Contents of /alx-src/tags/kernel26-2.6.12-alx-r9/kernel/kfifo.c
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Wed Mar 4 11:03:09 2009 UTC (15 years, 6 months ago) by niro
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Wed Mar 4 11:03:09 2009 UTC (15 years, 6 months ago) by niro
File MIME type: text/plain
File size: 4764 byte(s)
Tag kernel26-2.6.12-alx-r9
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 | |
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 | */ |
38 | struct kfifo *kfifo_init(unsigned char *buffer, unsigned int size, |
39 | unsigned int __nocast 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 | } |
57 | EXPORT_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 | */ |
67 | struct kfifo *kfifo_alloc(unsigned int size, unsigned int __nocast 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 | } |
92 | EXPORT_SYMBOL(kfifo_alloc); |
93 | |
94 | /** |
95 | * kfifo_free - frees the FIFO |
96 | * @fifo: the fifo to be freed. |
97 | */ |
98 | void kfifo_free(struct kfifo *fifo) |
99 | { |
100 | kfree(fifo->buffer); |
101 | kfree(fifo); |
102 | } |
103 | EXPORT_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 | */ |
118 | unsigned 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 | /* first put the data starting from fifo->in to buffer end */ |
126 | l = min(len, fifo->size - (fifo->in & (fifo->size - 1))); |
127 | memcpy(fifo->buffer + (fifo->in & (fifo->size - 1)), buffer, l); |
128 | |
129 | /* then put the rest (if any) at the beginning of the buffer */ |
130 | memcpy(fifo->buffer, buffer + l, len - l); |
131 | |
132 | fifo->in += len; |
133 | |
134 | return len; |
135 | } |
136 | EXPORT_SYMBOL(__kfifo_put); |
137 | |
138 | /** |
139 | * __kfifo_get - gets some data from the FIFO, no locking version |
140 | * @fifo: the fifo to be used. |
141 | * @buffer: where the data must be copied. |
142 | * @len: the size of the destination buffer. |
143 | * |
144 | * This function copies at most 'len' bytes from the FIFO into the |
145 | * 'buffer' and returns the number of copied bytes. |
146 | * |
147 | * Note that with only one concurrent reader and one concurrent |
148 | * writer, you don't need extra locking to use these functions. |
149 | */ |
150 | unsigned int __kfifo_get(struct kfifo *fifo, |
151 | unsigned char *buffer, unsigned int len) |
152 | { |
153 | unsigned int l; |
154 | |
155 | len = min(len, fifo->in - fifo->out); |
156 | |
157 | /* first get the data from fifo->out until the end of the buffer */ |
158 | l = min(len, fifo->size - (fifo->out & (fifo->size - 1))); |
159 | memcpy(buffer, fifo->buffer + (fifo->out & (fifo->size - 1)), l); |
160 | |
161 | /* then get the rest (if any) from the beginning of the buffer */ |
162 | memcpy(buffer + l, fifo->buffer, len - l); |
163 | |
164 | fifo->out += len; |
165 | |
166 | return len; |
167 | } |
168 | EXPORT_SYMBOL(__kfifo_get); |