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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 | */ |
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 | */ |
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' technique works only in this case. |
76 | */ |
77 | if (!is_power_of_2(size)) { |
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 | */ |
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 | */ |
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 | */ |
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 |
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