/* SPDX-License-Identifier: GPL-2.0 */ #ifndef _LINUX_TTY_LDISC_H #define _LINUX_TTY_LDISC_H struct tty_struct; /* * 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. is a pointer to the buffer of input * character received by the device. is a pointer to a * pointer of flag bytes which indicate whether a character was * received with a parity error, etc. 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. is a pointer to the buffer of input * character received by the device. is a pointer to a * pointer of flag bytes which indicate whether a character was * received with a parity error, etc. may be NULL to indicate * all data received is TTY_NORMAL. * If assigned, prefer this function for automatic flow control. */ #include #include #include #include #include #include /* * 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 { char *name; int num; /* * 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 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 */