1 /*
2 * A simple kernel FIFO implementation.
3 *
4 * Copyright (C) 2004 Stelian Pop <stelian@popies.net>
5 *
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation; either version 2 of the License, or
9 * (at your option) any later version.
10 *
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
15 *
16 * You should have received a copy of the GNU General Public License
17 * along with this program; if not, write to the Free Software
18 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
19 *
20 */
21 #ifndef _LINUX_KFIFO_H
22 #define _LINUX_KFIFO_H
23
24 #ifdef __KERNEL__
25
26 #include <linux/kernel.h>
27 #include <linux/spinlock.h>
28
29 struct kfifo {
30 unsigned char *buffer; /* the buffer holding the data */
31 unsigned int size; /* the size of the allocated buffer */
32 unsigned int in; /* data is added at offset (in % size) */
33 unsigned int out; /* data is extracted from off. (out % size) */
34 spinlock_t *lock; /* protects concurrent modifications */
35 };
36
37 extern struct kfifo *kfifo_init(unsigned char *buffer, unsigned int size,
38 gfp_t gfp_mask, spinlock_t *lock);
39 extern struct kfifo *kfifo_alloc(unsigned int size, gfp_t gfp_mask,
40 spinlock_t *lock);
41 extern void kfifo_free(struct kfifo *fifo);
42 extern unsigned int __kfifo_put(struct kfifo *fifo,
43 unsigned char *buffer, unsigned int len);
44 extern unsigned int __kfifo_get(struct kfifo *fifo,
45 unsigned char *buffer, unsigned int len);
46
47 /**
48 * __kfifo_reset - removes the entire FIFO contents, no locking version
49 * @fifo: the fifo to be emptied.
50 */
51 static inline void __kfifo_reset(struct kfifo *fifo)
52 {
53 fifo->in = fifo->out = 0;
54 }
55
56 /**
57 * kfifo_reset - removes the entire FIFO contents
58 * @fifo: the fifo to be emptied.
59 */
60 static inline void kfifo_reset(struct kfifo *fifo)
61 {
62 unsigned long flags;
63
64 spin_lock_irqsave(fifo->lock, flags);
65
66 __kfifo_reset(fifo);
67
68 spin_unlock_irqrestore(fifo->lock, flags);
69 }
70
71 /**
72 * kfifo_put - puts some data into the FIFO
73 * @fifo: the fifo to be used.
74 * @buffer: the data to be added.
75 * @len: the length of the data to be added.
76 *
77 * This function copies at most @len bytes from the @buffer into
78 * the FIFO depending on the free space, and returns the number of
79 * bytes copied.
80 */
81 static inline unsigned int kfifo_put(struct kfifo *fifo,
82 unsigned char *buffer, unsigned int len)
83 {
84 unsigned long flags;
85 unsigned int ret;
86
87 spin_lock_irqsave(fifo->lock, flags);
88
89 ret = __kfifo_put(fifo, buffer, len);
90
91 spin_unlock_irqrestore(fifo->lock, flags);
92
93 return ret;
94 }
95
96 /**
97 * kfifo_get - gets some data from the FIFO
98 * @fifo: the fifo to be used.
99 * @buffer: where the data must be copied.
100 * @len: the size of the destination buffer.
101 *
102 * This function copies at most @len bytes from the FIFO into the
103 * @buffer and returns the number of copied bytes.
104 */
105 static inline unsigned int kfifo_get(struct kfifo *fifo,
106 unsigned char *buffer, unsigned int len)
107 {
108 unsigned long flags;
109 unsigned int ret;
110
111 spin_lock_irqsave(fifo->lock, flags);
112
113 ret = __kfifo_get(fifo, buffer, len);
114
115 /*
116 * optimization: if the FIFO is empty, set the indices to 0
117 * so we don't wrap the next time
118 */
119 if (fifo->in == fifo->out)
120 fifo->in = fifo->out = 0;
121
122 spin_unlock_irqrestore(fifo->lock, flags);
123
124 return ret;
125 }
126
127 /**
128 * __kfifo_len - returns the number of bytes available in the FIFO, no locking version
129 * @fifo: the fifo to be used.
130 */
131 static inline unsigned int __kfifo_len(struct kfifo *fifo)
132 {
133 return fifo->in - fifo->out;
134 }
135
136 /**
137 * kfifo_len - returns the number of bytes available in the FIFO
138 * @fifo: the fifo to be used.
139 */
140 static inline unsigned int kfifo_len(struct kfifo *fifo)
141 {
142 unsigned long flags;
143 unsigned int ret;
144
145 spin_lock_irqsave(fifo->lock, flags);
146
147 ret = __kfifo_len(fifo);
148
149 spin_unlock_irqrestore(fifo->lock, flags);
150
151 return ret;
152 }
153
154 #else
155 #warning "don't include kernel headers in userspace"
156 #endif /* __KERNEL__ */
157 #endif
158
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