text: #ifndef _LINUX_TTY_H
  #define _LINUX_TTY_H
  
  /*
   * 'tty.h' defines some structures used by tty_io.c and some defines.
   */
  
  /*
   * These constants are also useful for user-level apps (e.g., VC
   * resizing).
   */
  #define MIN_NR_CONSOLES 1       /* must be at least 1 */
  #define MAX_NR_CONSOLES	63	/* serial lines start at 64 */
  #define MAX_NR_USER_CONSOLES 63	/* must be root to allocate above this */
  		/* Note: the ioctl VT_GETSTATE does not work for
  		   consoles 16 and higher (since it returns a short) */
  
  #ifdef __KERNEL__
  #include <linux/config.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 <asm/system.h>
  
  
  /*
   * Note: don't mess with NR_PTYS until you understand the tty minor 
   * number allocation game...
   * (Note: the *_driver.minor_start values 1, 64, 128, 192 are
   * hardcoded at present.)
   */
  #define NR_PTYS		256	/* ptys/major */
  #define NR_LDISCS	16
  
  /*
   * Unix98 PTY's can be defined as any multiple of NR_PTYS up to
   * UNIX98_PTY_MAJOR_COUNT; this section defines what we need from the
   * config options
   */
  #ifdef CONFIG_UNIX98_PTYS
  # define UNIX98_NR_MAJORS ((CONFIG_UNIX98_PTY_COUNT+NR_PTYS-1)/NR_PTYS)
  # if UNIX98_NR_MAJORS <= 0
  #  undef CONFIG_UNIX98_PTYS
  # elif UNIX98_NR_MAJORS > UNIX98_PTY_MAJOR_COUNT
  #  error  Too many Unix98 ptys defined
  #  undef  UNIX98_NR_MAJORS
  #  define UNIX98_NR_MAJORS UNIX98_PTY_MAJOR_COUNT
  # endif
  #endif
  
  /*
   * These are set up by the setup-routine at boot-time:
   */
  
  struct screen_info {
  	u8  orig_x;		/* 0x00 */
  	u8  orig_y;		/* 0x01 */
  	u16 dontuse1;		/* 0x02 -- EXT_MEM_K sits here */
  	u16 orig_video_page;	/* 0x04 */
  	u8  orig_video_mode;	/* 0x06 */
  	u8  orig_video_cols;	/* 0x07 */
  	u16 unused2;		/* 0x08 */
  	u16 orig_video_ega_bx;	/* 0x0a */
  	u16 unused3;		/* 0x0c */
  	u8  orig_video_lines;	/* 0x0e */
  	u8  orig_video_isVGA;	/* 0x0f */
  	u16 orig_video_points;	/* 0x10 */
  
  	/* VESA graphic mode -- linear frame buffer */
  	u16 lfb_width;		/* 0x12 */
  	u16 lfb_height;		/* 0x14 */
  	u16 lfb_depth;		/* 0x16 */
  	u32 lfb_base;		/* 0x18 */
  	u32 lfb_size;		/* 0x1c */
  	u16 dontuse2, dontuse3;	/* 0x20 -- CL_MAGIC and CL_OFFSET here */
  	u16 lfb_linelength;	/* 0x24 */
  	u8  red_size;		/* 0x26 */
  	u8  red_pos;		/* 0x27 */
  	u8  green_size;		/* 0x28 */
  	u8  green_pos;		/* 0x29 */
  	u8  blue_size;		/* 0x2a */
  	u8  blue_pos;		/* 0x2b */
  	u8  rsvd_size;		/* 0x2c */
  	u8  rsvd_pos;		/* 0x2d */
  	u16 vesapm_seg;		/* 0x2e */
  	u16 vesapm_off;		/* 0x30 */
  	u16 pages;		/* 0x32 */
  	u16 vesa_attributes;	/* 0x34 */
  				/* 0x36 -- 0x3f reserved for future expansion */
  };
  
  extern struct screen_info screen_info;
  
  #define ORIG_X			(screen_info.orig_x)
  #define ORIG_Y			(screen_info.orig_y)
  #define ORIG_VIDEO_MODE		(screen_info.orig_video_mode)
  #define ORIG_VIDEO_COLS 	(screen_info.orig_video_cols)
  #define ORIG_VIDEO_EGA_BX	(screen_info.orig_video_ega_bx)
  #define ORIG_VIDEO_LINES	(screen_info.orig_video_lines)
  #define ORIG_VIDEO_ISVGA	(screen_info.orig_video_isVGA)
  #define ORIG_VIDEO_POINTS       (screen_info.orig_video_points)
  
  #define VIDEO_TYPE_MDA		0x10	/* Monochrome Text Display	*/
  #define VIDEO_TYPE_CGA		0x11	/* CGA Display 			*/
  #define VIDEO_TYPE_EGAM		0x20	/* EGA/VGA in Monochrome Mode	*/
  #define VIDEO_TYPE_EGAC		0x21	/* EGA in Color Mode		*/
  #define VIDEO_TYPE_VGAC		0x22	/* VGA+ in Color Mode		*/
  #define VIDEO_TYPE_VLFB		0x23	/* VESA VGA in graphic mode	*/
  
  #define VIDEO_TYPE_PICA_S3	0x30	/* ACER PICA-61 local S3 video	*/
  #define VIDEO_TYPE_MIPS_G364	0x31    /* MIPS Magnum 4000 G364 video  */
  #define VIDEO_TYPE_SNI_RM	0x32    /* SNI RM200 PCI video          */
  #define VIDEO_TYPE_SGI          0x33    /* Various SGI graphics hardware */
  
  #define VIDEO_TYPE_TGAC		0x40	/* DEC TGA */
  
  #define VIDEO_TYPE_SUN          0x50    /* Sun frame buffer. */
  #define VIDEO_TYPE_SUNPCI       0x51    /* Sun PCI based frame buffer. */
  
  #define VIDEO_TYPE_PMAC		0x60	/* PowerMacintosh frame buffer. */
  
  /*
   * 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'
  
  /*
   * This is the flip buffer used for the tty driver.  The buffer is
   * located in the tty structure, and is used as a high speed interface
   * between the tty driver and the tty line discipline.
   */
  #define TTY_FLIPBUF_SIZE 512
  
  struct tty_flip_buffer {
  	struct work_struct		work;
  	struct semaphore pty_sem;
  	char		*char_buf_ptr;
  	unsigned char	*flag_buf_ptr;
  	int		count;
  	int		buf_num;
  	unsigned char	char_buf[2*TTY_FLIPBUF_SIZE];
  	char		flag_buf[2*TTY_FLIPBUF_SIZE];
  	unsigned char	slop[4]; /* N.B. bug overwrites buffer by 1 */
  };
  /*
   * The pty uses char_buf and flag_buf as a contiguous buffer
   */
  #define PTY_BUF_SIZE	4*TTY_FLIPBUF_SIZE
  
  /*
   * 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 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)
  
  struct device;
  /*
   * 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_struct {
  	int	magic;
  	struct tty_driver *driver;
  	int index;
  	struct tty_ldisc ldisc;
  	struct termios *termios, *termios_locked;
  	char name[64];
  	int pgrp;
  	int session;
  	unsigned long flags;
  	int count;
  	struct winsize winsize;
  	unsigned char stopped:1, hw_stopped:1, flow_stopped:1, packet:1;
  	unsigned char low_latency:1, warned:1;
  	unsigned char ctrl_status;
  
  	struct tty_struct *link;
  	struct fasync_struct *fasync;
  	struct tty_flip_buffer flip;
  	int max_flip_cnt;
  	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
  	
  	/*
  	 * The following is data for the N_TTY line discipline.  For
  	 * historical reasons, this is included in the tty structure.
  	 */
  	unsigned int column;
  	unsigned char lnext:1, erasing:1, raw:1, real_raw:1, icanon:1;
  	unsigned char closing:1;
  	unsigned short minimum_to_wake;
  	unsigned long overrun_time;
  	int num_overrun;
  	unsigned long process_char_map[256/(8*sizeof(unsigned long))];
  	char *read_buf;
  	int read_head;
  	int read_tail;
  	int read_cnt;
  	unsigned long read_flags[N_TTY_BUF_SIZE/(8*sizeof(unsigned long))];
  	int canon_data;
  	unsigned long canon_head;
  	unsigned int canon_column;
  	struct semaphore atomic_read;
  	struct semaphore atomic_write;
  	spinlock_t read_lock;
  	/* If the tty has a pending do_SAK, queue it here - akpm */
  	struct work_struct SAK_work;
  };
  
  /* 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
  #define TTY_IO_ERROR 1
  #define TTY_OTHER_CLOSED 2
  #define TTY_EXCLUSIVE 3
  #define TTY_DEBUG 4
  #define TTY_DO_WRITE_WAKEUP 5
  #define TTY_PUSH 6
  #define TTY_CLOSING 7
  #define TTY_DONT_FLIP 8
  #define TTY_HW_COOK_OUT 14
  #define TTY_HW_COOK_IN 15
  #define TTY_PTY_LOCK 16
  #define TTY_NO_WRITE_SPLIT 17
  
  #define TTY_WRITE_FLUSH(tty) tty_write_flush((tty))
  
  extern void tty_write_flush(struct tty_struct *);
  
  extern struct termios tty_std_termios;
  extern struct tty_ldisc ldiscs[];
  extern int fg_console, last_console, want_console;
  
  extern int kmsg_redirect;
  
  extern void console_init(void);
  extern int vcs_init(void);
  
  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_ldisc(int disc, struct tty_ldisc *new_ldisc);
  extern int tty_register_driver(struct tty_driver *driver);
  extern int tty_unregister_driver(struct tty_driver *driver);
  extern void tty_register_device(struct tty_driver *driver, unsigned index, struct device *dev);
  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 is_orphaned_pgrp(int pgrp);
  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_unhangup(struct file *filp);
  extern int tty_hung_up_p(struct file * filp);
  extern void do_SAK(struct tty_struct *tty);
  extern void disassociate_ctty(int priv);
  extern void tty_flip_buffer_push(struct tty_struct *tty);
  extern int tty_get_baud_rate(struct tty_struct *tty);
  extern int tty_termios_baud_rate(struct termios *termios);
  
  /* n_tty.c */
  extern struct tty_ldisc tty_ldisc_N_TTY;
  
  /* tty_ioctl.c */
  extern int n_tty_ioctl(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);
  
  /* printk.c */
  
  extern void console_print(const char *);
  
  /* vt.c */
  
  extern int vt_ioctl(struct tty_struct *tty, struct file * file,
  		    unsigned int cmd, unsigned long arg);
  
  static inline dev_t tty_devnum(struct tty_struct *tty)
  {
  	return MKDEV(tty->driver->major, tty->driver->minor_start) + tty->index;
  }
  
  #endif /* __KERNEL__ */
  #endif
  