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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
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
22#include <linux/kernel.h>
23#include <linux/module.h>
24#include <linux/slab.h>
25#include <linux/err.h>
26#include <linux/kfifo.h>
vignesh babuf84d5a72007-07-15 23:41:34 -070027#include <linux/log2.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070028
29/**
30 * kfifo_init - allocates a new FIFO using a preallocated buffer
31 * @buffer: the preallocated buffer to be used.
32 * @size: the size of the internal buffer, this have to be a power of 2.
33 * @gfp_mask: get_free_pages mask, passed to kmalloc()
34 * @lock: the lock to be used to protect the fifo buffer
35 *
Robert P. J. Day72fd4a32007-02-10 01:45:59 -080036 * Do NOT pass the kfifo to kfifo_free() after use! Simply free the
37 * &struct kfifo with kfree().
Linus Torvalds1da177e2005-04-16 15:20:36 -070038 */
39struct kfifo *kfifo_init(unsigned char *buffer, unsigned int size,
Al Virodd0fc662005-10-07 07:46:04 +010040 gfp_t gfp_mask, spinlock_t *lock)
Linus Torvalds1da177e2005-04-16 15:20:36 -070041{
42 struct kfifo *fifo;
43
44 /* size must be a power of 2 */
vignesh babuf84d5a72007-07-15 23:41:34 -070045 BUG_ON(!is_power_of_2(size));
Linus Torvalds1da177e2005-04-16 15:20:36 -070046
47 fifo = kmalloc(sizeof(struct kfifo), gfp_mask);
48 if (!fifo)
49 return ERR_PTR(-ENOMEM);
50
51 fifo->buffer = buffer;
52 fifo->size = size;
53 fifo->in = fifo->out = 0;
54 fifo->lock = lock;
55
56 return fifo;
57}
58EXPORT_SYMBOL(kfifo_init);
59
60/**
61 * kfifo_alloc - allocates a new FIFO and its internal buffer
62 * @size: the size of the internal buffer to be allocated.
63 * @gfp_mask: get_free_pages mask, passed to kmalloc()
64 * @lock: the lock to be used to protect the fifo buffer
65 *
66 * The size will be rounded-up to a power of 2.
67 */
Al Virodd0fc662005-10-07 07:46:04 +010068struct kfifo *kfifo_alloc(unsigned int size, gfp_t gfp_mask, spinlock_t *lock)
Linus Torvalds1da177e2005-04-16 15:20:36 -070069{
70 unsigned char *buffer;
71 struct kfifo *ret;
72
73 /*
74 * round up to the next power of 2, since our 'let the indices
75 * wrap' tachnique works only in this case.
76 */
77 if (size & (size - 1)) {
78 BUG_ON(size > 0x80000000);
79 size = roundup_pow_of_two(size);
80 }
81
82 buffer = kmalloc(size, gfp_mask);
83 if (!buffer)
84 return ERR_PTR(-ENOMEM);
85
86 ret = kfifo_init(buffer, size, gfp_mask, lock);
87
88 if (IS_ERR(ret))
89 kfree(buffer);
90
91 return ret;
92}
93EXPORT_SYMBOL(kfifo_alloc);
94
95/**
96 * kfifo_free - frees the FIFO
97 * @fifo: the fifo to be freed.
98 */
99void kfifo_free(struct kfifo *fifo)
100{
101 kfree(fifo->buffer);
102 kfree(fifo);
103}
104EXPORT_SYMBOL(kfifo_free);
105
106/**
107 * __kfifo_put - puts some data into the FIFO, no locking version
108 * @fifo: the fifo to be used.
109 * @buffer: the data to be added.
110 * @len: the length of the data to be added.
111 *
Robert P. J. Day72fd4a32007-02-10 01:45:59 -0800112 * This function copies at most @len bytes from the @buffer into
Linus Torvalds1da177e2005-04-16 15:20:36 -0700113 * the FIFO depending on the free space, and returns the number of
114 * bytes copied.
115 *
116 * Note that with only one concurrent reader and one concurrent
117 * writer, you don't need extra locking to use these functions.
118 */
119unsigned int __kfifo_put(struct kfifo *fifo,
120 unsigned char *buffer, unsigned int len)
121{
122 unsigned int l;
123
124 len = min(len, fifo->size - fifo->in + fifo->out);
125
Paul E. McKenneya45bce42006-09-29 02:00:11 -0700126 /*
127 * Ensure that we sample the fifo->out index -before- we
128 * start putting bytes into the kfifo.
129 */
130
131 smp_mb();
132
Linus Torvalds1da177e2005-04-16 15:20:36 -0700133 /* first put the data starting from fifo->in to buffer end */
134 l = min(len, fifo->size - (fifo->in & (fifo->size - 1)));
135 memcpy(fifo->buffer + (fifo->in & (fifo->size - 1)), buffer, l);
136
137 /* then put the rest (if any) at the beginning of the buffer */
138 memcpy(fifo->buffer, buffer + l, len - l);
139
Paul E. McKenneya45bce42006-09-29 02:00:11 -0700140 /*
141 * Ensure that we add the bytes to the kfifo -before-
142 * we update the fifo->in index.
143 */
144
145 smp_wmb();
146
Linus Torvalds1da177e2005-04-16 15:20:36 -0700147 fifo->in += len;
148
149 return len;
150}
151EXPORT_SYMBOL(__kfifo_put);
152
153/**
154 * __kfifo_get - gets some data from the FIFO, no locking version
155 * @fifo: the fifo to be used.
156 * @buffer: where the data must be copied.
157 * @len: the size of the destination buffer.
158 *
Robert P. J. Day72fd4a32007-02-10 01:45:59 -0800159 * This function copies at most @len bytes from the FIFO into the
160 * @buffer and returns the number of copied bytes.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700161 *
162 * Note that with only one concurrent reader and one concurrent
163 * writer, you don't need extra locking to use these functions.
164 */
165unsigned int __kfifo_get(struct kfifo *fifo,
166 unsigned char *buffer, unsigned int len)
167{
168 unsigned int l;
169
170 len = min(len, fifo->in - fifo->out);
171
Paul E. McKenneya45bce42006-09-29 02:00:11 -0700172 /*
173 * Ensure that we sample the fifo->in index -before- we
174 * start removing bytes from the kfifo.
175 */
176
177 smp_rmb();
178
Linus Torvalds1da177e2005-04-16 15:20:36 -0700179 /* first get the data from fifo->out until the end of the buffer */
180 l = min(len, fifo->size - (fifo->out & (fifo->size - 1)));
181 memcpy(buffer, fifo->buffer + (fifo->out & (fifo->size - 1)), l);
182
183 /* then get the rest (if any) from the beginning of the buffer */
184 memcpy(buffer + l, fifo->buffer, len - l);
185
Paul E. McKenneya45bce42006-09-29 02:00:11 -0700186 /*
187 * Ensure that we remove the bytes from the kfifo -before-
188 * we update the fifo->out index.
189 */
190
191 smp_mb();
192
Linus Torvalds1da177e2005-04-16 15:20:36 -0700193 fifo->out += len;
194
195 return len;
196}
197EXPORT_SYMBOL(__kfifo_get);