linux/drivers/tty/tty_ldisc.c
Jiri Slaby cbb68f9199 tty: reformat kernel-doc in tty_ldisc.c
Kernel-doc is a bit strict about some formatting. So fix these:
1) When there is a tab in comments, it thinks the line is a continuation
   one. So the description of the functions end up as descriptions of
   the last parameter described. Remove the tabs.

2) Remove newlines before parameters description and after the comments.
   This was not wrong per se, only inconsistent with the rest of the
   file.

3) Add periods to the end of sentences where appropriate.

4) Add "()" to function names and "%" to constants, so that they are
   properly highlighted.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20211126081611.11001-14-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-11-26 16:27:43 +01:00

856 lines
21 KiB
C

// SPDX-License-Identifier: GPL-2.0
#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/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>
#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;
int ret = 0;
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 ret;
}
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);
}
static 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;
}
static struct ctl_table tty_table[] = {
{
.procname = "ldisc_autoload",
.data = &tty_ldisc_autoload,
.maxlen = sizeof(tty_ldisc_autoload),
.mode = 0644,
.proc_handler = proc_dointvec,
.extra1 = SYSCTL_ZERO,
.extra2 = SYSCTL_ONE,
},
{ }
};
static struct ctl_table tty_dir_table[] = {
{
.procname = "tty",
.mode = 0555,
.child = tty_table,
},
{ }
};
static struct ctl_table tty_root_table[] = {
{
.procname = "dev",
.mode = 0555,
.child = tty_dir_table,
},
{ }
};
void tty_sysctl_init(void)
{
register_sysctl_table(tty_root_table);
}