratelimit.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);
+static DECLARE_WAIT_QUEUE_HEAD(tty_ldisc_idle);
+/* 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_nort(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_nort(flags);
+ wake_up(&tty_ldisc_idle);
+}
+
+/**
+ * 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->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);
+ 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_work_sync(&tty->buf.work);
+}
+
+/**
+ * tty_ldisc_flush_works - flush all works of a tty
+ * @tty: tty device to flush works for
+ *
+ * Sync flush all works belonging to @tty.
+ */
+static void tty_ldisc_flush_works(struct tty_struct *tty)
+{
+ flush_work_sync(&tty->hangup_work);
+ flush_work_sync(&tty->SAK_work);
+ flush_work_sync(&tty->buf.work);
+}
+
+/**
+ * tty_ldisc_wait_idle - wait for the ldisc to become idle
+ * @tty: tty to wait for
+ * @timeout: for how long to wait at most
+ *
+ * Wait for the line discipline to become idle. The discipline must
+ * have been halted for this to guarantee it remains idle.
+ */
+static int tty_ldisc_wait_idle(struct tty_struct *tty, long timeout)
+{
+ long ret;
+ ret = wait_event_timeout(tty_ldisc_idle,
+ atomic_read(&tty->ldisc->users) == 1, timeout);
+ return ret > 0 ? 0 : -EBUSY;
+}
+
+/**
+ * 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);
+
+ tty_ldisc_flush_works(tty);
+
+ retval = tty_ldisc_wait_idle(tty, 5 * HZ);
+
+ tty_lock();
+ mutex_lock(&tty->ldisc_mutex);
+
+ /* handle wait idle failure locked */
+ if (retval) {
+ tty_ldisc_put(new_ldisc);
+ goto enable;
+ }
+
+ 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);
+
+enable:
+ /*
+ * 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_work(&tty->buf.work);
+ if (o_work)
+ schedule_work(&o_tty->buf.work);
+ 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 int tty_ldisc_reinit(struct tty_struct *tty, int ldisc)
+{
+ struct tty_ldisc *ld = tty_ldisc_get(ldisc);
+
+ if (IS_ERR(ld))
+ return -1;
+
+ tty_ldisc_close(tty, tty->ldisc);
+ tty_ldisc_put(tty->ldisc);
+ tty->ldisc = NULL;
+ /*
+ * Switch the line discipline back
+ */
+ tty_ldisc_assign(tty, ld);
+ tty_set_termios_ldisc(tty, ldisc);
+
+ return 0;
+}
+
+/**
+ * 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_work_sync, which may
+ * need to wait for another function taking the BTM
+ */
+ clear_bit(TTY_LDISC, &tty->flags);
+ tty_unlock();
+ cancel_work_sync(&tty->buf.work);
+ mutex_unlock(&tty->ldisc_mutex);
+retry:
+ 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 (atomic_read(&tty->ldisc->users) != 1) {
+ char cur_n[TASK_COMM_LEN], tty_n[64];
+ long timeout = 3 * HZ;
+ tty_unlock();
+
+ while (tty_ldisc_wait_idle(tty, timeout) == -EBUSY) {
+ timeout = MAX_SCHEDULE_TIMEOUT;
+ printk_ratelimited(KERN_WARNING
+ "%s: waiting (%s) for %s took too long, but we keep waiting...\n",
+ __func__, get_task_comm(cur_n, current),
+ tty_name(tty, tty_n));
+ }
+ mutex_unlock(&tty->ldisc_mutex);
+ goto retry;
+ }
+
+ if (reset == 0) {
+
+ if (!tty_ldisc_reinit(tty, tty->termios->c_line))
+ err = tty_ldisc_open(tty, tty->ldisc);
+ else
+ err = 1;
+ }
+ /* If the re-open fails or we reset then go to N_TTY. The
+ N_TTY open cannot fail */
+ if (reset || err) {
+ BUG_ON(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);
+ tty_ldisc_flush_works(tty);
+ 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);
+}
+
+/**
+ * tty_ldisc_init - ldisc cleanup for new tty
+ * @tty: tty that was allocated recently
+ *
+ * The tty structure must not becompletely set up (tty_ldisc_setup) when
+ * this call is made.
+ */
+void tty_ldisc_deinit(struct tty_struct *tty)
+{
+ put_ldisc(tty->ldisc);
+ tty_ldisc_assign(tty, NULL);
+}
+
+void tty_ldisc_begin(void)
+{
+ /* Setup the default TTY line discipline. */
+ (void) tty_register_ldisc(N_TTY, &tty_ldisc_N_TTY);
+}