include/linux/tty_ldisc.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef _LINUX_TTY_LDISC_H
   3 #define _LINUX_TTY_LDISC_H
   4
   5 /*
   6  * This structure defines the interface between the tty line discipline
   7  * implementation and the tty routines.  The following routines can be
   8  * defined; unless noted otherwise, they are optional, and can be
   9  * filled in with a null pointer.
  10  *
  11  * int  (*open)(struct tty_struct *);
  12  *
  13  *      This function is called when the line discipline is associated
  14  *      with the tty.  The line discipline can use this as an
  15  *      opportunity to initialize any state needed by the ldisc routines.
  16  *
  17  * void (*close)(struct tty_struct *);
  18  *
  19  *      This function is called when the line discipline is being
  20  *      shutdown, either because the tty is being closed or because
  21  *      the tty is being changed to use a new line discipline
  22  *
  23  * void (*flush_buffer)(struct tty_struct *tty);
  24  *
  25  *      This function instructs the line discipline to clear its
  26  *      buffers of any input characters it may have queued to be
  27  *      delivered to the user mode process.
  28  *
  29  * ssize_t (*read)(struct tty_struct * tty, struct file * file,
  30  *                 unsigned char * buf, size_t nr);
  31  *
  32  *      This function is called when the user requests to read from
  33  *      the tty.  The line discipline will return whatever characters
  34  *      it has buffered up for the user.  If this function is not
  35  *      defined, the user will receive an EIO error.
  36  *
  37  * ssize_t (*write)(struct tty_struct * tty, struct file * file,
  38  *                  const unsigned char * buf, size_t nr);
  39  *
  40  *      This function is called when the user requests to write to the
  41  *      tty.  The line discipline will deliver the characters to the
  42  *      low-level tty device for transmission, optionally performing
  43  *      some processing on the characters first.  If this function is
  44  *      not defined, the user will receive an EIO error.
  45  *
  46  * int  (*ioctl)(struct tty_struct * tty, struct file * file,
  47  *               unsigned int cmd, unsigned long arg);
  48  *
  49  *      This function is called when the user requests an ioctl which
  50  *      is not handled by the tty layer or the low-level tty driver.
  51  *      It is intended for ioctls which affect line discpline
  52  *      operation.  Note that the search order for ioctls is (1) tty
  53  *      layer, (2) tty low-level driver, (3) line discpline.  So a
  54  *      low-level driver can "grab" an ioctl request before the line
  55  *      discpline has a chance to see it.
  56  *
  57  * int  (*compat_ioctl)(struct tty_struct * tty, struct file * file,
  58  *                      unsigned int cmd, unsigned long arg);
  59  *
  60  *      Process ioctl calls from 32-bit process on 64-bit system
  61  *
  62  *      NOTE: only ioctls that are neither "pointer to compatible
  63  *      structure" nor tty-generic.  Something private that takes
  64  *      an integer or a pointer to wordsize-sensitive structure
  65  *      belongs here, but most of ldiscs will happily leave
  66  *      it NULL.
  67  *
  68  * void (*set_termios)(struct tty_struct *tty, struct ktermios * old);
  69  *
  70  *      This function notifies the line discpline that a change has
  71  *      been made to the termios structure.
  72  *
  73  * int  (*poll)(struct tty_struct * tty, struct file * file,
  74  *                poll_table *wait);
  75  *
  76  *      This function is called when a user attempts to select/poll on a
  77  *      tty device.  It is solely the responsibility of the line
  78  *      discipline to handle poll requests.
  79  *
  80  * void (*receive_buf)(struct tty_struct *, const unsigned char *cp,
  81  *                     char *fp, int count);
  82  *
  83  *      This function is called by the low-level tty driver to send
  84  *      characters received by the hardware to the line discpline for
  85  *      processing.  <cp> is a pointer to the buffer of input
  86  *      character received by the device.  <fp> is a pointer to a
  87  *      pointer of flag bytes which indicate whether a character was
  88  *      received with a parity error, etc. <fp> may be NULL to indicate
  89  *      all data received is TTY_NORMAL.
  90  *
  91  * void (*write_wakeup)(struct tty_struct *);
  92  *
  93  *      This function is called by the low-level tty driver to signal
  94  *      that line discpline should try to send more characters to the
  95  *      low-level driver for transmission.  If the line discpline does
  96  *      not have any more data to send, it can just return. If the line
  97  *      discipline does have some data to send, please arise a tasklet
  98  *      or workqueue to do the real data transfer. Do not send data in
  99  *      this hook, it may leads to a deadlock.
 100  *
 101  * int (*hangup)(struct tty_struct *)
 102  *
 103  *      Called on a hangup. Tells the discipline that it should
 104  *      cease I/O to the tty driver. Can sleep. The driver should
 105  *      seek to perform this action quickly but should wait until
 106  *      any pending driver I/O is completed.
 107  *
 108  * void (*dcd_change)(struct tty_struct *tty, unsigned int status)
 109  *
 110  *      Tells the discipline that the DCD pin has changed its status.
 111  *      Used exclusively by the N_PPS (Pulse-Per-Second) line discipline.
 112  *
 113  * int  (*receive_buf2)(struct tty_struct *, const unsigned char *cp,
 114  *                      char *fp, int count);
 115  *
 116  *      This function is called by the low-level tty driver to send
 117  *      characters received by the hardware to the line discpline for
 118  *      processing.  <cp> is a pointer to the buffer of input
 119  *      character received by the device.  <fp> is a pointer to a
 120  *      pointer of flag bytes which indicate whether a character was
 121  *      received with a parity error, etc. <fp> may be NULL to indicate
 122  *      all data received is TTY_NORMAL.
 123  *      If assigned, prefer this function for automatic flow control.
 124  */
 125
 126 #include <linux/fs.h>
 127 #include <linux/wait.h>
 128 #include <linux/atomic.h>
 129
 130 /*
 131  * the semaphore definition
 132  */
 133 struct ld_semaphore {
 134         atomic_long_t           count;
 135         raw_spinlock_t          wait_lock;
 136         unsigned int            wait_readers;
 137         struct list_head        read_wait;
 138         struct list_head        write_wait;
 139 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 140         struct lockdep_map      dep_map;
 141 #endif
 142 };
 143
 144 extern void __init_ldsem(struct ld_semaphore *sem, const char *name,
 145                          struct lock_class_key *key);
 146
 147 #define init_ldsem(sem)                                         \
 148 do {                                                            \
 149         static struct lock_class_key __key;                     \
 150                                                                 \
 151         __init_ldsem((sem), #sem, &__key);                      \
 152 } while (0)
 153
 154
 155 extern int ldsem_down_read(struct ld_semaphore *sem, long timeout);
 156 extern int ldsem_down_read_trylock(struct ld_semaphore *sem);
 157 extern int ldsem_down_write(struct ld_semaphore *sem, long timeout);
 158 extern int ldsem_down_write_trylock(struct ld_semaphore *sem);
 159 extern void ldsem_up_read(struct ld_semaphore *sem);
 160 extern void ldsem_up_write(struct ld_semaphore *sem);
 161
 162 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 163 extern int ldsem_down_read_nested(struct ld_semaphore *sem, int subclass,
 164                                   long timeout);
 165 extern int ldsem_down_write_nested(struct ld_semaphore *sem, int subclass,
 166                                    long timeout);
 167 #else
 168 # define ldsem_down_read_nested(sem, subclass, timeout)         \
 169                 ldsem_down_read(sem, timeout)
 170 # define ldsem_down_write_nested(sem, subclass, timeout)        \
 171                 ldsem_down_write(sem, timeout)
 172 #endif
 173
 174
 175 struct tty_ldisc_ops {
 176         int     magic;
 177         char    *name;
 178         int     num;
 179         int     flags;
 180
 181         /*
 182          * The following routines are called from above.
 183          */
 184         int     (*open)(struct tty_struct *);
 185         void    (*close)(struct tty_struct *);
 186         void    (*flush_buffer)(struct tty_struct *tty);
 187         ssize_t (*read)(struct tty_struct *tty, struct file *file,
 188                         unsigned char __user *buf, size_t nr);
 189         ssize_t (*write)(struct tty_struct *tty, struct file *file,
 190                          const unsigned char *buf, size_t nr);
 191         int     (*ioctl)(struct tty_struct *tty, struct file *file,
 192                          unsigned int cmd, unsigned long arg);
 193         int     (*compat_ioctl)(struct tty_struct *tty, struct file *file,
 194                                 unsigned int cmd, unsigned long arg);
 195         void    (*set_termios)(struct tty_struct *tty, struct ktermios *old);
 196         __poll_t (*poll)(struct tty_struct *, struct file *,
 197                              struct poll_table_struct *);
 198         int     (*hangup)(struct tty_struct *tty);
 199
 200         /*
 201          * The following routines are called from below.
 202          */
 203         void    (*receive_buf)(struct tty_struct *, const unsigned char *cp,
 204                                char *fp, int count);
 205         void    (*write_wakeup)(struct tty_struct *);
 206         void    (*dcd_change)(struct tty_struct *, unsigned int);
 207         int     (*receive_buf2)(struct tty_struct *, const unsigned char *cp,
 208                                 char *fp, int count);
 209
 210         struct  module *owner;
 211
 212         int refcount;
 213 };
 214
 215 struct tty_ldisc {
 216         struct tty_ldisc_ops *ops;
 217         struct tty_struct *tty;
 218 };
 219
 220 #define TTY_LDISC_MAGIC 0x5403
 221
 222 #define LDISC_FLAG_DEFINED      0x00000001
 223
 224 #define MODULE_ALIAS_LDISC(ldisc) \
 225         MODULE_ALIAS("tty-ldisc-" __stringify(ldisc))
 226
 227 #endif /* _LINUX_TTY_LDISC_H */