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. If the line
  96  *      discipline does have some data to send, please arise a tasklet
  97  *      or workqueue to do the real data transfer. Do not send data in
  98  *      this hook, it may leads to a deadlock.
  99  *
 100  * int (*hangup)(struct tty_struct *)
 101  *
 102  *      Called on a hangup. Tells the discipline that it should
 103  *      cease I/O to the tty driver. Can sleep. The driver should
 104  *      seek to perform this action quickly but should wait until
 105  *      any pending driver I/O is completed.
 106  *
 107  * void (*fasync)(struct tty_struct *, int on)
 108  *
 109  *      Notify line discipline when signal-driven I/O is enabled or
 110  *      disabled.
 111  *
 112  * void (*dcd_change)(struct tty_struct *tty, unsigned int status)
 113  *
 114  *      Tells the discipline that the DCD pin has changed its status.
 115  *      Used exclusively by the N_PPS (Pulse-Per-Second) line discipline.
 116  *
 117  * int  (*receive_buf2)(struct tty_struct *, const unsigned char *cp,
 118  *                      char *fp, int count);
 119  *
 120  *      This function is called by the low-level tty driver to send
 121  *      characters received by the hardware to the line discpline for
 122  *      processing.  <cp> is a pointer to the buffer of input
 123  *      character received by the device.  <fp> is a pointer to a
 124  *      pointer of flag bytes which indicate whether a character was
 125  *      received with a parity error, etc. <fp> may be NULL to indicate
 126  *      all data received is TTY_NORMAL.
 127  *      If assigned, prefer this function for automatic flow control.
 128  */
 129
 130 #include <linux/fs.h>
 131 #include <linux/wait.h>
 132
 133
 134 /*
 135  * the semaphore definition
 136  */
 137 struct ld_semaphore {
 138         long                    count;
 139         raw_spinlock_t          wait_lock;
 140         unsigned int            wait_readers;
 141         struct list_head        read_wait;
 142         struct list_head        write_wait;
 143 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 144         struct lockdep_map      dep_map;
 145 #endif
 146 };
 147
 148 extern void __init_ldsem(struct ld_semaphore *sem, const char *name,
 149                          struct lock_class_key *key);
 150
 151 #define init_ldsem(sem)                                         \
 152 do {                                                            \
 153         static struct lock_class_key __key;                     \
 154                                                                 \
 155         __init_ldsem((sem), #sem, &__key);                      \
 156 } while (0)
 157
 158
 159 extern int ldsem_down_read(struct ld_semaphore *sem, long timeout);
 160 extern int ldsem_down_read_trylock(struct ld_semaphore *sem);
 161 extern int ldsem_down_write(struct ld_semaphore *sem, long timeout);
 162 extern int ldsem_down_write_trylock(struct ld_semaphore *sem);
 163 extern void ldsem_up_read(struct ld_semaphore *sem);
 164 extern void ldsem_up_write(struct ld_semaphore *sem);
 165
 166 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 167 extern int ldsem_down_read_nested(struct ld_semaphore *sem, int subclass,
 168                                   long timeout);
 169 extern int ldsem_down_write_nested(struct ld_semaphore *sem, int subclass,
 170                                    long timeout);
 171 #else
 172 # define ldsem_down_read_nested(sem, subclass, timeout)         \
 173                 ldsem_down_read(sem, timeout)
 174 # define ldsem_down_write_nested(sem, subclass, timeout)        \
 175                 ldsem_down_write(sem, timeout)
 176 #endif
 177
 178
 179 struct tty_ldisc_ops {
 180         int     magic;
 181         char    *name;
 182         int     num;
 183         int     flags;
 184
 185         /*
 186          * The following routines are called from above.
 187          */
 188         int     (*open)(struct tty_struct *);
 189         void    (*close)(struct tty_struct *);
 190         void    (*flush_buffer)(struct tty_struct *tty);
 191         ssize_t (*chars_in_buffer)(struct tty_struct *tty);
 192         ssize_t (*read)(struct tty_struct *tty, struct file *file,
 193                         unsigned char __user *buf, size_t nr);
 194         ssize_t (*write)(struct tty_struct *tty, struct file *file,
 195                          const unsigned char *buf, size_t nr);
 196         int     (*ioctl)(struct tty_struct *tty, struct file *file,
 197                          unsigned int cmd, unsigned long arg);
 198         long    (*compat_ioctl)(struct tty_struct *tty, struct file *file,
 199                                 unsigned int cmd, unsigned long arg);
 200         void    (*set_termios)(struct tty_struct *tty, struct ktermios *old);
 201         unsigned int (*poll)(struct tty_struct *, struct file *,
 202                              struct poll_table_struct *);
 203         int     (*hangup)(struct tty_struct *tty);
 204
 205         /*
 206          * The following routines are called from below.
 207          */
 208         void    (*receive_buf)(struct tty_struct *, const unsigned char *cp,
 209                                char *fp, int count);
 210         void    (*write_wakeup)(struct tty_struct *);
 211         void    (*dcd_change)(struct tty_struct *, unsigned int);
 212         void    (*fasync)(struct tty_struct *tty, int on);
 213         int     (*receive_buf2)(struct tty_struct *, const unsigned char *cp,
 214                                 char *fp, int count);
 215
 216         struct  module *owner;
 217
 218         int refcount;
 219 };
 220
 221 struct tty_ldisc {
 222         struct tty_ldisc_ops *ops;
 223         struct tty_struct *tty;
 224 };
 225
 226 #define TTY_LDISC_MAGIC 0x5403
 227
 228 #define LDISC_FLAG_DEFINED      0x00000001
 229
 230 #define MODULE_ALIAS_LDISC(ldisc) \
 231         MODULE_ALIAS("tty-ldisc-" __stringify(ldisc))
 232
 233 #endif /* _LINUX_TTY_LDISC_H */