projects/linux·blob v2.6.21 · refs

196 lines · 5.1 KiB

1/*
2 * A simple kernel FIFO implementation.
3 *
4 * Copyright (C) 2004 Stelian Pop <[email protected]>
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>
27
28/**
29 * kfifo_init - allocates a new FIFO using a preallocated buffer
30 * @buffer: the preallocated buffer to be used.
31 * @size: the size of the internal buffer, this have to be a power of 2.
32 * @gfp_mask: get_free_pages mask, passed to kmalloc()
33 * @lock: the lock to be used to protect the fifo buffer
34 *
35 * Do NOT pass the kfifo to kfifo_free() after use! Simply free the
36 * &struct kfifo with kfree().
37 */
38struct kfifo *kfifo_init(unsigned char *buffer, unsigned int size,
39 gfp_t gfp_mask, spinlock_t *lock)
40{
41 struct kfifo *fifo;
42
43 /* size must be a power of 2 */
44 BUG_ON(size & (size - 1));
45
46 fifo = kmalloc(sizeof(struct kfifo), gfp_mask);
47 if (!fifo)
48 return ERR_PTR(-ENOMEM);
49
50 fifo->buffer = buffer;
51 fifo->size = size;
52 fifo->in = fifo->out = 0;
53 fifo->lock = lock;
54
55 return fifo;
56}
57EXPORT_SYMBOL(kfifo_init);
58
59/**
60 * kfifo_alloc - allocates a new FIFO and its internal buffer
61 * @size: the size of the internal buffer to be allocated.
62 * @gfp_mask: get_free_pages mask, passed to kmalloc()
63 * @lock: the lock to be used to protect the fifo buffer
64 *
65 * The size will be rounded-up to a power of 2.
66 */
67struct kfifo *kfifo_alloc(unsigned int size, gfp_t gfp_mask, spinlock_t *lock)
68{
69 unsigned char *buffer;
70 struct kfifo *ret;
71
72 /*
73 * round up to the next power of 2, since our 'let the indices
74 * wrap' tachnique works only in this case.
75 */
76 if (size & (size - 1)) {
77 BUG_ON(size > 0x80000000);
78 size = roundup_pow_of_two(size);
79 }
80
81 buffer = kmalloc(size, gfp_mask);
82 if (!buffer)
83 return ERR_PTR(-ENOMEM);
84
85 ret = kfifo_init(buffer, size, gfp_mask, lock);
86
87 if (IS_ERR(ret))
88 kfree(buffer);
89
90 return ret;
91}
92EXPORT_SYMBOL(kfifo_alloc);
93
94/**
95 * kfifo_free - frees the FIFO
96 * @fifo: the fifo to be freed.
97 */
98void kfifo_free(struct kfifo *fifo)
99{
100 kfree(fifo->buffer);
101 kfree(fifo);
102}
103EXPORT_SYMBOL(kfifo_free);
104
105/**
106 * __kfifo_put - puts some data into the FIFO, no locking version
107 * @fifo: the fifo to be used.
108 * @buffer: the data to be added.
109 * @len: the length of the data to be added.
110 *
111 * This function copies at most @len bytes from the @buffer into
112 * the FIFO depending on the free space, and returns the number of
113 * bytes copied.
114 *
115 * Note that with only one concurrent reader and one concurrent
116 * writer, you don't need extra locking to use these functions.
117 */
118unsigned int __kfifo_put(struct kfifo *fifo,
119 unsigned char *buffer, unsigned int len)
120{
121 unsigned int l;
122
123 len = min(len, fifo->size - fifo->in + fifo->out);
124
125 /*
126 * Ensure that we sample the fifo->out index -before- we
127 * start putting bytes into the kfifo.
128 */
129
130 smp_mb();
131
132 /* first put the data starting from fifo->in to buffer end */
133 l = min(len, fifo->size - (fifo->in & (fifo->size - 1)));
134 memcpy(fifo->buffer + (fifo->in & (fifo->size - 1)), buffer, l);
135
136 /* then put the rest (if any) at the beginning of the buffer */
137 memcpy(fifo->buffer, buffer + l, len - l);
138
139 /*
140 * Ensure that we add the bytes to the kfifo -before-
141 * we update the fifo->in index.
142 */
143
144 smp_wmb();
145
146 fifo->in += len;
147
148 return len;
149}
150EXPORT_SYMBOL(__kfifo_put);
151
152/**
153 * __kfifo_get - gets some data from the FIFO, no locking version
154 * @fifo: the fifo to be used.
155 * @buffer: where the data must be copied.
156 * @len: the size of the destination buffer.
157 *
158 * This function copies at most @len bytes from the FIFO into the
159 * @buffer and returns the number of copied bytes.
160 *
161 * Note that with only one concurrent reader and one concurrent
162 * writer, you don't need extra locking to use these functions.
163 */
164unsigned int __kfifo_get(struct kfifo *fifo,
165 unsigned char *buffer, unsigned int len)
166{
167 unsigned int l;
168
169 len = min(len, fifo->in - fifo->out);
170
171 /*
172 * Ensure that we sample the fifo->in index -before- we
173 * start removing bytes from the kfifo.
174 */
175
176 smp_rmb();
177
178 /* first get the data from fifo->out until the end of the buffer */
179 l = min(len, fifo->size - (fifo->out & (fifo->size - 1)));
180 memcpy(buffer, fifo->buffer + (fifo->out & (fifo->size - 1)), l);
181
182 /* then get the rest (if any) from the beginning of the buffer */
183 memcpy(buffer + l, fifo->buffer, len - l);
184
185 /*
186 * Ensure that we remove the bytes from the kfifo -before-
187 * we update the fifo->out index.
188 */
189
190 smp_mb();
191
192 fifo->out += len;
193
194 return len;
195}
196EXPORT_SYMBOL(__kfifo_get);