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
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 #include <linux/log2.h>
28
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 *
36 * Do NOT pass the kfifo to kfifo_free() after use! Simply free the
37 * &struct kfifo with kfree().
38 */
kfifo_init(unsigned char * buffer,unsigned int size,gfp_t gfp_mask,spinlock_t * lock)39 struct kfifo *kfifo_init(unsigned char *buffer, unsigned int size,
40 gfp_t gfp_mask, spinlock_t *lock)
41 {
42 struct kfifo *fifo;
43
44 /* size must be a power of 2 */
45 BUG_ON(!is_power_of_2(size));
46
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 }
58 EXPORT_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 */
kfifo_alloc(unsigned int size,gfp_t gfp_mask,spinlock_t * lock)68 struct kfifo *kfifo_alloc(unsigned int size, gfp_t gfp_mask, spinlock_t *lock)
69 {
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 }
93 EXPORT_SYMBOL(kfifo_alloc);
94
95 /**
96 * kfifo_free - frees the FIFO
97 * @fifo: the fifo to be freed.
98 */
kfifo_free(struct kfifo * fifo)99 void kfifo_free(struct kfifo *fifo)
100 {
101 kfree(fifo->buffer);
102 kfree(fifo);
103 }
104 EXPORT_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 *
112 * This function copies at most @len bytes from the @buffer into
113 * 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 */
__kfifo_put(struct kfifo * fifo,unsigned char * buffer,unsigned int len)119 unsigned 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
126 /*
127 * Ensure that we sample the fifo->out index -before- we
128 * start putting bytes into the kfifo.
129 */
130
131 smp_mb();
132
133 /* 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
140 /*
141 * Ensure that we add the bytes to the kfifo -before-
142 * we update the fifo->in index.
143 */
144
145 smp_wmb();
146
147 fifo->in += len;
148
149 return len;
150 }
151 EXPORT_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 *
159 * This function copies at most @len bytes from the FIFO into the
160 * @buffer and returns the number of copied bytes.
161 *
162 * Note that with only one concurrent reader and one concurrent
163 * writer, you don't need extra locking to use these functions.
164 */
__kfifo_get(struct kfifo * fifo,unsigned char * buffer,unsigned int len)165 unsigned 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
172 /*
173 * Ensure that we sample the fifo->in index -before- we
174 * start removing bytes from the kfifo.
175 */
176
177 smp_rmb();
178
179 /* 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
186 /*
187 * Ensure that we remove the bytes from the kfifo -before-
188 * we update the fifo->out index.
189 */
190
191 smp_mb();
192
193 fifo->out += len;
194
195 return len;
196 }
197 EXPORT_SYMBOL(__kfifo_get);
198