/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_TTY_LDISC_H
#define _LINUX_TTY_LDISC_H
struct tty_struct;
#include <linux/fs.h>
#include <linux/wait.h>
#include <linux/atomic.h>
#include <linux/list.h>
#include <linux/lockdep.h>
#include <linux/seq_file.h>
/*
* the semaphore definition
*/
struct ld_semaphore {
atomic_long_t count;
raw_spinlock_t wait_lock;
unsigned int wait_readers;
struct list_head read_wait;
struct list_head write_wait;
#ifdef CONFIG_DEBUG_LOCK_ALLOC
struct lockdep_map dep_map;
#endif
};
void __init_ldsem(struct ld_semaphore *sem, const char *name,
struct lock_class_key *key);
#define init_ldsem(sem) \
do { \
static struct lock_class_key __key; \
\
__init_ldsem((sem), #sem, &__key); \
} while (0)
int ldsem_down_read(struct ld_semaphore *sem, long timeout);
int ldsem_down_read_trylock(struct ld_semaphore *sem);
int ldsem_down_write(struct ld_semaphore *sem, long timeout);
int ldsem_down_write_trylock(struct ld_semaphore *sem);
void ldsem_up_read(struct ld_semaphore *sem);
void ldsem_up_write(struct ld_semaphore *sem);
#ifdef CONFIG_DEBUG_LOCK_ALLOC
int ldsem_down_read_nested(struct ld_semaphore *sem, int subclass,
long timeout);
int ldsem_down_write_nested(struct ld_semaphore *sem, int subclass,
long timeout);
#else
# define ldsem_down_read_nested(sem, subclass, timeout) \
ldsem_down_read(sem, timeout)
# define ldsem_down_write_nested(sem, subclass, timeout) \
ldsem_down_write(sem, timeout)
#endif
/**
* struct tty_ldisc_ops - ldisc operations
*
* @name: name of this ldisc rendered in /proc/tty/ldiscs
* @num: ``N_*`` number (%N_TTY, %N_HDLC, ...) reserved to this ldisc
*
* @open: [TTY] ``int ()(struct tty_struct *tty)``
*
* This function is called when the line discipline is associated with the
* @tty. No other call into the line discipline for this tty will occur
* until it completes successfully. It should initialize any state needed
* by the ldisc, and set @tty->receive_room to the maximum amount of data
* the line discipline is willing to accept from the driver with a single
* call to @receive_buf(). Returning an error will prevent the ldisc from
* being attached.
*
* Optional. Can sleep.
*
* @close: [TTY] ``void ()(struct tty_struct *tty)``
*
* This function is called when the line discipline is being shutdown,
* either because the @tty is being closed or because the @tty is being
* changed to use a new line discipline. At the point of execution no
* further users will enter the ldisc code for this tty.
*
* Optional. Can sleep.
*
* @flush_buffer: [TTY] ``void ()(struct tty_struct *tty)``
*
* This function instructs the line discipline to clear its buffers of any
* input characters it may have queued to be delivered to the user mode
* process. It may be called at any point between open and close.
*
* Optional.
*
* @read: [TTY] ``ssize_t ()(struct tty_struct *tty, struct file *file, u8 *buf,
* size_t nr)``
*
* This function is called when the user requests to read from the @tty.
* The line discipline will return whatever characters it has buffered up
* for the user. If this function is not defined, the user will receive
* an %EIO error. Multiple read calls may occur in parallel and the ldisc
* must deal with serialization issues.
*
* Optional: %EIO unless provided. Can sleep.
*
* @write: [TTY] ``ssize_t ()(struct tty_struct *tty, struct file *file,
* const u8 *buf, size_t nr)``
*
* This function is called when the user requests to write to the @tty.
* The line discipline will deliver the characters to the low-level tty
* device for transmission, optionally performing some processing on the
* characters first. If this function is not defined, the user will
* receive an %EIO error.
*
* Optional: %EIO unless provided. Can sleep.
*
* @ioctl: [TTY] ``int ()(struct tty_struct *tty, unsigned int cmd,
* unsigned long arg)``
*
* This function is called when the user requests an ioctl which is not
* handled by the tty layer or the low-level tty driver. It is intended
* for ioctls which affect line discpline operation. Note that the search
* order for ioctls is (1) tty layer, (2) tty low-level driver, (3) line
* discpline. So a low-level driver can "grab" an ioctl request before
* the line discpline has a chance to see it.
*
* Optional.
*
* @compat_ioctl: [TTY] ``int ()(struct tty_struct *tty, unsigned int cmd,
* unsigned long arg)``
*
* Process ioctl calls from 32-bit process on 64-bit system.
*
* Note that only ioctls that are neither "pointer to compatible
* structure" nor tty-generic. Something private that takes an integer or
* a pointer to wordsize-sensitive structure belongs here, but most of
* ldiscs will happily leave it %NULL.
*
* Optional.
*
* @set_termios: [TTY] ``void ()(struct tty_struct *tty, const struct ktermios *old)``
*
* This function notifies the line discpline that a change has been made
* to the termios structure.
*
* Optional.
*
* @poll: [TTY] ``int ()(struct tty_struct *tty, struct file *file,
* struct poll_table_struct *wait)``
*
* This function is called when a user attempts to select/poll on a @tty
* device. It is solely the responsibility of the line discipline to
* handle poll requests.
*
* Optional.
*
* @hangup: [TTY] ``void ()(struct tty_struct *tty)``
*
* Called on a hangup. Tells the discipline that it should cease I/O to
* the tty driver. The driver should seek to perform this action quickly
* but should wait until any pending driver I/O is completed. No further
* calls into the ldisc code will occur.
*
* Optional. Can sleep.
*
* @receive_buf: [DRV] ``void ()(struct tty_struct *tty, const u8 *cp,
* const u8 *fp, size_t count)``
*
* This function is called by the low-level tty driver to send characters
* received by the hardware to the line discpline for processing. @cp is
* a pointer to the buffer of input character received by the device. @fp
* is a pointer to an array of flag bytes which indicate whether a
* character was received with a parity error, etc. @fp may be %NULL to
* indicate all data received is %TTY_NORMAL.
*
* Optional.
*
* @write_wakeup: [DRV] ``void ()(struct tty_struct *tty)``
*
* This function is called by the low-level tty driver to signal that line
* discpline should try to send more characters to the low-level driver
* for transmission. If the line discpline does not have any more data to
* send, it can just return. If the line discipline does have some data to
* send, please arise a tasklet or workqueue to do the real data transfer.
* Do not send data in this hook, it may lead to a deadlock.
*
* Optional.
*
* @dcd_change: [DRV] ``void ()(struct tty_struct *tty, bool active)``
*
* Tells the discipline that the DCD pin has changed its status. Used
* exclusively by the %N_PPS (Pulse-Per-Second) line discipline.
*
* Optional.
*
* @receive_buf2: [DRV] ``ssize_t ()(struct tty_struct *tty, const u8 *cp,
* const u8 *fp, size_t count)``
*
* This function is called by the low-level tty driver to send characters
* received by the hardware to the line discpline for processing. @cp is a
* pointer to the buffer of input character received by the device. @fp
* is a pointer to an array of flag bytes which indicate whether a
* character was received with a parity error, etc. @fp may be %NULL to
* indicate all data received is %TTY_NORMAL. If assigned, prefer this
* function for automatic flow control.
*
* Optional.
*
* @lookahead_buf: [DRV] ``void ()(struct tty_struct *tty, const u8 *cp,
* const u8 *fp, size_t count)``
*
* This function is called by the low-level tty driver for characters
* not eaten by ->receive_buf() or ->receive_buf2(). It is useful for
* processing high-priority characters such as software flow-control
* characters that could otherwise get stuck into the intermediate
* buffer until tty has room to receive them. Ldisc must be able to
* handle later a ->receive_buf() or ->receive_buf2() call for the
* same characters (e.g. by skipping the actions for high-priority
* characters already handled by ->lookahead_buf()).
*
* Optional.
*
* @owner: module containting this ldisc (for reference counting)
*
* This structure defines the interface between the tty line discipline
* implementation and the tty routines. The above routines can be defined.
* Unless noted otherwise, they are optional, and can be filled in with a %NULL
* pointer.
*
* Hooks marked [TTY] are invoked from the TTY core, the [DRV] ones from the
* tty_driver side.
*/
struct tty_ldisc_ops {
char *name;
int num;
/*
* The following routines are called from above.
*/
int (*open)(struct tty_struct *tty);
void (*close)(struct tty_struct *tty);
void (*flush_buffer)(struct tty_struct *tty);
ssize_t (*read)(struct tty_struct *tty, struct file *file, u8 *buf,
size_t nr, void **cookie, unsigned long offset);
ssize_t (*write)(struct tty_struct *tty, struct file *file,
const u8 *buf, size_t nr);
int (*ioctl)(struct tty_struct *tty, unsigned int cmd,
unsigned long arg);
int (*compat_ioctl)(struct tty_struct *tty, unsigned int cmd,
unsigned long arg);
void (*set_termios)(struct tty_struct *tty, const struct ktermios *old);
__poll_t (*poll)(struct tty_struct *tty, struct file *file,
struct poll_table_struct *wait);
void (*hangup)(struct tty_struct *tty);
/*
* The following routines are called from below.
*/
void (*receive_buf)(struct tty_struct *tty, const u8 *cp,
const u8 *fp, size_t count);
void (*write_wakeup)(struct tty_struct *tty);
void (*dcd_change)(struct tty_struct *tty, bool active);
size_t (*receive_buf2)(struct tty_struct *tty, const u8 *cp,
const u8 *fp, size_t count);
void (*lookahead_buf)(struct tty_struct *tty, const u8 *cp,
const u8 *fp, size_t count);
struct module *owner;
};
struct tty_ldisc {
struct tty_ldisc_ops *ops;
struct tty_struct *tty;
};
#define MODULE_ALIAS_LDISC(ldisc) \
MODULE_ALIAS("tty-ldisc-" __stringify(ldisc))
extern const struct seq_operations tty_ldiscs_seq_ops;
struct tty_ldisc *tty_ldisc_ref(struct tty_struct *);
void tty_ldisc_deref(struct tty_ldisc *);
struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *);
void tty_ldisc_flush(struct tty_struct *tty);
int tty_register_ldisc(struct tty_ldisc_ops *new_ldisc);
void tty_unregister_ldisc(struct tty_ldisc_ops *ldisc);
int tty_set_ldisc(struct tty_struct *tty, int disc);
#endif /* _LINUX_TTY_LDISC_H */
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