linux/include/linux/tty_ldisc.h
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   1#ifndef _LINUX_TTY_LDISC_H
   2#define _LINUX_TTY_LDISC_H
   3
   4/*
   5 * This structure defines the interface between the tty line discipline
   6 * implementation and the tty routines.  The following routines can be
   7 * defined; unless noted otherwise, they are optional, and can be
   8 * filled in with a null pointer.
   9 *
  10 * int  (*open)(struct tty_struct *);
  11 *
  12 *      This function is called when the line discipline is associated
  13 *      with the tty.  The line discipline can use this as an
  14 *      opportunity to initialize any state needed by the ldisc routines.
  15 * 
  16 * void (*close)(struct tty_struct *);
  17 *
  18 *      This function is called when the line discipline is being
  19 *      shutdown, either because the tty is being closed or because
  20 *      the tty is being changed to use a new line discipline
  21 * 
  22 * void (*flush_buffer)(struct tty_struct *tty);
  23 *
  24 *      This function instructs the line discipline to clear its
  25 *      buffers of any input characters it may have queued to be
  26 *      delivered to the user mode process.
  27 * 
  28 * ssize_t (*chars_in_buffer)(struct tty_struct *tty);
  29 *
  30 *      This function returns the number of input characters the line
  31 *      discipline may have queued up to be delivered to the user mode
  32 *      process.
  33 * 
  34 * ssize_t (*read)(struct tty_struct * tty, struct file * file,
  35 *                 unsigned char * buf, size_t nr);
  36 *
  37 *      This function is called when the user requests to read from
  38 *      the tty.  The line discipline will return whatever characters
  39 *      it has buffered up for the user.  If this function is not
  40 *      defined, the user will receive an EIO error.
  41 * 
  42 * ssize_t (*write)(struct tty_struct * tty, struct file * file,
  43 *                  const unsigned char * buf, size_t nr);
  44 *
  45 *      This function is called when the user requests to write to the
  46 *      tty.  The line discipline will deliver the characters to the
  47 *      low-level tty device for transmission, optionally performing
  48 *      some processing on the characters first.  If this function is
  49 *      not defined, the user will receive an EIO error.
  50 * 
  51 * int  (*ioctl)(struct tty_struct * tty, struct file * file,
  52 *               unsigned int cmd, unsigned long arg);
  53 *
  54 *      This function is called when the user requests an ioctl which
  55 *      is not handled by the tty layer or the low-level tty driver.
  56 *      It is intended for ioctls which affect line discpline
  57 *      operation.  Note that the search order for ioctls is (1) tty
  58 *      layer, (2) tty low-level driver, (3) line discpline.  So a
  59 *      low-level driver can "grab" an ioctl request before the line
  60 *      discpline has a chance to see it.
  61 * 
  62 * long (*compat_ioctl)(struct tty_struct * tty, struct file * file,
  63 *                      unsigned int cmd, unsigned long arg);
  64 *
  65 *      Process ioctl calls from 32-bit process on 64-bit system
  66 *
  67 * void (*set_termios)(struct tty_struct *tty, struct ktermios * old);
  68 *
  69 *      This function notifies the line discpline that a change has
  70 *      been made to the termios structure.
  71 * 
  72 * int  (*poll)(struct tty_struct * tty, struct file * file,
  73 *                poll_table *wait);
  74 *
  75 *      This function is called when a user attempts to select/poll on a
  76 *      tty device.  It is solely the responsibility of the line
  77 *      discipline to handle poll requests.
  78 *
  79 * void (*receive_buf)(struct tty_struct *, const unsigned char *cp,
  80 *                     char *fp, int count);
  81 *
  82 *      This function is called by the low-level tty driver to send
  83 *      characters received by the hardware to the line discpline for
  84 *      processing.  <cp> is a pointer to the buffer of input
  85 *      character received by the device.  <fp> is a pointer to a
  86 *      pointer of flag bytes which indicate whether a character was
  87 *      received with a parity error, etc.
  88 * 
  89 * void (*write_wakeup)(struct tty_struct *);
  90 *
  91 *      This function is called by the low-level tty driver to signal
  92 *      that line discpline should try to send more characters to the
  93 *      low-level driver for transmission.  If the line discpline does
  94 *      not have any more data to send, it can just return.
  95 *
  96 * int (*hangup)(struct tty_struct *)
  97 *
  98 *      Called on a hangup. Tells the discipline that it should
  99 *      cease I/O to the tty driver. Can sleep. The driver should
 100 *      seek to perform this action quickly but should wait until
 101 *      any pending driver I/O is completed.
 102 *
 103 * void (*dcd_change)(struct tty_struct *tty, unsigned int status)
 104 *
 105 *      Tells the discipline that the DCD pin has changed its status.
 106 *      Used exclusively by the N_PPS (Pulse-Per-Second) line discipline.
 107 */
 108
 109#include <linux/fs.h>
 110#include <linux/wait.h>
 111#include <linux/wait.h>
 112
 113struct tty_ldisc_ops {
 114        int     magic;
 115        char    *name;
 116        int     num;
 117        int     flags;
 118        
 119        /*
 120         * The following routines are called from above.
 121         */
 122        int     (*open)(struct tty_struct *);
 123        void    (*close)(struct tty_struct *);
 124        void    (*flush_buffer)(struct tty_struct *tty);
 125        ssize_t (*chars_in_buffer)(struct tty_struct *tty);
 126        ssize_t (*read)(struct tty_struct * tty, struct file * file,
 127                        unsigned char __user * buf, size_t nr);
 128        ssize_t (*write)(struct tty_struct * tty, struct file * file,
 129                         const unsigned char * buf, size_t nr); 
 130        int     (*ioctl)(struct tty_struct * tty, struct file * file,
 131                         unsigned int cmd, unsigned long arg);
 132        long    (*compat_ioctl)(struct tty_struct * tty, struct file * file,
 133                                unsigned int cmd, unsigned long arg);
 134        void    (*set_termios)(struct tty_struct *tty, struct ktermios * old);
 135        unsigned int (*poll)(struct tty_struct *, struct file *,
 136                             struct poll_table_struct *);
 137        int     (*hangup)(struct tty_struct *tty);
 138        
 139        /*
 140         * The following routines are called from below.
 141         */
 142        void    (*receive_buf)(struct tty_struct *, const unsigned char *cp,
 143                               char *fp, int count);
 144        void    (*write_wakeup)(struct tty_struct *);
 145        void    (*dcd_change)(struct tty_struct *, unsigned int);
 146
 147        struct  module *owner;
 148        
 149        int refcount;
 150};
 151
 152struct tty_ldisc {
 153        struct tty_ldisc_ops *ops;
 154        atomic_t users;
 155        wait_queue_head_t wq_idle;
 156};
 157
 158#define TTY_LDISC_MAGIC 0x5403
 159
 160#define LDISC_FLAG_DEFINED      0x00000001
 161
 162#define MODULE_ALIAS_LDISC(ldisc) \
 163        MODULE_ALIAS("tty-ldisc-" __stringify(ldisc))
 164
 165#endif /* _LINUX_TTY_LDISC_H */
 166
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