tty_ldisc.h

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#ifndef _LINUX_TTY_LDISC_H
#define _LINUX_TTY_LDISC_H

/*
 * This structure defines the interface between the tty line discipline
 * implementation 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 *);
 *
 *  This function is called when the line discipline is associated
 *  with the tty.  The line discipline can use this as an
 *  opportunity to initialize any state needed by the ldisc routines.
 * 
 * void (*close)(struct tty_struct *);
 *
 *  This function is called when the line discipline is being
 *  shutdown, either because the tty is being closed or because
 *  the tty is being changed to use a new line discipline
 * 
 * void (*flush_buffer)(struct tty_struct *tty);
 *
 *  This function instructs the line discipline to clear its
 *  buffers of any input characters it may have queued to be
 *  delivered to the user mode process.
 * 
 * ssize_t (*chars_in_buffer)(struct tty_struct *tty);
 *
 *  This function returns the number of input characters the line
 *  discipline may have queued up to be delivered to the user mode
 *  process.
 * 
 * ssize_t (*read)(struct tty_struct * tty, struct file * file,
 *         unsigned char * buf, size_t nr);
 *
 *  This function is called when the user requests to read from
 *  the tty.  The line discipline will return whatever characters
 *  it has buffered up for the user.  If this function is not
 *  defined, the user will receive an EIO error.
 * 
 * ssize_t (*write)(struct tty_struct * tty, struct file * file,
 *          const unsigned char * buf, size_t nr);
 *
 *  This function is called when the user requests to write to the
 *  tty.  The line discipline will deliver the characters to the
 *  low-level tty device for transmission, optionally performing
 *  some processing on the characters first.  If this function is
 *  not defined, the user will receive an EIO error.
 * 
 * int  (*ioctl)(struct tty_struct * tty, struct file * file,
 *       unsigned int cmd, unsigned long arg);
 *
 *  This function is called when the user requests an ioctl which
 *  is not handled by the tty layer or the low-level tty driver.
 *  It is intended for ioctls which affect line discpline
 *  operation.  Note that the search order for ioctls is (1) tty
 *  layer, (2) tty low-level driver, (3) line discpline.  So a
 *  low-level driver can "grab" an ioctl request before the line
 *  discpline has a chance to see it.
 * 
 * long (*compat_ioctl)(struct tty_struct * tty, struct file * file,
 *              unsigned int cmd, unsigned long arg);
 *
 *      Process ioctl calls from 32-bit process on 64-bit system
 *
 * void (*set_termios)(struct tty_struct *tty, struct ktermios * old);
 *
 *  This function notifies the line discpline that a change has
 *  been made to the termios structure.
 * 
 * int  (*poll)(struct tty_struct * tty, struct file * file,
 *        poll_table *wait);
 *
 *  This function is called when a user attempts to select/poll on a
 *  tty device.  It is solely the responsibility of the line
 *  discipline to handle poll requests.
 *
 * void (*receive_buf)(struct tty_struct *, const unsigned char *cp,
 *             char *fp, int count);
 *
 *  This function is called by the low-level tty driver to send
 *  characters received by the hardware to the line discpline for
 *  processing.  <cp> is a pointer to the buffer of input
 *  character received by the device.  <fp> is a pointer to a
 *  pointer of flag bytes which indicate whether a character was
 *  received with a parity error, etc.
 * 
 * void (*write_wakeup)(struct tty_struct *);
 *
 *  This function is called by the low-level tty driver to signal
 *  that line discpline should try to send more characters to the
 *  low-level driver for transmission.  If the line discpline does
 *  not have any more data to send, it can just return.
 *
 * int (*hangup)(struct tty_struct *)
 *
 *  Called on a hangup. Tells the discipline that it should
 *  cease I/O to the tty driver. Can sleep. The driver should
 *  seek to perform this action quickly but should wait until
 *  any pending driver I/O is completed.
 *
 * void (*dcd_change)(struct tty_struct *tty, unsigned int status,
 *          struct pps_event_time *ts)
 *
 *  Tells the discipline that the DCD pin has changed its status and
 *  the relative timestamp. Pointer ts cannot be NULL.
 */

#include <linux/fs.h>
#include <linux/wait.h>
#include <linux/pps_kernel.h>
#include <linux/wait.h>

struct tty_ldisc_ops {
    int magic;
    char    *name;
    int num;
    int flags;
    
    /*
     * The following routines are called from above.
     */
    int (*open)(struct tty_struct *);
    void    (*close)(struct tty_struct *);
    void    (*flush_buffer)(struct tty_struct *tty);
    ssize_t (*chars_in_buffer)(struct tty_struct *tty);
    ssize_t (*read)(struct tty_struct * tty, struct file * file,
            unsigned char __user * buf, size_t nr);
    ssize_t (*write)(struct tty_struct * tty, struct file * file,
             const unsigned char * buf, size_t nr); 
    int (*ioctl)(struct tty_struct * tty, struct file * file,
             unsigned int cmd, unsigned long arg);
    long    (*compat_ioctl)(struct tty_struct * tty, struct file * file,
                unsigned int cmd, unsigned long arg);
    void    (*set_termios)(struct tty_struct *tty, struct ktermios * old);
    unsigned int (*poll)(struct tty_struct *, struct file *,
                 struct poll_table_struct *);
    int (*hangup)(struct tty_struct *tty);
    
    /*
     * The following routines are called from below.
     */
    void    (*receive_buf)(struct tty_struct *, const unsigned char *cp,
                   char *fp, int count);
    void    (*write_wakeup)(struct tty_struct *);
    void    (*dcd_change)(struct tty_struct *, unsigned int,
                struct pps_event_time *);

    struct  module *owner;
    
    int refcount;
};

struct tty_ldisc {
    struct tty_ldisc_ops *ops;
    atomic_t users;
    wait_queue_head_t wq_idle;
};

#define TTY_LDISC_MAGIC 0x5403

#define LDISC_FLAG_DEFINED  0x00000001

#define MODULE_ALIAS_LDISC(ldisc) \
    MODULE_ALIAS("tty-ldisc-" __stringify(ldisc))

#endif /* _LINUX_TTY_LDISC_H */