xref: /linux/include/linux/tty_buffer.h (revision a1c613ae4c322ddd58d5a8539dbfba2a0380a8c0)
1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _LINUX_TTY_BUFFER_H
3 #define _LINUX_TTY_BUFFER_H
4 
5 #include <linux/atomic.h>
6 #include <linux/llist.h>
7 #include <linux/mutex.h>
8 #include <linux/workqueue.h>
9 
10 struct tty_buffer {
11 	union {
12 		struct tty_buffer *next;
13 		struct llist_node free;
14 	};
15 	unsigned int used;
16 	unsigned int size;
17 	unsigned int commit;
18 	unsigned int lookahead;		/* Lazy update on recv, can become less than "read" */
19 	unsigned int read;
20 	bool flags;
21 	/* Data points here */
22 	u8 data[] __aligned(sizeof(unsigned long));
23 };
24 
char_buf_ptr(struct tty_buffer * b,unsigned int ofs)25 static inline u8 *char_buf_ptr(struct tty_buffer *b, unsigned int ofs)
26 {
27 	return b->data + ofs;
28 }
29 
flag_buf_ptr(struct tty_buffer * b,unsigned int ofs)30 static inline u8 *flag_buf_ptr(struct tty_buffer *b, unsigned int ofs)
31 {
32 	return char_buf_ptr(b, ofs) + b->size;
33 }
34 
35 struct tty_bufhead {
36 	struct tty_buffer *head;	/* Queue head */
37 	struct work_struct work;
38 	struct mutex	   lock;
39 	atomic_t	   priority;
40 	struct tty_buffer sentinel;
41 	struct llist_head free;		/* Free queue head */
42 	atomic_t	   mem_used;    /* In-use buffers excluding free list */
43 	int		   mem_limit;
44 	struct tty_buffer *tail;	/* Active buffer */
45 };
46 
47 /*
48  * When a break, frame error, or parity error happens, these codes are
49  * stuffed into the flags buffer.
50  */
51 #define TTY_NORMAL	0
52 #define TTY_BREAK	1
53 #define TTY_FRAME	2
54 #define TTY_PARITY	3
55 #define TTY_OVERRUN	4
56 
57 #endif
58