1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _LINUX_TTY_LDISC_H
3 #define _LINUX_TTY_LDISC_H
4 
5 /*
6  * This structure defines the interface between the tty line discipline
7  * implementation and the tty routines.  The following routines can be
8  * defined; unless noted otherwise, they are optional, and can be
9  * filled in with a null pointer.
10  *
11  * int	(*open)(struct tty_struct *);
12  *
13  *	This function is called when the line discipline is associated
14  *	with the tty.  The line discipline can use this as an
15  *	opportunity to initialize any state needed by the ldisc routines.
16  *
17  * void	(*close)(struct tty_struct *);
18  *
19  *	This function is called when the line discipline is being
20  *	shutdown, either because the tty is being closed or because
21  *	the tty is being changed to use a new line discipline
22  *
23  * void	(*flush_buffer)(struct tty_struct *tty);
24  *
25  *	This function instructs the line discipline to clear its
26  *	buffers of any input characters it may have queued to be
27  *	delivered to the user mode process.
28  *
29  * ssize_t (*read)(struct tty_struct * tty, struct file * file,
30  *		   unsigned char * buf, size_t nr);
31  *
32  *	This function is called when the user requests to read from
33  *	the tty.  The line discipline will return whatever characters
34  *	it has buffered up for the user.  If this function is not
35  *	defined, the user will receive an EIO error.
36  *
37  * ssize_t (*write)(struct tty_struct * tty, struct file * file,
38  *		    const unsigned char * buf, size_t nr);
39  *
40  *	This function is called when the user requests to write to the
41  *	tty.  The line discipline will deliver the characters to the
42  *	low-level tty device for transmission, optionally performing
43  *	some processing on the characters first.  If this function is
44  *	not defined, the user will receive an EIO error.
45  *
46  * int	(*ioctl)(struct tty_struct * tty, struct file * file,
47  *		 unsigned int cmd, unsigned long arg);
48  *
49  *	This function is called when the user requests an ioctl which
50  *	is not handled by the tty layer or the low-level tty driver.
51  *	It is intended for ioctls which affect line discpline
52  *	operation.  Note that the search order for ioctls is (1) tty
53  *	layer, (2) tty low-level driver, (3) line discpline.  So a
54  *	low-level driver can "grab" an ioctl request before the line
55  *	discpline has a chance to see it.
56  *
57  * long	(*compat_ioctl)(struct tty_struct * tty, struct file * file,
58  *		        unsigned int cmd, unsigned long arg);
59  *
60  *	Process ioctl calls from 32-bit process on 64-bit system
61  *
62  * void	(*set_termios)(struct tty_struct *tty, struct ktermios * old);
63  *
64  *	This function notifies the line discpline that a change has
65  *	been made to the termios structure.
66  *
67  * int	(*poll)(struct tty_struct * tty, struct file * file,
68  *		  poll_table *wait);
69  *
70  *	This function is called when a user attempts to select/poll on a
71  *	tty device.  It is solely the responsibility of the line
72  *	discipline to handle poll requests.
73  *
74  * void	(*receive_buf)(struct tty_struct *, const unsigned char *cp,
75  *		       char *fp, int count);
76  *
77  *	This function is called by the low-level tty driver to send
78  *	characters received by the hardware to the line discpline for
79  *	processing.  <cp> is a pointer to the buffer of input
80  *	character received by the device.  <fp> is a pointer to a
81  *	pointer of flag bytes which indicate whether a character was
82  *	received with a parity error, etc. <fp> may be NULL to indicate
83  *	all data received is TTY_NORMAL.
84  *
85  * void	(*write_wakeup)(struct tty_struct *);
86  *
87  *	This function is called by the low-level tty driver to signal
88  *	that line discpline should try to send more characters to the
89  *	low-level driver for transmission.  If the line discpline does
90  *	not have any more data to send, it can just return. If the line
91  *	discipline does have some data to send, please arise a tasklet
92  *	or workqueue to do the real data transfer. Do not send data in
93  *	this hook, it may leads to a deadlock.
94  *
95  * int (*hangup)(struct tty_struct *)
96  *
97  *	Called on a hangup. Tells the discipline that it should
98  *	cease I/O to the tty driver. Can sleep. The driver should
99  *	seek to perform this action quickly but should wait until
100  *	any pending driver I/O is completed.
101  *
102  * void (*dcd_change)(struct tty_struct *tty, unsigned int status)
103  *
104  *	Tells the discipline that the DCD pin has changed its status.
105  *	Used exclusively by the N_PPS (Pulse-Per-Second) line discipline.
106  *
107  * int	(*receive_buf2)(struct tty_struct *, const unsigned char *cp,
108  *			char *fp, int count);
109  *
110  *	This function is called by the low-level tty driver to send
111  *	characters received by the hardware to the line discpline for
112  *	processing.  <cp> is a pointer to the buffer of input
113  *	character received by the device.  <fp> is a pointer to a
114  *	pointer of flag bytes which indicate whether a character was
115  *	received with a parity error, etc. <fp> may be NULL to indicate
116  *	all data received is TTY_NORMAL.
117  *	If assigned, prefer this function for automatic flow control.
118  */
119 
120 #include <linux/fs.h>
121 #include <linux/wait.h>
122 #include <linux/atomic.h>
123 
124 /*
125  * the semaphore definition
126  */
127 struct ld_semaphore {
128 	atomic_long_t		count;
129 	raw_spinlock_t		wait_lock;
130 	unsigned int		wait_readers;
131 	struct list_head	read_wait;
132 	struct list_head	write_wait;
133 #ifdef CONFIG_DEBUG_LOCK_ALLOC
134 	struct lockdep_map	dep_map;
135 #endif
136 };
137 
138 extern void __init_ldsem(struct ld_semaphore *sem, const char *name,
139 			 struct lock_class_key *key);
140 
141 #define init_ldsem(sem)						\
142 do {								\
143 	static struct lock_class_key __key;			\
144 								\
145 	__init_ldsem((sem), #sem, &__key);			\
146 } while (0)
147 
148 
149 extern int ldsem_down_read(struct ld_semaphore *sem, long timeout);
150 extern int ldsem_down_read_trylock(struct ld_semaphore *sem);
151 extern int ldsem_down_write(struct ld_semaphore *sem, long timeout);
152 extern int ldsem_down_write_trylock(struct ld_semaphore *sem);
153 extern void ldsem_up_read(struct ld_semaphore *sem);
154 extern void ldsem_up_write(struct ld_semaphore *sem);
155 
156 #ifdef CONFIG_DEBUG_LOCK_ALLOC
157 extern int ldsem_down_read_nested(struct ld_semaphore *sem, int subclass,
158 				  long timeout);
159 extern int ldsem_down_write_nested(struct ld_semaphore *sem, int subclass,
160 				   long timeout);
161 #else
162 # define ldsem_down_read_nested(sem, subclass, timeout)		\
163 		ldsem_down_read(sem, timeout)
164 # define ldsem_down_write_nested(sem, subclass, timeout)	\
165 		ldsem_down_write(sem, timeout)
166 #endif
167 
168 
169 struct tty_ldisc_ops {
170 	int	magic;
171 	char	*name;
172 	int	num;
173 	int	flags;
174 
175 	/*
176 	 * The following routines are called from above.
177 	 */
178 	int	(*open)(struct tty_struct *);
179 	void	(*close)(struct tty_struct *);
180 	void	(*flush_buffer)(struct tty_struct *tty);
181 	ssize_t	(*read)(struct tty_struct *tty, struct file *file,
182 			unsigned char __user *buf, size_t nr);
183 	ssize_t	(*write)(struct tty_struct *tty, struct file *file,
184 			 const unsigned char *buf, size_t nr);
185 	int	(*ioctl)(struct tty_struct *tty, struct file *file,
186 			 unsigned int cmd, unsigned long arg);
187 	long	(*compat_ioctl)(struct tty_struct *tty, struct file *file,
188 				unsigned int cmd, unsigned long arg);
189 	void	(*set_termios)(struct tty_struct *tty, struct ktermios *old);
190 	__poll_t (*poll)(struct tty_struct *, struct file *,
191 			     struct poll_table_struct *);
192 	int	(*hangup)(struct tty_struct *tty);
193 
194 	/*
195 	 * The following routines are called from below.
196 	 */
197 	void	(*receive_buf)(struct tty_struct *, const unsigned char *cp,
198 			       char *fp, int count);
199 	void	(*write_wakeup)(struct tty_struct *);
200 	void	(*dcd_change)(struct tty_struct *, unsigned int);
201 	int	(*receive_buf2)(struct tty_struct *, const unsigned char *cp,
202 				char *fp, int count);
203 
204 	struct  module *owner;
205 
206 	int refcount;
207 };
208 
209 struct tty_ldisc {
210 	struct tty_ldisc_ops *ops;
211 	struct tty_struct *tty;
212 };
213 
214 #define TTY_LDISC_MAGIC	0x5403
215 
216 #define LDISC_FLAG_DEFINED	0x00000001
217 
218 #define MODULE_ALIAS_LDISC(ldisc) \
219 	MODULE_ALIAS("tty-ldisc-" __stringify(ldisc))
220 
221 #endif /* _LINUX_TTY_LDISC_H */
222