/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_TTY_DRIVER_H
#define _LINUX_TTY_DRIVER_H

/*
 * This structure defines the interface between the low-level tty
 * driver and the tty routines.  The following routines can be
 * defined; unless noted otherwise, they are optional, and can be
 * filled in with a null pointer.
 *
 * struct tty_struct * (*lookup)(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 ttys array
 *
 * int (*install)(struct tty_driver *self, struct tty_struct *tty)
 *
 *      Install a new tty into the tty driver internal tables. Used in
 *      conjunction with lookup and remove methods.
 *
 *      Optional method. Default behaviour is to use the ttys array
 *
 * void (*remove)(struct tty_driver *self, struct tty_struct *tty)
 *
 *      Remove a closed tty from the tty driver internal tables. Used in
 *      conjunction with lookup and remove methods.
 *
 *      Optional method. Default behaviour is to use the ttys array
 *
 * int  (*open)(struct tty_struct * tty, struct file * filp);
 *
 *      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.
 *
 * void (*close)(struct tty_struct * tty, struct file * filp);
 *
 *      This routine is called when a particular tty device is closed.
 *      Note: called even if the corresponding open() failed.
 *
 *      Required method. Called with tty lock held.
 *
 * void (*shutdown)(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.
 *
 * void (*cleanup)(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.
 *
 *
 * int (*write)(struct tty_struct * tty,
 *               const unsigned char *buf, int count);
 *
 *      This routine is called by the kernel to write a series of
 *      characters 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.
 *
 *      Optional: Required for writable devices.
 *
 * int (*put_char)(struct tty_struct *tty, unsigned char ch);
 *
 *      This routine is called by the kernel to write a single
 *      character 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.
 *
 *      Note: Do not call this function directly, call tty_put_char
 *
 * void (*flush_chars)(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:
 *
 *      Note: Do not call this function directly, call tty_driver_flush_chars
 * 
 * unsigned int  (*write_room)(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.
 *
 *      Required if write method is provided else not needed.
 *
 *      Note: Do not call this function directly, call tty_write_room
 * 
 * int  (*ioctl)(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
 *
 * long (*compat_ioctl)(struct tty_struct *tty,,
 *                      unsigned int cmd, unsigned long arg);
 *
 *      implement ioctl processing for 32 bit process on 64 bit system
 *
 *      Optional
 * 
 * void (*set_termios)(struct tty_struct *tty, struct ktermios * old);
 *
 *      This routine allows the tty driver to be notified when
 *      device's termios settings have changed.
 *
 *      Optional: Called under the termios lock
 *
 *
 * void (*set_ldisc)(struct tty_struct *tty);
 *
 *      This routine allows the tty driver to be notified when the
 *      device's termios settings have changed.
 *
 *      Optional: Called under BKL (currently)
 * 
 * void (*throttle)(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.
 *
 *      Optional: Always invoke via tty_throttle_safe(), called under the
 *      termios lock.
 * 
 * void (*unthrottle)(struct tty_struct * tty);
 *
 *      This routine notifies the tty drivers that it should signals
 *      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
 *      termios lock.
 *
 * void (*stop)(struct tty_struct *tty);
 *
 *      This routine notifies the tty driver that it should stop
 *      outputting characters to the tty device.  
 *
 *      Called with ->flow.lock held. Serialized with start() method.
 *
 *      Optional:
 *
 *      Note: Call stop_tty not this method.
 * 
 * void (*start)(struct tty_struct *tty);
 *
 *      This routine notifies the tty driver that it resume sending
 *      characters to the tty device.
 *
 *      Called with ->flow.lock held. Serialized with stop() method.
 *
 *      Optional:
 *
 *      Note: Call start_tty not this method.
 * 
 * void (*hangup)(struct tty_struct *tty);
 *
 *      This routine notifies the tty driver that it should hang up the
 *      tty device.
 *
 *      Optional:
 *
 *      Called with tty lock held.
 *
 * int (*break_ctl)(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 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.
 *
 * void (*wait_until_sent)(struct tty_struct *tty, int timeout);
 * 
 *      This routine waits until the device has written out all of the
 *      characters in its transmitter FIFO.
 *
 *      Optional: If not provided the device is assumed to have no FIFO
 *
 *      Note: Usually correct to call tty_wait_until_sent
 *
 * void (*send_xchar)(struct tty_struct *tty, char ch);
 *
 *      This routine is used to send a high-priority XON/XOFF
 *      character to the device.
 *
 *      Optional: If not provided then the write method is called under
 *      the atomic write lock to keep it serialized with the ldisc.
 *
 * int (*resize)(struct tty_struct *tty, struct winsize *ws)
 *
 *      Called when a termios request is issued which changes the
 *      requested terminal geometry.
 *
 *      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 (eg a serial
 *      line). See tty_do_resize() if you need to wrap the standard method
 *      in your own logic - the usual case.
 *
 * int (*get_icount)(struct tty_struct *tty, struct serial_icounter *icount);
 *
 *      Called when the device receives a TIOCGICOUNT ioctl. Passed a kernel
 *      structure to complete. This method is optional and will only be called
 *      if provided (otherwise ENOTTY will be returned).
 */

#include <linux/export.h>
#include <linux/fs.h>
#include <linux/kref.h>
#include <linux/list.h>
#include <linux/cdev.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 {
        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);
        int  (*write)(struct tty_struct * tty,
                      const unsigned char *buf, int count);
        int  (*put_char)(struct tty_struct *tty, unsigned char 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, 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);
        void (*set_ldisc)(struct tty_struct *tty);
        void (*wait_until_sent)(struct tty_struct *tty, int timeout);
        void (*send_xchar)(struct tty_struct *tty, char 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 *, void *);
} __randomize_layout;

struct tty_driver {
        int     magic;          /* magic number for this structure */
        struct kref kref;       /* Reference management */
        struct cdev **cdevs;
        struct module   *owner;
        const char      *driver_name;
        const char      *name;
        int     name_base;      /* offset of printed name */
        int     major;          /* major device number */
        int     minor_start;    /* start of minor device number */
        unsigned int    num;    /* number of devices allocated */
        short   type;           /* type of tty driver */
        short   subtype;        /* subtype of tty driver */
        struct ktermios init_termios; /* Initial termios */
        unsigned long   flags;          /* tty driver flags */
        struct proc_dir_entry *proc_entry; /* /proc fs entry */
        struct tty_driver *other; /* only used for the PTY driver */

        /*
         * 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;

extern struct tty_driver *__tty_alloc_driver(unsigned int lines,
                struct module *owner, unsigned long flags);
extern struct tty_driver *tty_find_polling_driver(char *name, int *line);

extern 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;
}

/* tty driver magic number */
#define TTY_DRIVER_MAGIC                0x5402

/*
 * 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 PTY's, in particular.
 * 
 * TTY_DRIVER_REAL_RAW --- if set, indicates that the driver will
 *      guarantee never not to set any special character handling
 *      flags if ((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 --- if set, 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, 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, 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 caller instead of using a simple
 *      on/off interface.
 *
 * TTY_DRIVER_DYNAMIC_ALLOC -- do not allocate structures which are
 *      needed per line for this driver as it would waste memory.
 *      The driver will take care.
 *
 * TTY_DRIVER_UNNUMBERED_NODE -- do not create numbered /dev nodes. In
 *      other words 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 */