/* 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 { … }; void __init_ldsem(struct ld_semaphore *sem, const char *name, struct lock_class_key *key); #define init_ldsem(sem) … 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 … #define ldsem_down_write_nested … #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 { … }; struct tty_ldisc { … }; #define MODULE_ALIAS_LDISC(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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