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/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_TTY_LDISC_H
#define _LINUX_TTY_LDISC_H
/*
* This structure defines the interface between the tty line discipline
* implementation 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.
*
* int (*open)(struct tty_struct *);
*
* This function is called when the line discipline is associated
* with the tty. The line discipline can use this as an
* opportunity to initialize any state needed by the ldisc routines.
*
* void (*close)(struct tty_struct *);
*
* 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
*
* void (*flush_buffer)(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.
*
* ssize_t (*read)(struct tty_struct * tty, struct file * file,
* unsigned char * 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.
*
* ssize_t (*write)(struct tty_struct * tty, struct file * file,
* const unsigned char * 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.
*
* int (*ioctl)(struct tty_struct * tty, struct file * file,
* 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.
*
* int (*compat_ioctl)(struct tty_struct * tty, struct file * file,
* unsigned int cmd, unsigned long arg);
*
* Process ioctl calls from 32-bit process on 64-bit system
*
* NOTE: 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.
*
* void (*set_termios)(struct tty_struct *tty, struct ktermios * old);
*
* This function notifies the line discpline that a change has
* been made to the termios structure.
*
* int (*poll)(struct tty_struct * tty, struct file * file,
* poll_table *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.
*
* void (*receive_buf)(struct tty_struct *, const unsigned char *cp,
* char *fp, int 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 a
* pointer 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.
*
* void (*write_wakeup)(struct tty_struct *);
*
* 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 leads to a deadlock.
*
* int (*hangup)(struct tty_struct *)
*
* Called on a hangup. Tells the discipline that it should
* cease I/O to the tty driver. Can sleep. The driver should
* seek to perform this action quickly but should wait until
* any pending driver I/O is completed.
*
* void (*dcd_change)(struct tty_struct *tty, unsigned int status)
*
* Tells the discipline that the DCD pin has changed its status.
* Used exclusively by the N_PPS (Pulse-Per-Second) line discipline.
*
* int (*receive_buf2)(struct tty_struct *, const unsigned char *cp,
* char *fp, int 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 a
* pointer 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.
*/
#include <linux/fs.h>
#include <linux/wait.h>
#include <linux/atomic.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
};
extern 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)
extern int ldsem_down_read(struct ld_semaphore *sem, long timeout);
extern int ldsem_down_read_trylock(struct ld_semaphore *sem);
extern int ldsem_down_write(struct ld_semaphore *sem, long timeout);
extern int ldsem_down_write_trylock(struct ld_semaphore *sem);
extern void ldsem_up_read(struct ld_semaphore *sem);
extern void ldsem_up_write(struct ld_semaphore *sem);
#ifdef CONFIG_DEBUG_LOCK_ALLOC
extern int ldsem_down_read_nested(struct ld_semaphore *sem, int subclass,
long timeout);
extern 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 {
char *name;
int num;
int flags;
/*
* The following routines are called from above.
*/
int (*open)(struct tty_struct *);
void (*close)(struct tty_struct *);
void (*flush_buffer)(struct tty_struct *tty);
ssize_t (*read)(struct tty_struct *tty, struct file *file,
unsigned char *buf, size_t nr,
void **cookie, unsigned long offset);
ssize_t (*write)(struct tty_struct *tty, struct file *file,
const unsigned char *buf, size_t nr);
int (*ioctl)(struct tty_struct *tty, struct file *file,
unsigned int cmd, unsigned long arg);
int (*compat_ioctl)(struct tty_struct *tty, struct file *file,
unsigned int cmd, unsigned long arg);
void (*set_termios)(struct tty_struct *tty, struct ktermios *old);
__poll_t (*poll)(struct tty_struct *, struct file *,
struct poll_table_struct *);
int (*hangup)(struct tty_struct *tty);
/*
* The following routines are called from below.
*/
void (*receive_buf)(struct tty_struct *, const unsigned char *cp,
const char *fp, int count);
void (*write_wakeup)(struct tty_struct *);
void (*dcd_change)(struct tty_struct *, unsigned int);
int (*receive_buf2)(struct tty_struct *, const unsigned char *cp,
const char *fp, int count);
struct module *owner;
};
struct tty_ldisc {
struct tty_ldisc_ops *ops;
struct tty_struct *tty;
};
#define LDISC_FLAG_DEFINED 0x00000001
#define MODULE_ALIAS_LDISC(ldisc) \
MODULE_ALIAS("tty-ldisc-" __stringify(ldisc))
#endif /* _LINUX_TTY_LDISC_H */
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