fiq_debugger_ringbuf.h revision 2a2f434d743209cda09c68acd63cbcae8e6d17c6 
1/*
2 * drivers/staging/android/fiq_debugger/fiq_debugger_ringbuf.h
3 *
4 * simple lockless ringbuffer
5 *
6 * Copyright (C) 2010 Google, Inc.
7 *
8 * This software is licensed under the terms of the GNU General Public
9 * License version 2, as published by the Free Software Foundation, and
10 * may be copied, distributed, and modified under those terms.
11 *
12 * This program is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15 * GNU General Public License for more details.
16 */
17
18#include <linux/kernel.h>
19#include <linux/slab.h>
20
21struct fiq_debugger_ringbuf {
22	int len;
23	int head;
24	int tail;
25	u8 buf[];
26};
27
28
29static inline struct fiq_debugger_ringbuf *fiq_debugger_ringbuf_alloc(int len)
30{
31	struct fiq_debugger_ringbuf *rbuf;
32
33	rbuf = kzalloc(sizeof(*rbuf) + len, GFP_KERNEL);
34	if (rbuf == NULL)
35		return NULL;
36
37	rbuf->len = len;
38	rbuf->head = 0;
39	rbuf->tail = 0;
40	smp_mb();
41
42	return rbuf;
43}
44
45static inline void fiq_debugger_ringbuf_free(struct fiq_debugger_ringbuf *rbuf)
46{
47	kfree(rbuf);
48}
49
50static inline int fiq_debugger_ringbuf_level(struct fiq_debugger_ringbuf *rbuf)
51{
52	int level = rbuf->head - rbuf->tail;
53
54	if (level < 0)
55		level = rbuf->len + level;
56
57	return level;
58}
59
60static inline int fiq_debugger_ringbuf_room(struct fiq_debugger_ringbuf *rbuf)
61{
62	return rbuf->len - fiq_debugger_ringbuf_level(rbuf) - 1;
63}
64
65static inline u8
66fiq_debugger_ringbuf_peek(struct fiq_debugger_ringbuf *rbuf, int i)
67{
68	return rbuf->buf[(rbuf->tail + i) % rbuf->len];
69}
70
71static inline int
72fiq_debugger_ringbuf_consume(struct fiq_debugger_ringbuf *rbuf, int count)
73{
74	count = min(count, fiq_debugger_ringbuf_level(rbuf));
75
76	rbuf->tail = (rbuf->tail + count) % rbuf->len;
77	smp_mb();
78
79	return count;
80}
81
82static inline int
83fiq_debugger_ringbuf_push(struct fiq_debugger_ringbuf *rbuf, u8 datum)
84{
85	if (fiq_debugger_ringbuf_room(rbuf) == 0)
86		return 0;
87
88	rbuf->buf[rbuf->head] = datum;
89	smp_mb();
90	rbuf->head = (rbuf->head + 1) % rbuf->len;
91	smp_mb();
92
93	return 1;
94}
95