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