include/linux/tty_driver.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef _LINUX_TTY_DRIVER_H
   3 #define _LINUX_TTY_DRIVER_H
   4
   5 /*
   6  * This structure defines the interface between the low-level tty
   7  * driver 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  * struct tty_struct * (*lookup)(struct tty_driver *self, struct file *, int idx)
  12  *
  13  *      Return the tty device corresponding to idx, NULL if there is not
  14  *      one currently in use and an ERR_PTR value on error. Called under
  15  *      tty_mutex (for now!)
  16  *
  17  *      Optional method. Default behaviour is to use the ttys array
  18  *
  19  * int (*install)(struct tty_driver *self, struct tty_struct *tty)
  20  *
  21  *      Install a new tty into the tty driver internal tables. Used in
  22  *      conjunction with lookup and remove methods.
  23  *
  24  *      Optional method. Default behaviour is to use the ttys array
  25  *
  26  * void (*remove)(struct tty_driver *self, struct tty_struct *tty)
  27  *
  28  *      Remove a closed tty from the tty driver internal tables. Used in
  29  *      conjunction with lookup and remove methods.
  30  *
  31  *      Optional method. Default behaviour is to use the ttys array
  32  *
  33  * int  (*open)(struct tty_struct * tty, struct file * filp);
  34  *
  35  *      This routine is called when a particular tty device is opened.
  36  *      This routine is mandatory; if this routine is not filled in,
  37  *      the attempted open will fail with ENODEV.
  38  *
  39  *      Required method. Called with tty lock held.
  40  *
  41  * void (*close)(struct tty_struct * tty, struct file * filp);
  42  *
  43  *      This routine is called when a particular tty device is closed.
  44  *      Note: called even if the corresponding open() failed.
  45  *
  46  *      Required method. Called with tty lock held.
  47  *
  48  * void (*shutdown)(struct tty_struct * tty);
  49  *
  50  *      This routine is called under the tty lock when a particular tty device
  51  *      is closed for the last time. It executes before the tty resources
  52  *      are freed so may execute while another function holds a tty kref.
  53  *
  54  * void (*cleanup)(struct tty_struct * tty);
  55  *
  56  *      This routine is called asynchronously when a particular tty device
  57  *      is closed for the last time freeing up the resources. This is
  58  *      actually the second part of shutdown for routines that might sleep.
  59  *
  60  *
  61  * int (*write)(struct tty_struct * tty,
  62  *               const unsigned char *buf, int count);
  63  *
  64  *      This routine is called by the kernel to write a series of
  65  *      characters to the tty device.  The characters may come from
  66  *      user space or kernel space.  This routine will return the
  67  *      number of characters actually accepted for writing.
  68  *
  69  *      Optional: Required for writable devices.
  70  *
  71  * int (*put_char)(struct tty_struct *tty, unsigned char ch);
  72  *
  73  *      This routine is called by the kernel to write a single
  74  *      character to the tty device.  If the kernel uses this routine,
  75  *      it must call the flush_chars() routine (if defined) when it is
  76  *      done stuffing characters into the driver.  If there is no room
  77  *      in the queue, the character is ignored.
  78  *
  79  *      Optional: Kernel will use the write method if not provided.
  80  *
  81  *      Note: Do not call this function directly, call tty_put_char
  82  *
  83  * void (*flush_chars)(struct tty_struct *tty);
  84  *
  85  *      This routine is called by the kernel after it has written a
  86  *      series of characters to the tty device using put_char().
  87  *
  88  *      Optional:
  89  *
  90  *      Note: Do not call this function directly, call tty_driver_flush_chars
  91  *
  92  * int  (*write_room)(struct tty_struct *tty);
  93  *
  94  *      This routine returns the numbers of characters the tty driver
  95  *      will accept for queuing to be written.  This number is subject
  96  *      to change as output buffers get emptied, or if the output flow
  97  *      control is acted.
  98  *
  99  *      Required if write method is provided else not needed.
 100  *
 101  *      Note: Do not call this function directly, call tty_write_room
 102  *
 103  * int  (*ioctl)(struct tty_struct *tty, unsigned int cmd, unsigned long arg);
 104  *
 105  *      This routine allows the tty driver to implement
 106  *      device-specific ioctls.  If the ioctl number passed in cmd
 107  *      is not recognized by the driver, it should return ENOIOCTLCMD.
 108  *
 109  *      Optional
 110  *
 111  * long (*compat_ioctl)(struct tty_struct *tty,,
 112  *                      unsigned int cmd, unsigned long arg);
 113  *
 114  *      implement ioctl processing for 32 bit process on 64 bit system
 115  *
 116  *      Optional
 117  *
 118  * void (*set_termios)(struct tty_struct *tty, struct ktermios * old);
 119  *
 120  *      This routine allows the tty driver to be notified when
 121  *      device's termios settings have changed.
 122  *
 123  *      Optional: Called under the termios lock
 124  *
 125  *
 126  * void (*set_ldisc)(struct tty_struct *tty);
 127  *
 128  *      This routine allows the tty driver to be notified when the
 129  *      device's termios settings have changed.
 130  *
 131  *      Optional: Called under BKL (currently)
 132  *
 133  * void (*throttle)(struct tty_struct * tty);
 134  *
 135  *      This routine notifies the tty driver that input buffers for
 136  *      the line discipline are close to full, and it should somehow
 137  *      signal that no more characters should be sent to the tty.
 138  *
 139  *      Optional: Always invoke via tty_throttle(), called under the
 140  *      termios lock.
 141  *
 142  * void (*unthrottle)(struct tty_struct * tty);
 143  *
 144  *      This routine notifies the tty drivers that it should signals
 145  *      that characters can now be sent to the tty without fear of
 146  *      overrunning the input buffers of the line disciplines.
 147  *
 148  *      Optional: Always invoke via tty_unthrottle(), called under the
 149  *      termios lock.
 150  *
 151  * void (*stop)(struct tty_struct *tty);
 152  *
 153  *      This routine notifies the tty driver that it should stop
 154  *      outputting characters to the tty device.
 155  *
 156  *      Called with ->flow_lock held. Serialized with start() method.
 157  *
 158  *      Optional:
 159  *
 160  *      Note: Call stop_tty not this method.
 161  *
 162  * void (*start)(struct tty_struct *tty);
 163  *
 164  *      This routine notifies the tty driver that it resume sending
 165  *      characters to the tty device.
 166  *
 167  *      Called with ->flow_lock held. Serialized with stop() method.
 168  *
 169  *      Optional:
 170  *
 171  *      Note: Call start_tty not this method.
 172  *
 173  * void (*hangup)(struct tty_struct *tty);
 174  *
 175  *      This routine notifies the tty driver that it should hang up the
 176  *      tty device.
 177  *
 178  *      Optional:
 179  *
 180  *      Called with tty lock held.
 181  *
 182  * int (*break_ctl)(struct tty_struct *tty, int state);
 183  *
 184  *      This optional routine requests the tty driver to turn on or
 185  *      off BREAK status on the RS-232 port.  If state is -1,
 186  *      then the BREAK status should be turned on; if state is 0, then
 187  *      BREAK should be turned off.
 188  *
 189  *      If this routine is implemented, the high-level tty driver will
 190  *      handle the following ioctls: TCSBRK, TCSBRKP, TIOCSBRK,
 191  *      TIOCCBRK.
 192  *
 193  *      If the driver sets TTY_DRIVER_HARDWARE_BREAK then the interface
 194  *      will also be called with actual times and the hardware is expected
 195  *      to do the delay work itself. 0 and -1 are still used for on/off.
 196  *
 197  *      Optional: Required for TCSBRK/BRKP/etc handling.
 198  *
 199  * void (*wait_until_sent)(struct tty_struct *tty, int timeout);
 200  *
 201  *      This routine waits until the device has written out all of the
 202  *      characters in its transmitter FIFO.
 203  *
 204  *      Optional: If not provided the device is assumed to have no FIFO
 205  *
 206  *      Note: Usually correct to call tty_wait_until_sent
 207  *
 208  * void (*send_xchar)(struct tty_struct *tty, char ch);
 209  *
 210  *      This routine is used to send a high-priority XON/XOFF
 211  *      character to the device.
 212  *
 213  *      Optional: If not provided then the write method is called under
 214  *      the atomic write lock to keep it serialized with the ldisc.
 215  *
 216  * int (*resize)(struct tty_struct *tty, struct winsize *ws)
 217  *
 218  *      Called when a termios request is issued which changes the
 219  *      requested terminal geometry.
 220  *
 221  *      Optional: the default action is to update the termios structure
 222  *      without error. This is usually the correct behaviour. Drivers should
 223  *      not force errors here if they are not resizable objects (eg a serial
 224  *      line). See tty_do_resize() if you need to wrap the standard method
 225  *      in your own logic - the usual case.
 226  *
 227  * void (*set_termiox)(struct tty_struct *tty, struct termiox *new);
 228  *
 229  *      Called when the device receives a termiox based ioctl. Passes down
 230  *      the requested data from user space. This method will not be invoked
 231  *      unless the tty also has a valid tty->termiox pointer.
 232  *
 233  *      Optional: Called under the termios lock
 234  *
 235  * int (*get_icount)(struct tty_struct *tty, struct serial_icounter *icount);
 236  *
 237  *      Called when the device receives a TIOCGICOUNT ioctl. Passed a kernel
 238  *      structure to complete. This method is optional and will only be called
 239  *      if provided (otherwise EINVAL will be returned).
 240  */
 241
 242 #include <linux/export.h>
 243 #include <linux/fs.h>
 244 #include <linux/list.h>
 245 #include <linux/cdev.h>
 246 #include <linux/termios.h>
 247 #include <linux/seq_file.h>
 248
 249 struct tty_struct;
 250 struct tty_driver;
 251 struct serial_icounter_struct;
 252
 253 struct tty_operations {
 254         struct tty_struct * (*lookup)(struct tty_driver *driver,
 255                         struct file *filp, int idx);
 256         int  (*install)(struct tty_driver *driver, struct tty_struct *tty);
 257         void (*remove)(struct tty_driver *driver, struct tty_struct *tty);
 258         int  (*open)(struct tty_struct * tty, struct file * filp);
 259         void (*close)(struct tty_struct * tty, struct file * filp);
 260         void (*shutdown)(struct tty_struct *tty);
 261         void (*cleanup)(struct tty_struct *tty);
 262         int  (*write)(struct tty_struct * tty,
 263                       const unsigned char *buf, int count);
 264         int  (*put_char)(struct tty_struct *tty, unsigned char ch);
 265         void (*flush_chars)(struct tty_struct *tty);
 266         int  (*write_room)(struct tty_struct *tty);
 267         int  (*chars_in_buffer)(struct tty_struct *tty);
 268         int  (*ioctl)(struct tty_struct *tty,
 269                     unsigned int cmd, unsigned long arg);
 270         long (*compat_ioctl)(struct tty_struct *tty,
 271                              unsigned int cmd, unsigned long arg);
 272         void (*set_termios)(struct tty_struct *tty, struct ktermios * old);
 273         void (*throttle)(struct tty_struct * tty);
 274         void (*unthrottle)(struct tty_struct * tty);
 275         void (*stop)(struct tty_struct *tty);
 276         void (*start)(struct tty_struct *tty);
 277         void (*hangup)(struct tty_struct *tty);
 278         int (*break_ctl)(struct tty_struct *tty, int state);
 279         void (*flush_buffer)(struct tty_struct *tty);
 280         void (*set_ldisc)(struct tty_struct *tty);
 281         void (*wait_until_sent)(struct tty_struct *tty, int timeout);
 282         void (*send_xchar)(struct tty_struct *tty, char ch);
 283         int (*tiocmget)(struct tty_struct *tty);
 284         int (*tiocmset)(struct tty_struct *tty,
 285                         unsigned int set, unsigned int clear);
 286         int (*resize)(struct tty_struct *tty, struct winsize *ws);
 287         int (*set_termiox)(struct tty_struct *tty, struct termiox *tnew);
 288         int (*get_icount)(struct tty_struct *tty,
 289                                 struct serial_icounter_struct *icount);
 290         void (*show_fdinfo)(struct tty_struct *tty, struct seq_file *m);
 291 #ifdef CONFIG_CONSOLE_POLL
 292         int (*poll_init)(struct tty_driver *driver, int line, char *options);
 293         int (*poll_get_char)(struct tty_driver *driver, int line);
 294         void (*poll_put_char)(struct tty_driver *driver, int line, char ch);
 295 #endif
 296         const struct file_operations *proc_fops;
 297 } __randomize_layout;
 298
 299 struct tty_driver {
 300         int     magic;          /* magic number for this structure */
 301         struct kref kref;       /* Reference management */
 302         struct cdev **cdevs;
 303         struct module   *owner;
 304         const char      *driver_name;
 305         const char      *name;
 306         int     name_base;      /* offset of printed name */
 307         int     major;          /* major device number */
 308         int     minor_start;    /* start of minor device number */
 309         unsigned int    num;    /* number of devices allocated */
 310         short   type;           /* type of tty driver */
 311         short   subtype;        /* subtype of tty driver */
 312         struct ktermios init_termios; /* Initial termios */
 313         unsigned long   flags;          /* tty driver flags */
 314         struct proc_dir_entry *proc_entry; /* /proc fs entry */
 315         struct tty_driver *other; /* only used for the PTY driver */
 316
 317         /*
 318          * Pointer to the tty data structures
 319          */
 320         struct tty_struct **ttys;
 321         struct tty_port **ports;
 322         struct ktermios **termios;
 323         void *driver_state;
 324
 325         /*
 326          * Driver methods
 327          */
 328
 329         const struct tty_operations *ops;
 330         struct list_head tty_drivers;
 331 } __randomize_layout;
 332
 333 extern struct list_head tty_drivers;
 334
 335 extern struct tty_driver *__tty_alloc_driver(unsigned int lines,
 336                 struct module *owner, unsigned long flags);
 337 extern void put_tty_driver(struct tty_driver *driver);
 338 extern void tty_set_operations(struct tty_driver *driver,
 339                         const struct tty_operations *op);
 340 extern struct tty_driver *tty_find_polling_driver(char *name, int *line);
 341
 342 extern void tty_driver_kref_put(struct tty_driver *driver);
 343
 344 /* Use TTY_DRIVER_* flags below */
 345 #define tty_alloc_driver(lines, flags) \
 346                 __tty_alloc_driver(lines, THIS_MODULE, flags)
 347
 348 /*
 349  * DEPRECATED Do not use this in new code, use tty_alloc_driver instead.
 350  * (And change the return value checks.)
 351  */
 352 static inline struct tty_driver *alloc_tty_driver(unsigned int lines)
 353 {
 354         struct tty_driver *ret = tty_alloc_driver(lines, 0);
 355         if (IS_ERR(ret))
 356                 return NULL;
 357         return ret;
 358 }
 359
 360 static inline struct tty_driver *tty_driver_kref_get(struct tty_driver *d)
 361 {
 362         kref_get(&d->kref);
 363         return d;
 364 }
 365
 366 /* tty driver magic number */
 367 #define TTY_DRIVER_MAGIC                0x5402
 368
 369 /*
 370  * tty driver flags
 371  *
 372  * TTY_DRIVER_RESET_TERMIOS --- requests the tty layer to reset the
 373  *      termios setting when the last process has closed the device.
 374  *      Used for PTY's, in particular.
 375  *
 376  * TTY_DRIVER_REAL_RAW --- if set, indicates that the driver will
 377  *      guarantee never not to set any special character handling
 378  *      flags if ((IGNBRK || (!BRKINT && !PARMRK)) && (IGNPAR ||
 379  *      !INPCK)).  That is, if there is no reason for the driver to
 380  *      send notifications of parity and break characters up to the
 381  *      line driver, it won't do so.  This allows the line driver to
 382  *      optimize for this case if this flag is set.  (Note that there
 383  *      is also a promise, if the above case is true, not to signal
 384  *      overruns, either.)
 385  *
 386  * TTY_DRIVER_DYNAMIC_DEV --- if set, the individual tty devices need
 387  *      to be registered with a call to tty_register_device() when the
 388  *      device is found in the system and unregistered with a call to
 389  *      tty_unregister_device() so the devices will be show up
 390  *      properly in sysfs.  If not set, driver->num entries will be
 391  *      created by the tty core in sysfs when tty_register_driver() is
 392  *      called.  This is to be used by drivers that have tty devices
 393  *      that can appear and disappear while the main tty driver is
 394  *      registered with the tty core.
 395  *
 396  * TTY_DRIVER_DEVPTS_MEM -- don't use the standard arrays, instead
 397  *      use dynamic memory keyed through the devpts filesystem.  This
 398  *      is only applicable to the pty driver.
 399  *
 400  * TTY_DRIVER_HARDWARE_BREAK -- hardware handles break signals. Pass
 401  *      the requested timeout to the caller instead of using a simple
 402  *      on/off interface.
 403  *
 404  * TTY_DRIVER_DYNAMIC_ALLOC -- do not allocate structures which are
 405  *      needed per line for this driver as it would waste memory.
 406  *      The driver will take care.
 407  *
 408  * TTY_DRIVER_UNNUMBERED_NODE -- do not create numbered /dev nodes. In
 409  *      other words create /dev/ttyprintk and not /dev/ttyprintk0.
 410  *      Applicable only when a driver for a single tty device is
 411  *      being allocated.
 412  */
 413 #define TTY_DRIVER_INSTALLED            0x0001
 414 #define TTY_DRIVER_RESET_TERMIOS        0x0002
 415 #define TTY_DRIVER_REAL_RAW             0x0004
 416 #define TTY_DRIVER_DYNAMIC_DEV          0x0008
 417 #define TTY_DRIVER_DEVPTS_MEM           0x0010
 418 #define TTY_DRIVER_HARDWARE_BREAK       0x0020
 419 #define TTY_DRIVER_DYNAMIC_ALLOC        0x0040
 420 #define TTY_DRIVER_UNNUMBERED_NODE      0x0080
 421
 422 /* tty driver types */
 423 #define TTY_DRIVER_TYPE_SYSTEM          0x0001
 424 #define TTY_DRIVER_TYPE_CONSOLE         0x0002
 425 #define TTY_DRIVER_TYPE_SERIAL          0x0003
 426 #define TTY_DRIVER_TYPE_PTY             0x0004
 427 #define TTY_DRIVER_TYPE_SCC             0x0005  /* scc driver */
 428 #define TTY_DRIVER_TYPE_SYSCONS         0x0006
 429
 430 /* system subtypes (magic, used by tty_io.c) */
 431 #define SYSTEM_TYPE_TTY                 0x0001
 432 #define SYSTEM_TYPE_CONSOLE             0x0002
 433 #define SYSTEM_TYPE_SYSCONS             0x0003
 434 #define SYSTEM_TYPE_SYSPTMX             0x0004
 435
 436 /* pty subtypes (magic, used by tty_io.c) */
 437 #define PTY_TYPE_MASTER                 0x0001
 438 #define PTY_TYPE_SLAVE                  0x0002
 439
 440 /* serial subtype definitions */
 441 #define SERIAL_TYPE_NORMAL      1
 442
 443 #endif /* #ifdef _LINUX_TTY_DRIVER_H */