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Diffstat (limited to 'include/linux/tty_ldisc.h')
| -rw-r--r-- | include/linux/tty_ldisc.h | 270 |
1 files changed, 270 insertions, 0 deletions
diff --git a/include/linux/tty_ldisc.h b/include/linux/tty_ldisc.h new file mode 100644 index 000000000..dcb61ec11 --- /dev/null +++ b/include/linux/tty_ldisc.h @@ -0,0 +1,270 @@ +/* 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. + * + * 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. + * + * 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. + * + * @read: [TTY] ``ssize_t ()(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. Multiple read calls may occur in parallel and the ldisc + * must deal with serialization issues. + * + * Can sleep. + * + * @write: [TTY] ``ssize_t ()(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. + * + * 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. + * + * @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. + * + * @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. + * + * @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. + * + * @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. + * + * Can sleep. + * + * @receive_buf: [DRV] ``void ()(struct tty_struct *tty, + * const unsigned char *cp, const 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 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. + * + * @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. + * + * @dcd_change: [DRV] ``void ()(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. + * + * @receive_buf2: [DRV] ``int ()(struct tty_struct *tty, + * const unsigned char *cp, const 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 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. + * + * @lookahead_buf: [DRV] ``void ()(struct tty_struct *tty, + * const unsigned char *cp, const char *fp, int 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()). + * + * @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, + 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, 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 unsigned char *cp, + const char *fp, int count); + void (*write_wakeup)(struct tty_struct *tty); + void (*dcd_change)(struct tty_struct *tty, unsigned int status); + int (*receive_buf2)(struct tty_struct *tty, const unsigned char *cp, + const char *fp, int count); + void (*lookahead_buf)(struct tty_struct *tty, const unsigned char *cp, + const unsigned char *fp, unsigned 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 */ |