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  * unsigned 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_safe(), 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  * int (*get_icount)(struct tty_struct *tty, struct serial_icounter *icount);
 228  *
 229  *      Called when the device receives a TIOCGICOUNT ioctl. Passed a kernel
 230  *      structure to complete. This method is optional and will only be called
 231  *      if provided (otherwise ENOTTY will be returned).
 232  */
 233
 234 #include <linux/export.h>
 235 #include <linux/fs.h>
 236 #include <linux/kref.h>
 237 #include <linux/list.h>
 238 #include <linux/cdev.h>
 239 #include <linux/termios.h>
 240 #include <linux/seq_file.h>
 241
 242 struct tty_struct;
 243 struct tty_driver;
 244 struct serial_icounter_struct;
 245 struct serial_struct;
 246
 247 struct tty_operations {
 248         struct tty_struct * (*lookup)(struct tty_driver *driver,
 249                         struct file *filp, int idx);
 250         int  (*install)(struct tty_driver *driver, struct tty_struct *tty);
 251         void (*remove)(struct tty_driver *driver, struct tty_struct *tty);
 252         int  (*open)(struct tty_struct * tty, struct file * filp);
 253         void (*close)(struct tty_struct * tty, struct file * filp);
 254         void (*shutdown)(struct tty_struct *tty);
 255         void (*cleanup)(struct tty_struct *tty);
 256         int  (*write)(struct tty_struct * tty,
 257                       const unsigned char *buf, int count);
 258         int  (*put_char)(struct tty_struct *tty, unsigned char ch);
 259         void (*flush_chars)(struct tty_struct *tty);
 260         unsigned int (*write_room)(struct tty_struct *tty);
 261         unsigned int (*chars_in_buffer)(struct tty_struct *tty);
 262         int  (*ioctl)(struct tty_struct *tty,
 263                     unsigned int cmd, unsigned long arg);
 264         long (*compat_ioctl)(struct tty_struct *tty,
 265                              unsigned int cmd, unsigned long arg);
 266         void (*set_termios)(struct tty_struct *tty, struct ktermios * old);
 267         void (*throttle)(struct tty_struct * tty);
 268         void (*unthrottle)(struct tty_struct * tty);
 269         void (*stop)(struct tty_struct *tty);
 270         void (*start)(struct tty_struct *tty);
 271         void (*hangup)(struct tty_struct *tty);
 272         int (*break_ctl)(struct tty_struct *tty, int state);
 273         void (*flush_buffer)(struct tty_struct *tty);
 274         void (*set_ldisc)(struct tty_struct *tty);
 275         void (*wait_until_sent)(struct tty_struct *tty, int timeout);
 276         void (*send_xchar)(struct tty_struct *tty, char ch);
 277         int (*tiocmget)(struct tty_struct *tty);
 278         int (*tiocmset)(struct tty_struct *tty,
 279                         unsigned int set, unsigned int clear);
 280         int (*resize)(struct tty_struct *tty, struct winsize *ws);
 281         int (*get_icount)(struct tty_struct *tty,
 282                                 struct serial_icounter_struct *icount);
 283         int  (*get_serial)(struct tty_struct *tty, struct serial_struct *p);
 284         int  (*set_serial)(struct tty_struct *tty, struct serial_struct *p);
 285         void (*show_fdinfo)(struct tty_struct *tty, struct seq_file *m);
 286 #ifdef CONFIG_CONSOLE_POLL
 287         int (*poll_init)(struct tty_driver *driver, int line, char *options);
 288         int (*poll_get_char)(struct tty_driver *driver, int line);
 289         void (*poll_put_char)(struct tty_driver *driver, int line, char ch);
 290 #endif
 291         int (*proc_show)(struct seq_file *, void *);
 292 } __randomize_layout;
 293
 294 struct tty_driver {
 295         int     magic;          /* magic number for this structure */
 296         struct kref kref;       /* Reference management */
 297         struct cdev **cdevs;
 298         struct module   *owner;
 299         const char      *driver_name;
 300         const char      *name;
 301         int     name_base;      /* offset of printed name */
 302         int     major;          /* major device number */
 303         int     minor_start;    /* start of minor device number */
 304         unsigned int    num;    /* number of devices allocated */
 305         short   type;           /* type of tty driver */
 306         short   subtype;        /* subtype of tty driver */
 307         struct ktermios init_termios; /* Initial termios */
 308         unsigned long   flags;          /* tty driver flags */
 309         struct proc_dir_entry *proc_entry; /* /proc fs entry */
 310         struct tty_driver *other; /* only used for the PTY driver */
 311
 312         /*
 313          * Pointer to the tty data structures
 314          */
 315         struct tty_struct **ttys;
 316         struct tty_port **ports;
 317         struct ktermios **termios;
 318         void *driver_state;
 319
 320         /*
 321          * Driver methods
 322          */
 323
 324         const struct tty_operations *ops;
 325         struct list_head tty_drivers;
 326 } __randomize_layout;
 327
 328 extern struct list_head tty_drivers;
 329
 330 extern struct tty_driver *__tty_alloc_driver(unsigned int lines,
 331                 struct module *owner, unsigned long flags);
 332 extern struct tty_driver *tty_find_polling_driver(char *name, int *line);
 333
 334 extern void tty_driver_kref_put(struct tty_driver *driver);
 335
 336 /* Use TTY_DRIVER_* flags below */
 337 #define tty_alloc_driver(lines, flags) \
 338                 __tty_alloc_driver(lines, THIS_MODULE, flags)
 339
 340 static inline struct tty_driver *tty_driver_kref_get(struct tty_driver *d)
 341 {
 342         kref_get(&d->kref);
 343         return d;
 344 }
 345
 346 static inline void tty_set_operations(struct tty_driver *driver,
 347                 const struct tty_operations *op)
 348 {
 349         driver->ops = op;
 350 }
 351
 352 /* tty driver magic number */
 353 #define TTY_DRIVER_MAGIC                0x5402
 354
 355 /*
 356  * tty driver flags
 357  *
 358  * TTY_DRIVER_RESET_TERMIOS --- requests the tty layer to reset the
 359  *      termios setting when the last process has closed the device.
 360  *      Used for PTY's, in particular.
 361  *
 362  * TTY_DRIVER_REAL_RAW --- if set, indicates that the driver will
 363  *      guarantee never not to set any special character handling
 364  *      flags if ((IGNBRK || (!BRKINT && !PARMRK)) && (IGNPAR ||
 365  *      !INPCK)).  That is, if there is no reason for the driver to
 366  *      send notifications of parity and break characters up to the
 367  *      line driver, it won't do so.  This allows the line driver to
 368  *      optimize for this case if this flag is set.  (Note that there
 369  *      is also a promise, if the above case is true, not to signal
 370  *      overruns, either.)
 371  *
 372  * TTY_DRIVER_DYNAMIC_DEV --- if set, the individual tty devices need
 373  *      to be registered with a call to tty_register_device() when the
 374  *      device is found in the system and unregistered with a call to
 375  *      tty_unregister_device() so the devices will be show up
 376  *      properly in sysfs.  If not set, driver->num entries will be
 377  *      created by the tty core in sysfs when tty_register_driver() is
 378  *      called.  This is to be used by drivers that have tty devices
 379  *      that can appear and disappear while the main tty driver is
 380  *      registered with the tty core.
 381  *
 382  * TTY_DRIVER_DEVPTS_MEM -- don't use the standard arrays, instead
 383  *      use dynamic memory keyed through the devpts filesystem.  This
 384  *      is only applicable to the pty driver.
 385  *
 386  * TTY_DRIVER_HARDWARE_BREAK -- hardware handles break signals. Pass
 387  *      the requested timeout to the caller instead of using a simple
 388  *      on/off interface.
 389  *
 390  * TTY_DRIVER_DYNAMIC_ALLOC -- do not allocate structures which are
 391  *      needed per line for this driver as it would waste memory.
 392  *      The driver will take care.
 393  *
 394  * TTY_DRIVER_UNNUMBERED_NODE -- do not create numbered /dev nodes. In
 395  *      other words create /dev/ttyprintk and not /dev/ttyprintk0.
 396  *      Applicable only when a driver for a single tty device is
 397  *      being allocated.
 398  */
 399 #define TTY_DRIVER_INSTALLED            0x0001
 400 #define TTY_DRIVER_RESET_TERMIOS        0x0002
 401 #define TTY_DRIVER_REAL_RAW             0x0004
 402 #define TTY_DRIVER_DYNAMIC_DEV          0x0008
 403 #define TTY_DRIVER_DEVPTS_MEM           0x0010
 404 #define TTY_DRIVER_HARDWARE_BREAK       0x0020
 405 #define TTY_DRIVER_DYNAMIC_ALLOC        0x0040
 406 #define TTY_DRIVER_UNNUMBERED_NODE      0x0080
 407
 408 /* tty driver types */
 409 #define TTY_DRIVER_TYPE_SYSTEM          0x0001
 410 #define TTY_DRIVER_TYPE_CONSOLE         0x0002
 411 #define TTY_DRIVER_TYPE_SERIAL          0x0003
 412 #define TTY_DRIVER_TYPE_PTY             0x0004
 413 #define TTY_DRIVER_TYPE_SCC             0x0005  /* scc driver */
 414 #define TTY_DRIVER_TYPE_SYSCONS         0x0006
 415
 416 /* system subtypes (magic, used by tty_io.c) */
 417 #define SYSTEM_TYPE_TTY                 0x0001
 418 #define SYSTEM_TYPE_CONSOLE             0x0002
 419 #define SYSTEM_TYPE_SYSCONS             0x0003
 420 #define SYSTEM_TYPE_SYSPTMX             0x0004
 421
 422 /* pty subtypes (magic, used by tty_io.c) */
 423 #define PTY_TYPE_MASTER                 0x0001
 424 #define PTY_TYPE_SLAVE                  0x0002
 425
 426 /* serial subtype definitions */
 427 #define SERIAL_TYPE_NORMAL      1
 428
 429 int tty_register_driver(struct tty_driver *driver);
 430 void tty_unregister_driver(struct tty_driver *driver);
 431 struct device *tty_register_device(struct tty_driver *driver, unsigned index,
 432                 struct device *dev);
 433 struct device *tty_register_device_attr(struct tty_driver *driver,
 434                 unsigned index, struct device *device, void *drvdata,
 435                 const struct attribute_group **attr_grp);
 436 void tty_unregister_device(struct tty_driver *driver, unsigned index);
 437
 438 #ifdef CONFIG_PROC_FS
 439 void proc_tty_register_driver(struct tty_driver *);
 440 void proc_tty_unregister_driver(struct tty_driver *);
 441 #else
 442 static inline void proc_tty_register_driver(struct tty_driver *d) {}
 443 static inline void proc_tty_unregister_driver(struct tty_driver *d) {}
 444 #endif
 445
 446 #endif /* #ifdef _LINUX_TTY_DRIVER_H */