include/linux/tty.h

#ifndef _LINUX_TTY_H
#define _LINUX_TTY_H

#include <linux/fs.h>
#include <linux/major.h>
#include <linux/termios.h>
#include <linux/workqueue.h>
#include <linux/tty_driver.h>
#include <linux/tty_ldisc.h>
#include <linux/mutex.h>
#include <linux/tty_flags.h>
#include <uapi/linux/tty.h>
#include <linux/rwsem.h>
#include <linux/llist.h>



/*
 * (Note: the *_driver.minor_start values 1, 64, 128, 192 are
 * hardcoded at present.)
 */
#define NR_UNIX98_PTY_DEFAULT	4096      /* Default maximum for Unix98 ptys */
#define NR_UNIX98_PTY_RESERVE	1024	  /* Default reserve for main devpts */
#define NR_UNIX98_PTY_MAX	(1 << MINORBITS) /* Absolute limit */

/*
 * This character is the same as _POSIX_VDISABLE: it cannot be used as
 * a c_cc[] character, but indicates that a particular special character
 * isn't in use (eg VINTR has no character etc)
 */
#define __DISABLED_CHAR '\0'

struct tty_buffer {
	union {
		struct tty_buffer *next;
		struct llist_node free;
	};
	int used;
	int size;
	int commit;
	int read;
	/* Data points here */
	unsigned long data[0];
};

static inline unsigned char *char_buf_ptr(struct tty_buffer *b, int ofs)
{
	return ((unsigned char *)b->data) + ofs;
}

static inline char *flag_buf_ptr(struct tty_buffer *b, int ofs)
{
	return (char *)char_buf_ptr(b, ofs) + b->size;
}

/*
 * We default to dicing tty buffer allocations to this many characters
 * in order to avoid multiple page allocations. We know the size of
 * tty_buffer itself but it must also be taken into account that the
 * the buffer is 256 byte aligned. See tty_buffer_find for the allocation
 * logic this must match
 */

#define TTY_BUFFER_PAGE	(((PAGE_SIZE - sizeof(struct tty_buffer)) / 2) & ~0xFF)


struct tty_bufhead {
	struct work_struct work;
	spinlock_t lock;
	struct tty_buffer sentinel;
	struct tty_buffer *head;	/* Queue head */
	struct tty_buffer *tail;	/* Active buffer */
	struct llist_head free;		/* Free queue head */
	atomic_t	   memory_used; /* In-use buffers excluding free list */
};
/*
 * When a break, frame error, or parity error happens, these codes are
 * stuffed into the flags buffer.
 */
#define TTY_NORMAL	0
#define TTY_BREAK	1
#define TTY_FRAME	2
#define TTY_PARITY	3
#define TTY_OVERRUN	4

#define INTR_CHAR(tty) ((tty)->termios.c_cc[VINTR])
#define QUIT_CHAR(tty) ((tty)->termios.c_cc[VQUIT])
#define ERASE_CHAR(tty) ((tty)->termios.c_cc[VERASE])
#define KILL_CHAR(tty) ((tty)->termios.c_cc[VKILL])
#define EOF_CHAR(tty) ((tty)->termios.c_cc[VEOF])
#define TIME_CHAR(tty) ((tty)->termios.c_cc[VTIME])
#define MIN_CHAR(tty) ((tty)->termios.c_cc[VMIN])
#define SWTC_CHAR(tty) ((tty)->termios.c_cc[VSWTC])
#define START_CHAR(tty) ((tty)->termios.c_cc[VSTART])
#define STOP_CHAR(tty) ((tty)->termios.c_cc[VSTOP])
#define SUSP_CHAR(tty) ((tty)->termios.c_cc[VSUSP])
#define EOL_CHAR(tty) ((tty)->termios.c_cc[VEOL])
#define REPRINT_CHAR(tty) ((tty)->termios.c_cc[VREPRINT])
#define DISCARD_CHAR(tty) ((tty)->termios.c_cc[VDISCARD])
#define WERASE_CHAR(tty) ((tty)->termios.c_cc[VWERASE])
#define LNEXT_CHAR(tty)	((tty)->termios.c_cc[VLNEXT])
#define EOL2_CHAR(tty) ((tty)->termios.c_cc[VEOL2])

#define _I_FLAG(tty, f)	((tty)->termios.c_iflag & (f))
#define _O_FLAG(tty, f)	((tty)->termios.c_oflag & (f))
#define _C_FLAG(tty, f)	((tty)->termios.c_cflag & (f))
#define _L_FLAG(tty, f)	((tty)->termios.c_lflag & (f))

#define I_IGNBRK(tty)	_I_FLAG((tty), IGNBRK)
#define I_BRKINT(tty)	_I_FLAG((tty), BRKINT)
#define I_IGNPAR(tty)	_I_FLAG((tty), IGNPAR)
#define I_PARMRK(tty)	_I_FLAG((tty), PARMRK)
#define I_INPCK(tty)	_I_FLAG((tty), INPCK)
#define I_ISTRIP(tty)	_I_FLAG((tty), ISTRIP)
#define I_INLCR(tty)	_I_FLAG((tty), INLCR)
#define I_IGNCR(tty)	_I_FLAG((tty), IGNCR)
#define I_ICRNL(tty)	_I_FLAG((tty), ICRNL)
#define I_IUCLC(tty)	_I_FLAG((tty), IUCLC)
#define I_IXON(tty)	_I_FLAG((tty), IXON)
#define I_IXANY(tty)	_I_FLAG((tty), IXANY)
#define I_IXOFF(tty)	_I_FLAG((tty), IXOFF)
#define I_IMAXBEL(tty)	_I_FLAG((tty), IMAXBEL)
#define I_IUTF8(tty)	_I_FLAG((tty), IUTF8)

#define O_OPOST(tty)	_O_FLAG((tty), OPOST)
#define O_OLCUC(tty)	_O_FLAG((tty), OLCUC)
#define O_ONLCR(tty)	_O_FLAG((tty), ONLCR)
#define O_OCRNL(tty)	_O_FLAG((tty), OCRNL)
#define O_ONOCR(tty)	_O_FLAG((tty), ONOCR)
#define O_ONLRET(tty)	_O_FLAG((tty), ONLRET)
#define O_OFILL(tty)	_O_FLAG((tty), OFILL)
#define O_OFDEL(tty)	_O_FLAG((tty), OFDEL)
#define O_NLDLY(tty)	_O_FLAG((tty), NLDLY)
#define O_CRDLY(tty)	_O_FLAG((tty), CRDLY)
#define O_TABDLY(tty)	_O_FLAG((tty), TABDLY)
#define O_BSDLY(tty)	_O_FLAG((tty), BSDLY)
#define O_VTDLY(tty)	_O_FLAG((tty), VTDLY)
#define O_FFDLY(tty)	_O_FLAG((tty), FFDLY)

#define C_BAUD(tty)	_C_FLAG((tty), CBAUD)
#define C_CSIZE(tty)	_C_FLAG((tty), CSIZE)
#define C_CSTOPB(tty)	_C_FLAG((tty), CSTOPB)
#define C_CREAD(tty)	_C_FLAG((tty), CREAD)
#define C_PARENB(tty)	_C_FLAG((tty), PARENB)
#define C_PARODD(tty)	_C_FLAG((tty), PARODD)
#define C_HUPCL(tty)	_C_FLAG((tty), HUPCL)
#define C_CLOCAL(tty)	_C_FLAG((tty), CLOCAL)
#define C_CIBAUD(tty)	_C_FLAG((tty), CIBAUD)
#define C_CRTSCTS(tty)	_C_FLAG((tty), CRTSCTS)

#define L_ISIG(tty)	_L_FLAG((tty), ISIG)
#define L_ICANON(tty)	_L_FLAG((tty), ICANON)
#define L_XCASE(tty)	_L_FLAG((tty), XCASE)
#define L_ECHO(tty)	_L_FLAG((tty), ECHO)
#define L_ECHOE(tty)	_L_FLAG((tty), ECHOE)
#define L_ECHOK(tty)	_L_FLAG((tty), ECHOK)
#define L_ECHONL(tty)	_L_FLAG((tty), ECHONL)
#define L_NOFLSH(tty)	_L_FLAG((tty), NOFLSH)
#define L_TOSTOP(tty)	_L_FLAG((tty), TOSTOP)
#define L_ECHOCTL(tty)	_L_FLAG((tty), ECHOCTL)
#define L_ECHOPRT(tty)	_L_FLAG((tty), ECHOPRT)
#define L_ECHOKE(tty)	_L_FLAG((tty), ECHOKE)
#define L_FLUSHO(tty)	_L_FLAG((tty), FLUSHO)
#define L_PENDIN(tty)	_L_FLAG((tty), PENDIN)
#define L_IEXTEN(tty)	_L_FLAG((tty), IEXTEN)
#define L_EXTPROC(tty)	_L_FLAG((tty), EXTPROC)

struct device;
struct signal_struct;

/*
 * Port level information. Each device keeps its own port level information
 * so provide a common structure for those ports wanting to use common support
 * routines.
 *
 * The tty port has a different lifetime to the tty so must be kept apart.
 * In addition be careful as tty -> port mappings are valid for the life
 * of the tty object but in many cases port -> tty mappings are valid only
 * until a hangup so don't use the wrong path.
 */

struct tty_port;

struct tty_port_operations {
	/* Return 1 if the carrier is raised */
	int (*carrier_raised)(struct tty_port *port);
	/* Control the DTR line */
	void (*dtr_rts)(struct tty_port *port, int raise);
	/* Called when the last close completes or a hangup finishes
	   IFF the port was initialized. Do not use to free resources. Called
	   under the port mutex to serialize against activate/shutdowns */
	void (*shutdown)(struct tty_port *port);
	void (*drop)(struct tty_port *port);
	/* Called under the port mutex from tty_port_open, serialized using
	   the port mutex */
        /* FIXME: long term getting the tty argument *out* of this would be
           good for consoles */
	int (*activate)(struct tty_port *port, struct tty_struct *tty);
	/* Called on the final put of a port */
	void (*destruct)(struct tty_port *port);
};
	
struct tty_port {
	struct tty_bufhead	buf;		/* Locked internally */
	struct tty_struct	*tty;		/* Back pointer */
	struct tty_struct	*itty;		/* internal back ptr */
	const struct tty_port_operations *ops;	/* Port operations */
	spinlock_t		lock;		/* Lock protecting tty field */
	int			blocked_open;	/* Waiting to open */
	int			count;		/* Usage count */
	wait_queue_head_t	open_wait;	/* Open waiters */
	wait_queue_head_t	close_wait;	/* Close waiters */
	wait_queue_head_t	delta_msr_wait;	/* Modem status change */
	unsigned long		flags;		/* TTY flags ASY_*/
	unsigned long		iflags;		/* TTYP_ internal flags */
#define TTYP_FLUSHING			1  /* Flushing to ldisc in progress */
#define TTYP_FLUSHPENDING		2  /* Queued buffer flush pending */
	unsigned char		console:1,	/* port is a console */
				low_latency:1;	/* direct buffer flush */
	struct mutex		mutex;		/* Locking */
	struct mutex		buf_mutex;	/* Buffer alloc lock */
	unsigned char		*xmit_buf;	/* Optional buffer */
	unsigned int		close_delay;	/* Close port delay */
	unsigned int		closing_wait;	/* Delay for output */
	int			drain_delay;	/* Set to zero if no pure time
						   based drain is needed else
						   set to size of fifo */
	struct kref		kref;		/* Ref counter */
};

/*
 * Where all of the state associated with a tty is kept while the tty
 * is open.  Since the termios state should be kept even if the tty
 * has been closed --- for things like the baud rate, etc --- it is
 * not stored here, but rather a pointer to the real state is stored
 * here.  Possible the winsize structure should have the same
 * treatment, but (1) the default 80x24 is usually right and (2) it's
 * most often used by a windowing system, which will set the correct
 * size each time the window is created or resized anyway.
 * 						- TYT, 9/14/92
 */

struct tty_operations;

struct tty_struct {
	int	magic;
	struct kref kref;
	struct device *dev;
	struct tty_driver *driver;
	const struct tty_operations *ops;
	int index;

	/* Protects ldisc changes: Lock tty not pty */
	struct ld_semaphore ldisc_sem;
	struct tty_ldisc *ldisc;

	struct mutex atomic_write_lock;
	struct mutex legacy_mutex;
	struct mutex throttle_mutex;
	struct rw_semaphore termios_rwsem;
	spinlock_t ctrl_lock;
	/* Termios values are protected by the termios rwsem */
	struct ktermios termios, termios_locked;
	struct termiox *termiox;	/* May be NULL for unsupported */
	char name[64];
	struct pid *pgrp;		/* Protected by ctrl lock */
	struct pid *session;
	unsigned long flags;
	int count;
	struct winsize winsize;		/* termios rwsem */
	unsigned char stopped:1, hw_stopped:1, flow_stopped:1, packet:1;
	unsigned char ctrl_status;	/* ctrl_lock */
	unsigned int receive_room;	/* Bytes free for queue */
	int flow_change;

	struct tty_struct *link;
	struct fasync_struct *fasync;
	int alt_speed;		/* For magic substitution of 38400 bps */
	wait_queue_head_t write_wait;
	wait_queue_head_t read_wait;
	struct work_struct hangup_work;
	void *disc_data;
	void *driver_data;
	struct list_head tty_files;

#define N_TTY_BUF_SIZE 4096

	unsigned char closing:1;
	unsigned char *write_buf;
	int write_cnt;
	/* If the tty has a pending do_SAK, queue it here - akpm */
	struct work_struct SAK_work;
	struct tty_port *port;
};

/* Each of a tty's open files has private_data pointing to tty_file_private */
struct tty_file_private {
	struct tty_struct *tty;
	struct file *file;
	struct list_head list;
};

/* tty magic number */
#define TTY_MAGIC		0x5401

/*
 * These bits are used in the flags field of the tty structure.
 *
 * So that interrupts won't be able to mess up the queues,
 * copy_to_cooked must be atomic with respect to itself, as must
 * tty->write.  Thus, you must use the inline functions set_bit() and
 * clear_bit() to make things atomic.
 */
#define TTY_THROTTLED 		0	/* Call unthrottle() at threshold min */
#define TTY_IO_ERROR 		1	/* Cause an I/O error (may be no ldisc too) */
#define TTY_OTHER_CLOSED 	2	/* Other side (if any) has closed */
#define TTY_EXCLUSIVE 		3	/* Exclusive open mode */
#define TTY_DEBUG 		4	/* Debugging */
#define TTY_DO_WRITE_WAKEUP 	5	/* Call write_wakeup after queuing new */
#define TTY_PUSH 		6	/* n_tty private */
#define TTY_CLOSING 		7	/* ->close() in progress */
#define TTY_LDISC_OPEN	 	11	/* Line discipline is open */
#define TTY_PTY_LOCK 		16	/* pty private */
#define TTY_NO_WRITE_SPLIT 	17	/* Preserve write boundaries to driver */
#define TTY_HUPPED 		18	/* Post driver->hangup() */
#define TTY_HUPPING 		21	/* ->hangup() in progress */
#define TTY_LDISC_HALTED	22	/* Line discipline is halted */

#define TTY_WRITE_FLUSH(tty) tty_write_flush((tty))

/* Values for tty->flow_change */
#define TTY_THROTTLE_SAFE 1
#define TTY_UNTHROTTLE_SAFE 2

static inline void __tty_set_flow_change(struct tty_struct *tty, int val)
{
	tty->flow_change = val;
}

static inline void tty_set_flow_change(struct tty_struct *tty, int val)
{
	tty->flow_change = val;
	smp_mb();
}

#ifdef CONFIG_TTY
extern void console_init(void);
extern void tty_kref_put(struct tty_struct *tty);
extern struct pid *tty_get_pgrp(struct tty_struct *tty);
extern void tty_vhangup_self(void);
extern void disassociate_ctty(int priv);
extern dev_t tty_devnum(struct tty_struct *tty);
extern void proc_clear_tty(struct task_struct *p);
extern struct tty_struct *get_current_tty(void);
/* tty_io.c */
extern int __init tty_init(void);
#else
static inline void console_init(void)
{ }
static inline void tty_kref_put(struct tty_struct *tty)
{ }
static inline struct pid *tty_get_pgrp(struct tty_struct *tty)
{ return NULL; }
static inline void tty_vhangup_self(void)
{ }
static inline void disassociate_ctty(int priv)
{ }
static inline dev_t tty_devnum(struct tty_struct *tty)
{ return 0; }
static inline void proc_clear_tty(struct task_struct *p)
{ }
static inline struct tty_struct *get_current_tty(void)
{ return NULL; }
/* tty_io.c */
static inline int __init tty_init(void)
{ return 0; }
#endif

extern void tty_write_flush(struct tty_struct *);

extern struct ktermios tty_std_termios;

extern int vcs_init(void);

extern struct class *tty_class;

/**
 *	tty_kref_get		-	get a tty reference
 *	@tty: tty device
 *
 *	Return a new reference to a tty object. The caller must hold
 *	sufficient locks/counts to ensure that their existing reference cannot
 *	go away
 */

static inline struct tty_struct *tty_kref_get(struct tty_struct *tty)
{
	if (tty)
		kref_get(&tty->kref);
	return tty;
}

extern int tty_paranoia_check(struct tty_struct *tty, struct inode *inode,
			      const char *routine);
extern char *tty_name(struct tty_struct *tty, char *buf);
extern void tty_wait_until_sent(struct tty_struct *tty, long timeout);
extern int tty_check_change(struct tty_struct *tty);
extern void stop_tty(struct tty_struct *tty);
extern void start_tty(struct tty_struct *tty);
extern int tty_register_driver(struct tty_driver *driver);
extern int tty_unregister_driver(struct tty_driver *driver);
extern struct device *tty_register_device(struct tty_driver *driver,
					  unsigned index, struct device *dev);
extern struct device *tty_register_device_attr(struct tty_driver *driver,
				unsigned index, struct device *device,
				void *drvdata,
				const struct attribute_group **attr_grp);
extern void tty_unregister_device(struct tty_driver *driver, unsigned index);
extern int tty_read_raw_data(struct tty_struct *tty, unsigned char *bufp,
			     int buflen);
extern void tty_write_message(struct tty_struct *tty, char *msg);
extern int tty_put_char(struct tty_struct *tty, unsigned char c);
extern int tty_chars_in_buffer(struct tty_struct *tty);
extern int tty_write_room(struct tty_struct *tty);
extern void tty_driver_flush_buffer(struct tty_struct *tty);
extern void tty_throttle(struct tty_struct *tty);
extern void tty_unthrottle(struct tty_struct *tty);
extern int tty_throttle_safe(struct tty_struct *tty);
extern int tty_unthrottle_safe(struct tty_struct *tty);
extern int tty_do_resize(struct tty_struct *tty, struct winsize *ws);
extern void tty_driver_remove_tty(struct tty_driver *driver,
				  struct tty_struct *tty);
extern void tty_free_termios(struct tty_struct *tty);
extern int is_current_pgrp_orphaned(void);
extern int is_ignored(int sig);
extern int tty_signal(int sig, struct tty_struct *tty);
extern void tty_hangup(struct tty_struct *tty);
extern void tty_vhangup(struct tty_struct *tty);
extern void tty_vhangup_locked(struct tty_struct *tty);
extern void tty_unhangup(struct file *filp);
extern int tty_hung_up_p(struct file *filp);
extern void do_SAK(struct tty_struct *tty);
extern void __do_SAK(struct tty_struct *tty);
extern void no_tty(void);
extern void tty_flush_to_ldisc(struct tty_struct *tty);
extern void tty_buffer_free_all(struct tty_port *port);
extern void tty_buffer_flush(struct tty_struct *tty);
extern void tty_buffer_init(struct tty_port *port);
extern speed_t tty_termios_baud_rate(struct ktermios *termios);
extern speed_t tty_termios_input_baud_rate(struct ktermios *termios);
extern void tty_termios_encode_baud_rate(struct ktermios *termios,
						speed_t ibaud, speed_t obaud);
extern void tty_encode_baud_rate(struct tty_struct *tty,
						speed_t ibaud, speed_t obaud);

/**
 *	tty_get_baud_rate	-	get tty bit rates
 *	@tty: tty to query
 *
 *	Returns the baud rate as an integer for this terminal. The
 *	termios lock must be held by the caller and the terminal bit
 *	flags may be updated.
 *
 *	Locking: none
 */
static inline speed_t tty_get_baud_rate(struct tty_struct *tty)
{
	return tty_termios_baud_rate(&tty->termios);
}

extern void tty_termios_copy_hw(struct ktermios *new, struct ktermios *old);
extern int tty_termios_hw_change(struct ktermios *a, struct ktermios *b);
extern int tty_set_termios(struct tty_struct *tty, struct ktermios *kt);

extern struct tty_ldisc *tty_ldisc_ref(struct tty_struct *);
extern void tty_ldisc_deref(struct tty_ldisc *);
extern struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *);
extern void tty_ldisc_hangup(struct tty_struct *tty);
extern const struct file_operations tty_ldiscs_proc_fops;

extern void tty_wakeup(struct tty_struct *tty);
extern void tty_ldisc_flush(struct tty_struct *tty);

extern long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg);
extern int tty_mode_ioctl(struct tty_struct *tty, struct file *file,
			unsigned int cmd, unsigned long arg);
extern int tty_perform_flush(struct tty_struct *tty, unsigned long arg);
extern void tty_default_fops(struct file_operations *fops);
extern struct tty_struct *alloc_tty_struct(void);
extern int tty_alloc_file(struct file *file);
extern void tty_add_file(struct tty_struct *tty, struct file *file);
extern void tty_free_file(struct file *file);
extern void free_tty_struct(struct tty_struct *tty);
extern void initialize_tty_struct(struct tty_struct *tty,
		struct tty_driver *driver, int idx);
extern void deinitialize_tty_struct(struct tty_struct *tty);
extern struct tty_struct *tty_init_dev(struct tty_driver *driver, int idx);
extern int tty_release(struct inode *inode, struct file *filp);
extern int tty_init_termios(struct tty_struct *tty);
extern int tty_standard_install(struct tty_driver *driver,
		struct tty_struct *tty);

extern struct tty_struct *tty_pair_get_tty(struct tty_struct *tty);
extern struct tty_struct *tty_pair_get_pty(struct tty_struct *tty);

extern struct mutex tty_mutex;
extern spinlock_t tty_files_lock;

extern void tty_write_unlock(struct tty_struct *tty);
extern int tty_write_lock(struct tty_struct *tty, int ndelay);
#define tty_is_writelocked(tty)  (mutex_is_locked(&tty->atomic_write_lock))

extern void tty_port_init(struct tty_port *port);
extern void tty_port_link_device(struct tty_port *port,
		struct tty_driver *driver, unsigned index);
extern struct device *tty_port_register_device(struct tty_port *port,
		struct tty_driver *driver, unsigned index,
		struct device *device);
extern struct device *tty_port_register_device_attr(struct tty_port *port,
		struct tty_driver *driver, unsigned index,
		struct device *device, void *drvdata,
		const struct attribute_group **attr_grp);
extern int tty_port_alloc_xmit_buf(struct tty_port *port);
extern void tty_port_free_xmit_buf(struct tty_port *port);
extern void tty_port_destroy(struct tty_port *port);
extern void tty_port_put(struct tty_port *port);

static inline struct tty_port *tty_port_get(struct tty_port *port)
{
	if (port)
		kref_get(&port->kref);
	return port;
}

/* If the cts flow control is enabled, return true. */
static inline bool tty_port_cts_enabled(struct tty_port *port)
{
	return port->flags & ASYNC_CTS_FLOW;
}

extern struct tty_struct *tty_port_tty_get(struct tty_port *port);
extern void tty_port_tty_set(struct tty_port *port, struct tty_struct *tty);
extern int tty_port_carrier_raised(struct tty_port *port);
extern void tty_port_raise_dtr_rts(struct tty_port *port);
extern void tty_port_lower_dtr_rts(struct tty_port *port);
extern void tty_port_hangup(struct tty_port *port);
extern void tty_port_tty_hangup(struct tty_port *port, bool check_clocal);
extern void tty_port_tty_wakeup(struct tty_port *port);
extern int tty_port_block_til_ready(struct tty_port *port,
				struct tty_struct *tty, struct file *filp);
extern int tty_port_close_start(struct tty_port *port,
				struct tty_struct *tty, struct file *filp);
extern void tty_port_close_end(struct tty_port *port, struct tty_struct *tty);
extern void tty_port_close(struct tty_port *port,
				struct tty_struct *tty, struct file *filp);
extern int tty_port_install(struct tty_port *port, struct tty_driver *driver,
				struct tty_struct *tty);
extern int tty_port_open(struct tty_port *port,
				struct tty_struct *tty, struct file *filp);
static inline int tty_port_users(struct tty_port *port)
{
	return port->count + port->blocked_open;
}

extern int tty_register_ldisc(int disc, struct tty_ldisc_ops *new_ldisc);
extern int tty_unregister_ldisc(int disc);
extern int tty_set_ldisc(struct tty_struct *tty, int ldisc);
extern int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty);
extern void tty_ldisc_release(struct tty_struct *tty, struct tty_struct *o_tty);
extern void tty_ldisc_init(struct tty_struct *tty);
extern void tty_ldisc_deinit(struct tty_struct *tty);
extern void tty_ldisc_begin(void);

static inline int tty_ldisc_receive_buf(struct tty_ldisc *ld, unsigned char *p,
					char *f, int count)
{
	if (ld->ops->receive_buf2)
		count = ld->ops->receive_buf2(ld->tty, p, f, count);
	else {
		count = min_t(int, count, ld->tty->receive_room);
		if (count)
			ld->ops->receive_buf(ld->tty, p, f, count);
	}
	return count;
}


/* n_tty.c */
extern struct tty_ldisc_ops tty_ldisc_N_TTY;
extern void n_tty_inherit_ops(struct tty_ldisc_ops *ops);

/* tty_audit.c */
#ifdef CONFIG_AUDIT
extern void tty_audit_add_data(struct tty_struct *tty, unsigned char *data,
			       size_t size, unsigned icanon);
extern void tty_audit_exit(void);
extern void tty_audit_fork(struct signal_struct *sig);
extern void tty_audit_tiocsti(struct tty_struct *tty, char ch);
extern void tty_audit_push(struct tty_struct *tty);
extern int tty_audit_push_current(void);
#else
static inline void tty_audit_add_data(struct tty_struct *tty,
		unsigned char *data, size_t size, unsigned icanon)
{
}
static inline void tty_audit_tiocsti(struct tty_struct *tty, char ch)
{
}
static inline void tty_audit_exit(void)
{
}
static inline void tty_audit_fork(struct signal_struct *sig)
{
}
static inline void tty_audit_push(struct tty_struct *tty)
{
}
static inline int tty_audit_push_current(void)
{
	return 0;
}
#endif

/* tty_ioctl.c */
extern int n_tty_ioctl_helper(struct tty_struct *tty, struct file *file,
		       unsigned int cmd, unsigned long arg);
extern long n_tty_compat_ioctl_helper(struct tty_struct *tty, struct file *file,
		       unsigned int cmd, unsigned long arg);

/* serial.c */

extern void serial_console_init(void);

/* pcxx.c */

extern int pcxe_open(struct tty_struct *tty, struct file *filp);

/* vt.c */

extern int vt_ioctl(struct tty_struct *tty,
		    unsigned int cmd, unsigned long arg);

extern long vt_compat_ioctl(struct tty_struct *tty,
		     unsigned int cmd, unsigned long arg);

/* tty_mutex.c */
/* functions for preparation of BKL removal */
extern void __lockfunc tty_lock(struct tty_struct *tty);
extern void __lockfunc tty_unlock(struct tty_struct *tty);
extern void __lockfunc tty_lock_pair(struct tty_struct *tty,
				struct tty_struct *tty2);
extern void __lockfunc tty_unlock_pair(struct tty_struct *tty,
				struct tty_struct *tty2);

/*
 * this shall be called only from where BTM is held (like close)
 *
 * We need this to ensure nobody waits for us to finish while we are waiting.
 * Without this we were encountering system stalls.
 *
 * This should be indeed removed with BTM removal later.
 *
 * Locking: BTM required. Nobody is allowed to hold port->mutex.
 */
static inline void tty_wait_until_sent_from_close(struct tty_struct *tty,
		long timeout)
{
	tty_unlock(tty); /* tty->ops->close holds the BTM, drop it while waiting */
	tty_wait_until_sent(tty, timeout);
	tty_lock(tty);
}

/*
 * wait_event_interruptible_tty -- wait for a condition with the tty lock held
 *
 * The condition we are waiting for might take a long time to
 * become true, or might depend on another thread taking the
 * BTM. In either case, we need to drop the BTM to guarantee
 * forward progress. This is a leftover from the conversion
 * from the BKL and should eventually get removed as the BTM
 * falls out of use.
 *
 * Do not use in new code.
 */
#define wait_event_interruptible_tty(tty, wq, condition)		\
({									\
	int __ret = 0;							\
	if (!(condition)) {						\
		__wait_event_interruptible_tty(tty, wq, condition, __ret);	\
	}								\
	__ret;								\
})

#define __wait_event_interruptible_tty(tty, wq, condition, ret)		\
do {									\
	DEFINE_WAIT(__wait);						\
									\
	for (;;) {							\
		prepare_to_wait(&wq, &__wait, TASK_INTERRUPTIBLE);	\
		if (condition)						\
			break;						\
		if (!signal_pending(current)) {				\
			tty_unlock(tty);					\
			schedule();					\
			tty_lock(tty);					\
			continue;					\
		}							\
		ret = -ERESTARTSYS;					\
		break;							\
	}								\
	finish_wait(&wq, &__wait);					\
} while (0)

#ifdef CONFIG_PROC_FS
extern void proc_tty_register_driver(struct tty_driver *);
extern void proc_tty_unregister_driver(struct tty_driver *);
#else
static inline void proc_tty_register_driver(struct tty_driver *d) {}
static inline void proc_tty_unregister_driver(struct tty_driver *d) {}
#endif

#endif