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  * long (*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  * void (*set_termios)(struct tty_struct *tty, struct ktermios * 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. <fp> may be NULL to indicate
  83  *      all data received is TTY_NORMAL.
  84  *
  85  * void (*write_wakeup)(struct tty_struct *);
  86  *
  87  *      This function is called by the low-level tty driver to signal
  88  *      that line discpline should try to send more characters to the
  89  *      low-level driver for transmission.  If the line discpline does
  90  *      not have any more data to send, it can just return. If the line
  91  *      discipline does have some data to send, please arise a tasklet
  92  *      or workqueue to do the real data transfer. Do not send data in
  93  *      this hook, it may leads to a deadlock.
  94  *
  95  * int (*hangup)(struct tty_struct *)
  96  *
  97  *      Called on a hangup. Tells the discipline that it should
  98  *      cease I/O to the tty driver. Can sleep. The driver should
  99  *      seek to perform this action quickly but should wait until
 100  *      any pending driver I/O is completed.
 101  *
 102  * void (*dcd_change)(struct tty_struct *tty, unsigned int status)
 103  *
 104  *      Tells the discipline that the DCD pin has changed its status.
 105  *      Used exclusively by the N_PPS (Pulse-Per-Second) line discipline.
 106  *
 107  * int  (*receive_buf2)(struct tty_struct *, const unsigned char *cp,
 108  *                      char *fp, int count);
 109  *
 110  *      This function is called by the low-level tty driver to send
 111  *      characters received by the hardware to the line discpline for
 112  *      processing.  <cp> is a pointer to the buffer of input
 113  *      character received by the device.  <fp> is a pointer to a
 114  *      pointer of flag bytes which indicate whether a character was
 115  *      received with a parity error, etc. <fp> may be NULL to indicate
 116  *      all data received is TTY_NORMAL.
 117  *      If assigned, prefer this function for automatic flow control.
 118  */
 119
 120 #include <linux/fs.h>
 121 #include <linux/wait.h>
 122
 123
 124 /*
 125  * the semaphore definition
 126  */
 127 struct ld_semaphore {
 128         long                    count;
 129         raw_spinlock_t          wait_lock;
 130         unsigned int            wait_readers;
 131         struct list_head        read_wait;
 132         struct list_head        write_wait;
 133 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 134         struct lockdep_map      dep_map;
 135 #endif
 136 };
 137
 138 extern void __init_ldsem(struct ld_semaphore *sem, const char *name,
 139                          struct lock_class_key *key);
 140
 141 #define init_ldsem(sem)                                         \
 142 do {                                                            \
 143         static struct lock_class_key __key;                     \
 144                                                                 \
 145         __init_ldsem((sem), #sem, &__key);                      \
 146 } while (0)
 147
 148
 149 extern int ldsem_down_read(struct ld_semaphore *sem, long timeout);
 150 extern int ldsem_down_read_trylock(struct ld_semaphore *sem);
 151 extern int ldsem_down_write(struct ld_semaphore *sem, long timeout);
 152 extern int ldsem_down_write_trylock(struct ld_semaphore *sem);
 153 extern void ldsem_up_read(struct ld_semaphore *sem);
 154 extern void ldsem_up_write(struct ld_semaphore *sem);
 155
 156 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 157 extern int ldsem_down_read_nested(struct ld_semaphore *sem, int subclass,
 158                                   long timeout);
 159 extern int ldsem_down_write_nested(struct ld_semaphore *sem, int subclass,
 160                                    long timeout);
 161 #else
 162 # define ldsem_down_read_nested(sem, subclass, timeout)         \
 163                 ldsem_down_read(sem, timeout)
 164 # define ldsem_down_write_nested(sem, subclass, timeout)        \
 165                 ldsem_down_write(sem, timeout)
 166 #endif
 167
 168
 169 struct tty_ldisc_ops {
 170         int     magic;
 171         char    *name;
 172         int     num;
 173         int     flags;
 174
 175         /*
 176          * The following routines are called from above.
 177          */
 178         int     (*open)(struct tty_struct *);
 179         void    (*close)(struct tty_struct *);
 180         void    (*flush_buffer)(struct tty_struct *tty);
 181         ssize_t (*read)(struct tty_struct *tty, struct file *file,
 182                         unsigned char __user *buf, size_t nr);
 183         ssize_t (*write)(struct tty_struct *tty, struct file *file,
 184                          const unsigned char *buf, size_t nr);
 185         int     (*ioctl)(struct tty_struct *tty, struct file *file,
 186                          unsigned int cmd, unsigned long arg);
 187         long    (*compat_ioctl)(struct tty_struct *tty, struct file *file,
 188                                 unsigned int cmd, unsigned long arg);
 189         void    (*set_termios)(struct tty_struct *tty, struct ktermios *old);
 190         unsigned int (*poll)(struct tty_struct *, struct file *,
 191                              struct poll_table_struct *);
 192         int     (*hangup)(struct tty_struct *tty);
 193
 194         /*
 195          * The following routines are called from below.
 196          */
 197         void    (*receive_buf)(struct tty_struct *, const unsigned char *cp,
 198                                char *fp, int count);
 199         void    (*write_wakeup)(struct tty_struct *);
 200         void    (*dcd_change)(struct tty_struct *, unsigned int);
 201         int     (*receive_buf2)(struct tty_struct *, const unsigned char *cp,
 202                                 char *fp, int count);
 203
 204         struct  module *owner;
 205
 206         int refcount;
 207 };
 208
 209 struct tty_ldisc {
 210         struct tty_ldisc_ops *ops;
 211         struct tty_struct *tty;
 212 };
 213
 214 #define TTY_LDISC_MAGIC 0x5403
 215
 216 #define LDISC_FLAG_DEFINED      0x00000001
 217
 218 #define MODULE_ALIAS_LDISC(ldisc) \
 219         MODULE_ALIAS("tty-ldisc-" __stringify(ldisc))
 220
 221 #endif /* _LINUX_TTY_LDISC_H */