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  * 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. <fp> may be NULL to indicate
  88  *      all data received is TTY_NORMAL.
  89  *
  90  * void (*write_wakeup)(struct tty_struct *);
  91  *
  92  *      This function is called by the low-level tty driver to signal
  93  *      that line discpline should try to send more characters to the
  94  *      low-level driver for transmission.  If the line discpline does
  95  *      not have any more data to send, it can just return.
  96  *
  97  * int (*hangup)(struct tty_struct *)
  98  *
  99  *      Called on a hangup. Tells the discipline that it should
 100  *      cease I/O to the tty driver. Can sleep. The driver should
 101  *      seek to perform this action quickly but should wait until
 102  *      any pending driver I/O is completed.
 103  *
 104  * void (*fasync)(struct tty_struct *, int on)
 105  *
 106  *      Notify line discipline when signal-driven I/O is enabled or
 107  *      disabled.
 108  *
 109  * void (*dcd_change)(struct tty_struct *tty, unsigned int status)
 110  *
 111  *      Tells the discipline that the DCD pin has changed its status.
 112  *      Used exclusively by the N_PPS (Pulse-Per-Second) line discipline.
 113  *
 114  * int  (*receive_buf2)(struct tty_struct *, const unsigned char *cp,
 115  *                      char *fp, int count);
 116  *
 117  *      This function is called by the low-level tty driver to send
 118  *      characters received by the hardware to the line discpline for
 119  *      processing.  <cp> is a pointer to the buffer of input
 120  *      character received by the device.  <fp> is a pointer to a
 121  *      pointer of flag bytes which indicate whether a character was
 122  *      received with a parity error, etc. <fp> may be NULL to indicate
 123  *      all data received is TTY_NORMAL.
 124  *      If assigned, prefer this function for automatic flow control.
 125  */
 126
 127 #include <linux/fs.h>
 128 #include <linux/wait.h>
 129
 130
 131 /*
 132  * the semaphore definition
 133  */
 134 struct ld_semaphore {
 135         long                    count;
 136         raw_spinlock_t          wait_lock;
 137         unsigned int            wait_readers;
 138         struct list_head        read_wait;
 139         struct list_head        write_wait;
 140 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 141         struct lockdep_map      dep_map;
 142 #endif
 143 };
 144
 145 extern void __init_ldsem(struct ld_semaphore *sem, const char *name,
 146                          struct lock_class_key *key);
 147
 148 #define init_ldsem(sem)                                         \
 149 do {                                                            \
 150         static struct lock_class_key __key;                     \
 151                                                                 \
 152         __init_ldsem((sem), #sem, &__key);                      \
 153 } while (0)
 154
 155
 156 extern int ldsem_down_read(struct ld_semaphore *sem, long timeout);
 157 extern int ldsem_down_read_trylock(struct ld_semaphore *sem);
 158 extern int ldsem_down_write(struct ld_semaphore *sem, long timeout);
 159 extern int ldsem_down_write_trylock(struct ld_semaphore *sem);
 160 extern void ldsem_up_read(struct ld_semaphore *sem);
 161 extern void ldsem_up_write(struct ld_semaphore *sem);
 162
 163 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 164 extern int ldsem_down_read_nested(struct ld_semaphore *sem, int subclass,
 165                                   long timeout);
 166 extern int ldsem_down_write_nested(struct ld_semaphore *sem, int subclass,
 167                                    long timeout);
 168 #else
 169 # define ldsem_down_read_nested(sem, subclass, timeout)         \
 170                 ldsem_down_read(sem, timeout)
 171 # define ldsem_down_write_nested(sem, subclass, timeout)        \
 172                 ldsem_down_write(sem, timeout)
 173 #endif
 174
 175
 176 struct tty_ldisc_ops {
 177         int     magic;
 178         char    *name;
 179         int     num;
 180         int     flags;
 181
 182         /*
 183          * The following routines are called from above.
 184          */
 185         int     (*open)(struct tty_struct *);
 186         void    (*close)(struct tty_struct *);
 187         void    (*flush_buffer)(struct tty_struct *tty);
 188         ssize_t (*chars_in_buffer)(struct tty_struct *tty);
 189         ssize_t (*read)(struct tty_struct *tty, struct file *file,
 190                         unsigned char __user *buf, size_t nr);
 191         ssize_t (*write)(struct tty_struct *tty, struct file *file,
 192                          const unsigned char *buf, size_t nr);
 193         int     (*ioctl)(struct tty_struct *tty, struct file *file,
 194                          unsigned int cmd, unsigned long arg);
 195         long    (*compat_ioctl)(struct tty_struct *tty, struct file *file,
 196                                 unsigned int cmd, unsigned long arg);
 197         void    (*set_termios)(struct tty_struct *tty, struct ktermios *old);
 198         unsigned int (*poll)(struct tty_struct *, struct file *,
 199                              struct poll_table_struct *);
 200         int     (*hangup)(struct tty_struct *tty);
 201
 202         /*
 203          * The following routines are called from below.
 204          */
 205         void    (*receive_buf)(struct tty_struct *, const unsigned char *cp,
 206                                char *fp, int count);
 207         void    (*write_wakeup)(struct tty_struct *);
 208         void    (*dcd_change)(struct tty_struct *, unsigned int);
 209         void    (*fasync)(struct tty_struct *tty, int on);
 210         int     (*receive_buf2)(struct tty_struct *, const unsigned char *cp,
 211                                 char *fp, int count);
 212
 213         struct  module *owner;
 214
 215         int refcount;
 216 };
 217
 218 struct tty_ldisc {
 219         struct tty_ldisc_ops *ops;
 220         struct tty_struct *tty;
 221 };
 222
 223 #define TTY_LDISC_MAGIC 0x5403
 224
 225 #define LDISC_FLAG_DEFINED      0x00000001
 226
 227 #define MODULE_ALIAS_LDISC(ldisc) \
 228         MODULE_ALIAS("tty-ldisc-" __stringify(ldisc))
 229
 230 #endif /* _LINUX_TTY_LDISC_H */