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tty_driver.h

#ifndef _LINUX_TTY_DRIVER_H
#define _LINUX_TTY_DRIVER_H

/*
 * This structure defines the interface between the low-level tty
 * driver and the tty routines.  The following routines can be
 * defined; unless noted otherwise, they are optional, and can be
 * filled in with a null pointer.
 *
 * int  (*open)(struct tty_struct * tty, struct file * filp);
 *
 *    This routine is called when a particular tty device is opened.
 *    This routine is mandatory; if this routine is not filled in,
 *    the attempted open will fail with ENODEV.
 *     
 * void (*close)(struct tty_struct * tty, struct file * filp);
 *
 *    This routine is called when a particular tty device is closed.
 *
 * int (*write)(struct tty_struct * tty, int from_user,
 *           const unsigned char *buf, int count);
 *
 *    This routine is called by the kernel to write a series of
 *    characters to the tty device.  The characters may come from
 *    user space or kernel space.  This routine will return the
 *    number of characters actually accepted for writing.  This
 *    routine is mandatory.
 *
 * void (*put_char)(struct tty_struct *tty, unsigned char ch);
 *
 *    This routine is called by the kernel to write a single
 *    character to the tty device.  If the kernel uses this routine,
 *    it must call the flush_chars() routine (if defined) when it is
 *    done stuffing characters into the driver.  If there is no room
 *    in the queue, the character is ignored.
 *
 * void (*flush_chars)(struct tty_struct *tty);
 *
 *    This routine is called by the kernel after it has written a
 *    series of characters to the tty device using put_char().  
 * 
 * int  (*write_room)(struct tty_struct *tty);
 *
 *    This routine returns the numbers of characters the tty driver
 *    will accept for queuing to be written.  This number is subject
 *    to change as output buffers get emptied, or if the output flow
 *    control is acted.
 * 
 * int  (*ioctl)(struct tty_struct *tty, struct file * file,
 *        unsigned int cmd, unsigned long arg);
 *
 *    This routine allows the tty driver to implement
 *    device-specific ioctl's.  If the ioctl number passed in cmd
 *    is not recognized by the driver, it should return ENOIOCTLCMD.
 * 
 * void (*set_termios)(struct tty_struct *tty, struct termios * old);
 *
 *    This routine allows the tty driver to be notified when
 *    device's termios settings have changed.  Note that a
 *    well-designed tty driver should be prepared to accept the case
 *    where old == NULL, and try to do something rational.
 *
 * void (*set_ldisc)(struct tty_struct *tty);
 *
 *    This routine allows the tty driver to be notified when the
 *    device's termios settings have changed.
 * 
 * void (*throttle)(struct tty_struct * tty);
 *
 *    This routine notifies the tty driver that input buffers for
 *    the line discipline are close to full, and it should somehow
 *    signal that no more characters should be sent to the tty.
 * 
 * void (*unthrottle)(struct tty_struct * tty);
 *
 *    This routine notifies the tty drivers that it should signals
 *    that characters can now be sent to the tty without fear of
 *    overrunning the input buffers of the line disciplines.
 * 
 * void (*stop)(struct tty_struct *tty);
 *
 *    This routine notifies the tty driver that it should stop
 *    outputting characters to the tty device.  
 * 
 * void (*start)(struct tty_struct *tty);
 *
 *    This routine notifies the tty driver that it resume sending
 *    characters to the tty device.
 * 
 * void (*hangup)(struct tty_struct *tty);
 *
 *    This routine notifies the tty driver that it should hangup the
 *    tty device.
 *
 * void (*break_ctl)(struct tty_stuct *tty, int state);
 *
 *    This optional routine requests the tty driver to turn on or
 *    off BREAK status on the RS-232 port.  If state is -1,
 *    then the BREAK status should be turned on; if state is 0, then
 *    BREAK should be turned off.
 *
 *    If this routine is implemented, the high-level tty driver will
 *    handle the following ioctls: TCSBRK, TCSBRKP, TIOCSBRK,
 *    TIOCCBRK.  Otherwise, these ioctls will be passed down to the
 *    driver to handle.
 *
 * void (*wait_until_sent)(struct tty_struct *tty, int timeout);
 * 
 *    This routine waits until the device has written out all of the
 *    characters in its transmitter FIFO.
 *
 * void (*send_xchar)(struct tty_struct *tty, char ch);
 *
 *    This routine is used to send a high-priority XON/XOFF
 *    character to the device.
 */

#include <linux/fs.h>

struct tty_driver {
      int   magic;            /* magic number for this structure */
      const char  *driver_name;
      const char  *name;
      int   name_base;  /* offset of printed name */
      short major;            /* major device number */
      short minor_start;      /* start of minor device number*/
      short num;        /* number of devices */
      short type;       /* type of tty driver */
      short subtype;    /* subtype of tty driver */
      struct termios init_termios; /* Initial termios */
      int   flags;            /* tty driver flags */
      int   *refcount;  /* for loadable tty drivers */
      struct semaphore tty_lock;/* access control for printk and tty layer */
      struct proc_dir_entry *proc_entry; /* /proc fs entry */
      struct tty_driver *other; /* only used for the PTY driver */

      /*
       * Pointer to the tty data structures
       */
      struct tty_struct **table;
      struct termios **termios;
      struct termios **termios_locked;
      void *driver_state;     /* only used for the PTY driver */
      
      /*
       * Interface routines from the upper tty layer to the tty
       * driver.
       */
      int  (*open)(struct tty_struct * tty, struct file * filp);
      void (*close)(struct tty_struct * tty, struct file * filp);
      int  (*write)(struct tty_struct * tty, int from_user,
                  const unsigned char *buf, int count);
      void (*put_char)(struct tty_struct *tty, unsigned char ch);
      void (*flush_chars)(struct tty_struct *tty);
      int  (*write_room)(struct tty_struct *tty);
      int  (*chars_in_buffer)(struct tty_struct *tty);
      int  (*ioctl)(struct tty_struct *tty, struct file * file,
                unsigned int cmd, unsigned long arg);
      void (*set_termios)(struct tty_struct *tty, struct termios * old);
      void (*throttle)(struct tty_struct * tty);
      void (*unthrottle)(struct tty_struct * tty);
      void (*stop)(struct tty_struct *tty);
      void (*start)(struct tty_struct *tty);
      void (*hangup)(struct tty_struct *tty);
      void (*break_ctl)(struct tty_struct *tty, int state);
      void (*flush_buffer)(struct tty_struct *tty);
      void (*set_ldisc)(struct tty_struct *tty);
      void (*wait_until_sent)(struct tty_struct *tty, int timeout);
      void (*send_xchar)(struct tty_struct *tty, char ch);
      int (*read_proc)(char *page, char **start, off_t off,
                    int count, int *eof, void *data);
      int (*write_proc)(struct file *file, const char *buffer,
                    unsigned long count, void *data);

      /*
       * linked list pointers
       */
      struct tty_driver *next;
      struct tty_driver *prev;
};

/* tty driver magic number */
#define TTY_DRIVER_MAGIC            0x5402

/*
 * tty driver flags
 * 
 * TTY_DRIVER_RESET_TERMIOS --- requests the tty layer to reset the
 *    termios setting when the last process has closed the device.
 *    Used for PTY's, in particular.
 * 
 * TTY_DRIVER_REAL_RAW --- if set, indicates that the driver will
 *    guarantee never not to set any special character handling
 *    flags if ((IGNBRK || (!BRKINT && !PARMRK)) && (IGNPAR ||
 *    !INPCK)).  That is, if there is no reason for the driver to
 *    send notifications of parity and break characters up to the
 *    line driver, it won't do so.  This allows the line driver to
 *    optimize for this case if this flag is set.  (Note that there
 *    is also a promise, if the above case is true, not to signal
 *    overruns, either.)
 *
 * TTY_DRIVER_NO_DEVFS --- if set, do not create devfs entries. This
 *    is only used by tty_register_driver().
 *
 * TTY_DRIVER_CONSOLE --- if set, indicates that this driver is also 
 *    used by printk. It is set by register_console. 
 */
#define TTY_DRIVER_INSTALLED        0x0001
#define TTY_DRIVER_RESET_TERMIOS    0x0002
#define TTY_DRIVER_REAL_RAW         0x0004
#define TTY_DRIVER_NO_DEVFS         0x0008
#define TTY_DRIVER_CONSOLE          0x0010

/* tty driver types */
#define TTY_DRIVER_TYPE_SYSTEM            0x0001
#define TTY_DRIVER_TYPE_CONSOLE           0x0002
#define TTY_DRIVER_TYPE_SERIAL            0x0003
#define TTY_DRIVER_TYPE_PTY         0x0004
#define TTY_DRIVER_TYPE_SCC         0x0005      /* scc driver */
#define TTY_DRIVER_TYPE_SYSCONS           0x0006

/* system subtypes (magic, used by tty_io.c) */
#define SYSTEM_TYPE_TTY             0x0001
#define SYSTEM_TYPE_CONSOLE         0x0002
#define SYSTEM_TYPE_SYSCONS         0x0003
#define SYSTEM_TYPE_SYSPTMX         0x0004

/* pty subtypes (magic, used by tty_io.c) */
#define PTY_TYPE_MASTER             0x0001
#define PTY_TYPE_SLAVE              0x0002

/* serial subtype definitions */
#define SERIAL_TYPE_NORMAL    1
#define SERIAL_TYPE_CALLOUT   2

#endif /* #ifdef _LINUX_TTY_DRIVER_H */

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