1 #ifndef _LINUX_TTY_LDISC_H
2 #define _LINUX_TTY_LDISC_H
3 
4 /*
5  * This structure defines the interface between the tty line discipline
6  * implementation and the tty routines.  The following routines can be
7  * defined; unless noted otherwise, they are optional, and can be
8  * filled in with a null pointer.
9  *
10  * int	(*open)(struct tty_struct *);
11  *
12  * 	This function is called when the line discipline is associated
13  * 	with the tty.  The line discipline can use this as an
14  * 	opportunity to initialize any state needed by the ldisc routines.
15  *
16  * void	(*close)(struct tty_struct *);
17  *
18  *	This function is called when the line discipline is being
19  * 	shutdown, either because the tty is being closed or because
20  * 	the tty is being changed to use a new line discipline
21  *
22  * void	(*flush_buffer)(struct tty_struct *tty);
23  *
24  * 	This function instructs the line discipline to clear its
25  * 	buffers of any input characters it may have queued to be
26  * 	delivered to the user mode process.
27  *
28  * ssize_t (*chars_in_buffer)(struct tty_struct *tty);
29  *
30  * 	This function returns the number of input characters the line
31  *	discipline may have queued up to be delivered to the user mode
32  *	process.
33  *
34  * ssize_t (*read)(struct tty_struct * tty, struct file * file,
35  *		   unsigned char * buf, size_t nr);
36  *
37  * 	This function is called when the user requests to read from
38  * 	the tty.  The line discipline will return whatever characters
39  * 	it has buffered up for the user.  If this function is not
40  * 	defined, the user will receive an EIO error.
41  *
42  * ssize_t (*write)(struct tty_struct * tty, struct file * file,
43  * 		    const unsigned char * buf, size_t nr);
44  *
45  * 	This function is called when the user requests to write to the
46  * 	tty.  The line discipline will deliver the characters to the
47  * 	low-level tty device for transmission, optionally performing
48  * 	some processing on the characters first.  If this function is
49  * 	not defined, the user will receive an EIO error.
50  *
51  * int	(*ioctl)(struct tty_struct * tty, struct file * file,
52  * 		 unsigned int cmd, unsigned long arg);
53  *
54  *	This function is called when the user requests an ioctl which
55  * 	is not handled by the tty layer or the low-level tty driver.
56  * 	It is intended for ioctls which affect line discpline
57  * 	operation.  Note that the search order for ioctls is (1) tty
58  * 	layer, (2) tty low-level driver, (3) line discpline.  So a
59  * 	low-level driver can "grab" an ioctl request before the line
60  * 	discpline has a chance to see it.
61  *
62  * void	(*set_termios)(struct tty_struct *tty, struct termios * 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.
83  *
84  * int	(*receive_room)(struct tty_struct *);
85  *
86  * 	This function is called by the low-level tty driver to
87  * 	determine how many characters the line discpline can accept.
88  * 	The low-level driver must not send more characters than was
89  * 	indicated by receive_room, or the line discpline may drop
90  * 	those characters.
91  *
92  * void	(*write_wakeup)(struct tty_struct *);
93  *
94  * 	This function is called by the low-level tty driver to signal
95  * 	that line discpline should try to send more characters to the
96  * 	low-level driver for transmission.  If the line discpline does
97  * 	not have any more data to send, it can just return.
98  *
99  * int (*hangup)(struct tty_struct *)
100  *
101  *	Called on a hangup. Tells the discipline that it should
102  *	cease I/O to the tty driver. Can sleep. The driver should
103  *	seek to perform this action quickly but should wait until
104  *	any pending driver I/O is completed.
105  */
106 
107 #include <linux/fs.h>
108 #include <linux/wait.h>
109 
110 struct tty_ldisc {
111 	int	magic;
112 	char	*name;
113 	int	num;
114 	int	flags;
115 	/*
116 	 * The following routines are called from above.
117 	 */
118 	int	(*open)(struct tty_struct *);
119 	void	(*close)(struct tty_struct *);
120 	void	(*flush_buffer)(struct tty_struct *tty);
121 	ssize_t	(*chars_in_buffer)(struct tty_struct *tty);
122 	ssize_t	(*read)(struct tty_struct * tty, struct file * file,
123 			unsigned char * buf, size_t nr);
124 	ssize_t	(*write)(struct tty_struct * tty, struct file * file,
125 			 const unsigned char * buf, size_t nr);
126 	int	(*ioctl)(struct tty_struct * tty, struct file * file,
127 			 unsigned int cmd, unsigned long arg);
128 	void	(*set_termios)(struct tty_struct *tty, struct termios * old);
129 	unsigned int (*poll)(struct tty_struct *, struct file *,
130 			     struct poll_table_struct *);
131 	int     (*hangup)(struct tty_struct *tty);
132 
133 	/*
134 	 * The following routines are called from below.
135 	 */
136 	void	(*receive_buf)(struct tty_struct *, const unsigned char *cp,
137 			       char *fp, int count);
138 	int	(*receive_room)(struct tty_struct *);
139 	void	(*write_wakeup)(struct tty_struct *);
140 	int	refcount;
141 };
142 
143 #define TTY_LDISC_MAGIC	0x5403
144 
145 #define LDISC_FLAG_DEFINED	0x00000001
146 
147 #endif /* _LINUX_TTY_LDISC_H */
148