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/* 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 {
struct tty_struct * (*lookup)(struct tty_driver *driver,
struct file *filp, int idx);
int (*install)(struct tty_driver *driver, struct tty_struct *tty);
void (*remove)(struct tty_driver *driver, struct tty_struct *tty);
int (*open)(struct tty_struct * tty, struct file * filp);
void (*close)(struct tty_struct * tty, struct file * filp);
void (*shutdown)(struct tty_struct *tty);
void (*cleanup)(struct tty_struct *tty);
ssize_t (*write)(struct tty_struct *tty, const u8 *buf, size_t count);
int (*put_char)(struct tty_struct *tty, u8 ch);
void (*flush_chars)(struct tty_struct *tty);
unsigned int (*write_room)(struct tty_struct *tty);
unsigned int (*chars_in_buffer)(struct tty_struct *tty);
int (*ioctl)(struct tty_struct *tty,
unsigned int cmd, unsigned long arg);
long (*compat_ioctl)(struct tty_struct *tty,
unsigned int cmd, unsigned long arg);
void (*set_termios)(struct tty_struct *tty, const struct ktermios *old);
void (*throttle)(struct tty_struct * tty);
void (*unthrottle)(struct tty_struct * tty);
void (*stop)(struct tty_struct *tty);
void (*start)(struct tty_struct *tty);
void (*hangup)(struct tty_struct *tty);
int (*break_ctl)(struct tty_struct *tty, int state);
void (*flush_buffer)(struct tty_struct *tty);
int (*ldisc_ok)(struct tty_struct *tty, int ldisc);
void (*set_ldisc)(struct tty_struct *tty);
void (*wait_until_sent)(struct tty_struct *tty, int timeout);
void (*send_xchar)(struct tty_struct *tty, u8 ch);
int (*tiocmget)(struct tty_struct *tty);
int (*tiocmset)(struct tty_struct *tty,
unsigned int set, unsigned int clear);
int (*resize)(struct tty_struct *tty, struct winsize *ws);
int (*get_icount)(struct tty_struct *tty,
struct serial_icounter_struct *icount);
int (*get_serial)(struct tty_struct *tty, struct serial_struct *p);
int (*set_serial)(struct tty_struct *tty, struct serial_struct *p);
void (*show_fdinfo)(struct tty_struct *tty, struct seq_file *m);
#ifdef CONFIG_CONSOLE_POLL
int (*poll_init)(struct tty_driver *driver, int line, char *options);
int (*poll_get_char)(struct tty_driver *driver, int line);
void (*poll_put_char)(struct tty_driver *driver, int line, char ch);
#endif
int (*proc_show)(struct seq_file *m, void *driver);
} __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 {
struct kref kref;
struct cdev **cdevs;
struct module *owner;
const char *driver_name;
const char *name;
int name_base;
int major;
int minor_start;
unsigned int num;
short type;
short subtype;
struct ktermios init_termios;
unsigned long flags;
struct proc_dir_entry *proc_entry;
struct tty_driver *other;
/*
* Pointer to the tty data structures
*/
struct tty_struct **ttys;
struct tty_port **ports;
struct ktermios **termios;
void *driver_state;
/*
* Driver methods
*/
const struct tty_operations *ops;
struct list_head tty_drivers;
} __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) \
__tty_alloc_driver(lines, THIS_MODULE, flags)
static inline struct tty_driver *tty_driver_kref_get(struct tty_driver *d)
{
kref_get(&d->kref);
return d;
}
static inline void tty_set_operations(struct tty_driver *driver,
const struct tty_operations *op)
{
driver->ops = 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 0x0001
#define TTY_DRIVER_RESET_TERMIOS 0x0002
#define TTY_DRIVER_REAL_RAW 0x0004
#define TTY_DRIVER_DYNAMIC_DEV 0x0008
#define TTY_DRIVER_DEVPTS_MEM 0x0010
#define TTY_DRIVER_HARDWARE_BREAK 0x0020
#define TTY_DRIVER_DYNAMIC_ALLOC 0x0040
#define TTY_DRIVER_UNNUMBERED_NODE 0x0080
/* tty driver types */
#define TTY_DRIVER_TYPE_SYSTEM 0x0001
#define TTY_DRIVER_TYPE_CONSOLE 0x0002
#define TTY_DRIVER_TYPE_SERIAL 0x0003
#define TTY_DRIVER_TYPE_PTY 0x0004
#define TTY_DRIVER_TYPE_SCC 0x0005 /* scc driver */
#define TTY_DRIVER_TYPE_SYSCONS 0x0006
/* system subtypes (magic, used by tty_io.c) */
#define SYSTEM_TYPE_TTY 0x0001
#define SYSTEM_TYPE_CONSOLE 0x0002
#define SYSTEM_TYPE_SYSCONS 0x0003
#define SYSTEM_TYPE_SYSPTMX 0x0004
/* pty subtypes (magic, used by tty_io.c) */
#define PTY_TYPE_MASTER 0x0001
#define PTY_TYPE_SLAVE 0x0002
/* serial subtype definitions */
#define SERIAL_TYPE_NORMAL 1
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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