include/linux/tty_ldisc.h

   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  * void (*set_termios)(struct tty_struct *tty, struct termios * old);
  63  *
  64  *      This function notifies the line discpline that a change has
  65  *      been made to the termios structure.
  66  *
  67  * int  (*poll)(struct tty_struct * tty, struct file * file,
  68  *                poll_table *wait);
  69  *
  70  *      This function is called when a user attempts to select/poll on a
  71  *      tty device.  It is solely the responsibility of the line
  72  *      discipline to handle poll requests.
  73  *
  74  * void (*receive_buf)(struct tty_struct *, const unsigned char *cp,
  75  *                     char *fp, int count);
  76  *
  77  *      This function is called by the low-level tty driver to send
  78  *      characters received by the hardware to the line discpline for
  79  *      processing.  <cp> is a pointer to the buffer of input
  80  *      character received by the device.  <fp> is a pointer to a
  81  *      pointer of flag bytes which indicate whether a character was
  82  *      received with a parity error, etc.
  83  *
  84  * int  (*receive_room)(struct tty_struct *);
  85  *
  86  *      This function is called by the low-level tty driver to
  87  *      determine how many characters the line discpline can accept.
  88  *      The low-level driver must not send more characters than was
  89  *      indicated by receive_room, or the line discpline may drop
  90  *      those characters.
  91  *
  92  * void (*write_wakeup)(struct tty_struct *);
  93  *
  94  *      This function is called by the low-level tty driver to signal
  95  *      that line discpline should try to send more characters to the
  96  *      low-level driver for transmission.  If the line discpline does
  97  *      not have any more data to send, it can just return.
  98  *
  99  * int (*hangup)(struct tty_struct *)
 100  *
 101  *      Called on a hangup. Tells the discipline that it should
 102  *      cease I/O to the tty driver. Can sleep. The driver should
 103  *      seek to perform this action quickly but should wait until
 104  *      any pending driver I/O is completed.
 105  */
 106
 107 #include <linux/fs.h>
 108 #include <linux/wait.h>
 109
 110 struct tty_ldisc {
 111         int     magic;
 112         char    *name;
 113         int     num;
 114         int     flags;
 115
 116         /*
 117          * The following routines are called from above.
 118          */
 119         int     (*open)(struct tty_struct *);
 120         void    (*close)(struct tty_struct *);
 121         void    (*flush_buffer)(struct tty_struct *tty);
 122         ssize_t (*chars_in_buffer)(struct tty_struct *tty);
 123         ssize_t (*read)(struct tty_struct * tty, struct file * file,
 124                         unsigned char __user * buf, size_t nr);
 125         ssize_t (*write)(struct tty_struct * tty, struct file * file,
 126                          const unsigned char __user * buf, size_t nr);
 127         int     (*ioctl)(struct tty_struct * tty, struct file * file,
 128                          unsigned int cmd, unsigned long arg);
 129         void    (*set_termios)(struct tty_struct *tty, struct termios * old);
 130         unsigned int (*poll)(struct tty_struct *, struct file *,
 131                              struct poll_table_struct *);
 132         int     (*hangup)(struct tty_struct *tty);
 133
 134         /*
 135          * The following routines are called from below.
 136          */
 137         void    (*receive_buf)(struct tty_struct *, const unsigned char *cp,
 138                                char *fp, int count);
 139         int     (*receive_room)(struct tty_struct *);
 140         void    (*write_wakeup)(struct tty_struct *);
 141
 142         struct  module *owner;
 143
 144         int refcount;
 145 };
 146
 147 #define TTY_LDISC_MAGIC 0x5403
 148
 149 #define LDISC_FLAG_DEFINED      0x00000001
 150
 151 #define MODULE_ALIAS_LDISC(ldisc) \
 152         MODULE_ALIAS("tty-ldisc-" __stringify(ldisc))
 153
 154 #endif /* _LINUX_TTY_LDISC_H */