/* SPDX-License-Identifier: GPL-2.0 */ #ifndef _LINUX_TTY_DRIVER_H #define _LINUX_TTY_DRIVER_H #include <linux/export.h> #include <linux/fs.h> #include <linux/kref.h> #include <linux/list.h> #include <linux/cdev.h> #include <linux/uaccess.h> #include <linux/termios.h> #include <linux/seq_file.h> struct tty_struct; struct tty_driver; struct serial_icounter_struct; struct serial_struct; /** * struct tty_operations -- interface between driver and tty * * @lookup: ``struct tty_struct *()(struct tty_driver *self, struct file *, * int idx)`` * * Return the tty device corresponding to @idx, %NULL if there is not * one currently in use and an %ERR_PTR value on error. Called under * %tty_mutex (for now!) * * Optional method. Default behaviour is to use the @self->ttys array. * * @install: ``int ()(struct tty_driver *self, struct tty_struct *tty)`` * * Install a new @tty into the @self's internal tables. Used in * conjunction with @lookup and @remove methods. * * Optional method. Default behaviour is to use the @self->ttys array. * * @remove: ``void ()(struct tty_driver *self, struct tty_struct *tty)`` * * Remove a closed @tty from the @self's internal tables. Used in * conjunction with @lookup and @remove methods. * * Optional method. Default behaviour is to use the @self->ttys array. * * @open: ``int ()(struct tty_struct *tty, struct file *)`` * * This routine is called when a particular @tty device is opened. This * routine is mandatory; if this routine is not filled in, the attempted * open will fail with %ENODEV. * * Required method. Called with tty lock held. May sleep. * * @close: ``void ()(struct tty_struct *tty, struct file *)`` * * This routine is called when a particular @tty device is closed. At the * point of return from this call the driver must make no further ldisc * calls of any kind. * * Remark: called even if the corresponding @open() failed. * * Required method. Called with tty lock held. May sleep. * * @shutdown: ``void ()(struct tty_struct *tty)`` * * This routine is called under the tty lock when a particular @tty device * is closed for the last time. It executes before the @tty resources * are freed so may execute while another function holds a @tty kref. * * @cleanup: ``void ()(struct tty_struct *tty)`` * * This routine is called asynchronously when a particular @tty device * is closed for the last time freeing up the resources. This is * actually the second part of shutdown for routines that might sleep. * * @write: ``ssize_t ()(struct tty_struct *tty, const u8 *buf, size_t count)`` * * This routine is called by the kernel to write a series (@count) of * characters (@buf) to the @tty device. The characters may come from * user space or kernel space. This routine will return the * number of characters actually accepted for writing. * * May occur in parallel in special cases. Because this includes panic * paths drivers generally shouldn't try and do clever locking here. * * Optional: Required for writable devices. May not sleep. * * @put_char: ``int ()(struct tty_struct *tty, u8 ch)`` * * This routine is called by the kernel to write a single character @ch to * the @tty device. If the kernel uses this routine, it must call the * @flush_chars() routine (if defined) when it is done stuffing characters * into the driver. If there is no room in the queue, the character is * ignored. * * Optional: Kernel will use the @write method if not provided. Do not * call this function directly, call tty_put_char(). * * @flush_chars: ``void ()(struct tty_struct *tty)`` * * This routine is called by the kernel after it has written a * series of characters to the tty device using @put_char(). * * Optional. Do not call this function directly, call * tty_driver_flush_chars(). * * @write_room: ``unsigned int ()(struct tty_struct *tty)`` * * This routine returns the numbers of characters the @tty driver * will accept for queuing to be written. This number is subject * to change as output buffers get emptied, or if the output flow * control is acted. * * The ldisc is responsible for being intelligent about multi-threading of * write_room/write calls * * Required if @write method is provided else not needed. Do not call this * function directly, call tty_write_room() * * @chars_in_buffer: ``unsigned int ()(struct tty_struct *tty)`` * * This routine returns the number of characters in the device private * output queue. Used in tty_wait_until_sent() and for poll() * implementation. * * Optional: if not provided, it is assumed there is no queue on the * device. Do not call this function directly, call tty_chars_in_buffer(). * * @ioctl: ``int ()(struct tty_struct *tty, unsigned int cmd, * unsigned long arg)`` * * This routine allows the @tty driver to implement device-specific * ioctls. If the ioctl number passed in @cmd is not recognized by the * driver, it should return %ENOIOCTLCMD. * * Optional. * * @compat_ioctl: ``long ()(struct tty_struct *tty, unsigned int cmd, * unsigned long arg)`` * * Implement ioctl processing for 32 bit process on 64 bit system. * * Optional. * * @set_termios: ``void ()(struct tty_struct *tty, const struct ktermios *old)`` * * This routine allows the @tty driver to be notified when device's * termios settings have changed. New settings are in @tty->termios. * Previous settings are passed in the @old argument. * * The API is defined such that the driver should return the actual modes * selected. This means that the driver is responsible for modifying any * bits in @tty->termios it cannot fulfill to indicate the actual modes * being used. * * Optional. Called under the @tty->termios_rwsem. May sleep. * * @ldisc_ok: ``int ()(struct tty_struct *tty, int ldisc)`` * * This routine allows the @tty driver to decide if it can deal * with a particular @ldisc. * * Optional. Called under the @tty->ldisc_sem and @tty->termios_rwsem. * * @set_ldisc: ``void ()(struct tty_struct *tty)`` * * This routine allows the @tty driver to be notified when the device's * line discipline is being changed. At the point this is done the * discipline is not yet usable. * * Optional. Called under the @tty->ldisc_sem and @tty->termios_rwsem. * * @throttle: ``void ()(struct tty_struct *tty)`` * * This routine notifies the @tty driver that input buffers for the line * discipline are close to full, and it should somehow signal that no more * characters should be sent to the @tty. * * Serialization including with @unthrottle() is the job of the ldisc * layer. * * Optional: Always invoke via tty_throttle_safe(). Called under the * @tty->termios_rwsem. * * @unthrottle: ``void ()(struct tty_struct *tty)`` * * This routine notifies the @tty driver that it should signal that * characters can now be sent to the @tty without fear of overrunning the * input buffers of the line disciplines. * * Optional. Always invoke via tty_unthrottle(). Called under the * @tty->termios_rwsem. * * @stop: ``void ()(struct tty_struct *tty)`` * * This routine notifies the @tty driver that it should stop outputting * characters to the tty device. * * Called with @tty->flow.lock held. Serialized with @start() method. * * Optional. Always invoke via stop_tty(). * * @start: ``void ()(struct tty_struct *tty)`` * * This routine notifies the @tty driver that it resumed sending * characters to the @tty device. * * Called with @tty->flow.lock held. Serialized with stop() method. * * Optional. Always invoke via start_tty(). * * @hangup: ``void ()(struct tty_struct *tty)`` * * This routine notifies the @tty driver that it should hang up the @tty * device. * * Optional. Called with tty lock held. * * @break_ctl: ``int ()(struct tty_struct *tty, int state)`` * * This optional routine requests the @tty driver to turn on or off BREAK * status on the RS-232 port. If @state is -1, then the BREAK status * should be turned on; if @state is 0, then BREAK should be turned off. * * If this routine is implemented, the high-level tty driver will handle * the following ioctls: %TCSBRK, %TCSBRKP, %TIOCSBRK, %TIOCCBRK. * * If the driver sets %TTY_DRIVER_HARDWARE_BREAK in tty_alloc_driver(), * then the interface will also be called with actual times and the * hardware is expected to do the delay work itself. 0 and -1 are still * used for on/off. * * Optional: Required for %TCSBRK/%BRKP/etc. handling. May sleep. * * @flush_buffer: ``void ()(struct tty_struct *tty)`` * * This routine discards device private output buffer. Invoked on close, * hangup, to implement %TCOFLUSH ioctl and similar. * * Optional: if not provided, it is assumed there is no queue on the * device. Do not call this function directly, call * tty_driver_flush_buffer(). * * @wait_until_sent: ``void ()(struct tty_struct *tty, int timeout)`` * * This routine waits until the device has written out all of the * characters in its transmitter FIFO. Or until @timeout (in jiffies) is * reached. * * Optional: If not provided, the device is assumed to have no FIFO. * Usually correct to invoke via tty_wait_until_sent(). May sleep. * * @send_xchar: ``void ()(struct tty_struct *tty, u8 ch)`` * * This routine is used to send a high-priority XON/XOFF character (@ch) * to the @tty device. * * Optional: If not provided, then the @write method is called under * the @tty->atomic_write_lock to keep it serialized with the ldisc. * * @tiocmget: ``int ()(struct tty_struct *tty)`` * * This routine is used to obtain the modem status bits from the @tty * driver. * * Optional: If not provided, then %ENOTTY is returned from the %TIOCMGET * ioctl. Do not call this function directly, call tty_tiocmget(). * * @tiocmset: ``int ()(struct tty_struct *tty, * unsigned int set, unsigned int clear)`` * * This routine is used to set the modem status bits to the @tty driver. * First, @clear bits should be cleared, then @set bits set. * * Optional: If not provided, then %ENOTTY is returned from the %TIOCMSET * ioctl. Do not call this function directly, call tty_tiocmset(). * * @resize: ``int ()(struct tty_struct *tty, struct winsize *ws)`` * * Called when a termios request is issued which changes the requested * terminal geometry to @ws. * * Optional: the default action is to update the termios structure * without error. This is usually the correct behaviour. Drivers should * not force errors here if they are not resizable objects (e.g. a serial * line). See tty_do_resize() if you need to wrap the standard method * in your own logic -- the usual case. * * @get_icount: ``int ()(struct tty_struct *tty, * struct serial_icounter *icount)`` * * Called when the @tty device receives a %TIOCGICOUNT ioctl. Passed a * kernel structure @icount to complete. * * Optional: called only if provided, otherwise %ENOTTY will be returned. * * @get_serial: ``int ()(struct tty_struct *tty, struct serial_struct *p)`` * * Called when the @tty device receives a %TIOCGSERIAL ioctl. Passed a * kernel structure @p (&struct serial_struct) to complete. * * Optional: called only if provided, otherwise %ENOTTY will be returned. * Do not call this function directly, call tty_tiocgserial(). * * @set_serial: ``int ()(struct tty_struct *tty, struct serial_struct *p)`` * * Called when the @tty device receives a %TIOCSSERIAL ioctl. Passed a * kernel structure @p (&struct serial_struct) to set the values from. * * Optional: called only if provided, otherwise %ENOTTY will be returned. * Do not call this function directly, call tty_tiocsserial(). * * @show_fdinfo: ``void ()(struct tty_struct *tty, struct seq_file *m)`` * * Called when the @tty device file descriptor receives a fdinfo request * from VFS (to show in /proc/<pid>/fdinfo/). @m should be filled with * information. * * Optional: called only if provided, otherwise nothing is written to @m. * Do not call this function directly, call tty_show_fdinfo(). * * @poll_init: ``int ()(struct tty_driver *driver, int line, char *options)`` * * kgdboc support (Documentation/dev-tools/kgdb.rst). This routine is * called to initialize the HW for later use by calling @poll_get_char or * @poll_put_char. * * Optional: called only if provided, otherwise skipped as a non-polling * driver. * * @poll_get_char: ``int ()(struct tty_driver *driver, int line)`` * * kgdboc support (see @poll_init). @driver should read a character from a * tty identified by @line and return it. * * Optional: called only if @poll_init provided. * * @poll_put_char: ``void ()(struct tty_driver *driver, int line, char ch)`` * * kgdboc support (see @poll_init). @driver should write character @ch to * a tty identified by @line. * * Optional: called only if @poll_init provided. * * @proc_show: ``int ()(struct seq_file *m, void *driver)`` * * Driver @driver (cast to &struct tty_driver) can show additional info in * /proc/tty/driver/<driver_name>. It is enough to fill in the information * into @m. * * Optional: called only if provided, otherwise no /proc entry created. * * This structure defines the interface between the low-level tty driver and * the tty routines. These routines can be defined. Unless noted otherwise, * they are optional, and can be filled in with a %NULL pointer. */ struct tty_operations { … } __randomize_layout; /** * struct tty_driver -- driver for TTY devices * * @kref: reference counting. Reaching zero frees all the internals and the * driver. * @cdevs: allocated/registered character /dev devices * @owner: modules owning this driver. Used drivers cannot be rmmod'ed. * Automatically set by tty_alloc_driver(). * @driver_name: name of the driver used in /proc/tty * @name: used for constructing /dev node name * @name_base: used as a number base for constructing /dev node name * @major: major /dev device number (zero for autoassignment) * @minor_start: the first minor /dev device number * @num: number of devices allocated * @type: type of tty driver (%TTY_DRIVER_TYPE_) * @subtype: subtype of tty driver (%SYSTEM_TYPE_, %PTY_TYPE_, %SERIAL_TYPE_) * @init_termios: termios to set to each tty initially (e.g. %tty_std_termios) * @flags: tty driver flags (%TTY_DRIVER_) * @proc_entry: proc fs entry, used internally * @other: driver of the linked tty; only used for the PTY driver * @ttys: array of active &struct tty_struct, set by tty_standard_install() * @ports: array of &struct tty_port; can be set during initialization by * tty_port_link_device() and similar * @termios: storage for termios at each TTY close for the next open * @driver_state: pointer to driver's arbitrary data * @ops: driver hooks for TTYs. Set them using tty_set_operations(). Use &struct * tty_port helpers in them as much as possible. * @tty_drivers: used internally to link tty_drivers together * * The usual handling of &struct tty_driver is to allocate it by * tty_alloc_driver(), set up all the necessary members, and register it by * tty_register_driver(). At last, the driver is torn down by calling * tty_unregister_driver() followed by tty_driver_kref_put(). * * The fields required to be set before calling tty_register_driver() include * @driver_name, @name, @type, @subtype, @init_termios, and @ops. */ struct tty_driver { … } __randomize_layout; extern struct list_head tty_drivers; struct tty_driver *__tty_alloc_driver(unsigned int lines, struct module *owner, unsigned long flags); struct tty_driver *tty_find_polling_driver(char *name, int *line); void tty_driver_kref_put(struct tty_driver *driver); /* Use TTY_DRIVER_* flags below */ #define tty_alloc_driver(lines, flags) … static inline struct tty_driver *tty_driver_kref_get(struct tty_driver *d) { … } static inline void tty_set_operations(struct tty_driver *driver, const struct tty_operations *op) { … } /** * DOC: TTY Driver Flags * * TTY_DRIVER_RESET_TERMIOS * Requests the tty layer to reset the termios setting when the last * process has closed the device. Used for PTYs, in particular. * * TTY_DRIVER_REAL_RAW * Indicates that the driver will guarantee not to set any special * character handling flags if this is set for the tty: * * ``(IGNBRK || (!BRKINT && !PARMRK)) && (IGNPAR || !INPCK)`` * * That is, if there is no reason for the driver to * send notifications of parity and break characters up to the line * driver, it won't do so. This allows the line driver to optimize for * this case if this flag is set. (Note that there is also a promise, if * the above case is true, not to signal overruns, either.) * * TTY_DRIVER_DYNAMIC_DEV * The individual tty devices need to be registered with a call to * tty_register_device() when the device is found in the system and * unregistered with a call to tty_unregister_device() so the devices will * be show up properly in sysfs. If not set, all &tty_driver.num entries * will be created by the tty core in sysfs when tty_register_driver() is * called. This is to be used by drivers that have tty devices that can * appear and disappear while the main tty driver is registered with the * tty core. * * TTY_DRIVER_DEVPTS_MEM * Don't use the standard arrays (&tty_driver.ttys and * &tty_driver.termios), instead use dynamic memory keyed through the * devpts filesystem. This is only applicable to the PTY driver. * * TTY_DRIVER_HARDWARE_BREAK * Hardware handles break signals. Pass the requested timeout to the * &tty_operations.break_ctl instead of using a simple on/off interface. * * TTY_DRIVER_DYNAMIC_ALLOC * Do not allocate structures which are needed per line for this driver * (&tty_driver.ports) as it would waste memory. The driver will take * care. This is only applicable to the PTY driver. * * TTY_DRIVER_UNNUMBERED_NODE * Do not create numbered ``/dev`` nodes. For example, create * ``/dev/ttyprintk`` and not ``/dev/ttyprintk0``. Applicable only when a * driver for a single tty device is being allocated. */ #define TTY_DRIVER_INSTALLED … #define TTY_DRIVER_RESET_TERMIOS … #define TTY_DRIVER_REAL_RAW … #define TTY_DRIVER_DYNAMIC_DEV … #define TTY_DRIVER_DEVPTS_MEM … #define TTY_DRIVER_HARDWARE_BREAK … #define TTY_DRIVER_DYNAMIC_ALLOC … #define TTY_DRIVER_UNNUMBERED_NODE … /* tty driver types */ #define TTY_DRIVER_TYPE_SYSTEM … #define TTY_DRIVER_TYPE_CONSOLE … #define TTY_DRIVER_TYPE_SERIAL … #define TTY_DRIVER_TYPE_PTY … #define TTY_DRIVER_TYPE_SCC … #define TTY_DRIVER_TYPE_SYSCONS … /* system subtypes (magic, used by tty_io.c) */ #define SYSTEM_TYPE_TTY … #define SYSTEM_TYPE_CONSOLE … #define SYSTEM_TYPE_SYSCONS … #define SYSTEM_TYPE_SYSPTMX … /* pty subtypes (magic, used by tty_io.c) */ #define PTY_TYPE_MASTER … #define PTY_TYPE_SLAVE … /* serial subtype definitions */ #define SERIAL_TYPE_NORMAL … int tty_register_driver(struct tty_driver *driver); void tty_unregister_driver(struct tty_driver *driver); struct device *tty_register_device(struct tty_driver *driver, unsigned index, struct device *dev); struct device *tty_register_device_attr(struct tty_driver *driver, unsigned index, struct device *device, void *drvdata, const struct attribute_group **attr_grp); void tty_unregister_device(struct tty_driver *driver, unsigned index); #ifdef CONFIG_PROC_FS void proc_tty_register_driver(struct tty_driver *); void proc_tty_unregister_driver(struct tty_driver *); #else static inline void proc_tty_register_driver(struct tty_driver *d) {} static inline void proc_tty_unregister_driver(struct tty_driver *d) {} #endif #endif /* #ifdef _LINUX_TTY_DRIVER_H */
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