2 * A simple kernel FIFO implementation.
4 * Copyright (C) 2004 Stelian Pop <stelian@popies.net>
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.
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.
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.
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>
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
35 * Do NOT pass the kfifo to kfifo_free() after use ! Simply free the
36 * struct kfifo with kfree().
38 struct kfifo
*kfifo_init(unsigned char *buffer
, unsigned int size
,
39 gfp_t gfp_mask
, spinlock_t
*lock
)
43 /* size must be a power of 2 */
44 BUG_ON(size
& (size
- 1));
46 fifo
= kmalloc(sizeof(struct kfifo
), gfp_mask
);
48 return ERR_PTR(-ENOMEM
);
50 fifo
->buffer
= buffer
;
52 fifo
->in
= fifo
->out
= 0;
57 EXPORT_SYMBOL(kfifo_init
);
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
65 * The size will be rounded-up to a power of 2.
67 struct kfifo
*kfifo_alloc(unsigned int size
, gfp_t gfp_mask
, spinlock_t
*lock
)
69 unsigned char *buffer
;
73 * round up to the next power of 2, since our 'let the indices
74 * wrap' tachnique works only in this case.
76 if (size
& (size
- 1)) {
77 BUG_ON(size
> 0x80000000);
78 size
= roundup_pow_of_two(size
);
81 buffer
= kmalloc(size
, gfp_mask
);
83 return ERR_PTR(-ENOMEM
);
85 ret
= kfifo_init(buffer
, size
, gfp_mask
, lock
);
92 EXPORT_SYMBOL(kfifo_alloc
);
95 * kfifo_free - frees the FIFO
96 * @fifo: the fifo to be freed.
98 void kfifo_free(struct kfifo
*fifo
)
103 EXPORT_SYMBOL(kfifo_free
);
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.
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
115 * Note that with only one concurrent reader and one concurrent
116 * writer, you don't need extra locking to use these functions.
118 unsigned int __kfifo_put(struct kfifo
*fifo
,
119 unsigned char *buffer
, unsigned int len
)
123 len
= min(len
, fifo
->size
- fifo
->in
+ fifo
->out
);
126 * Ensure that we sample the fifo->out index -before- we
127 * start putting bytes into the kfifo.
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
);
136 /* then put the rest (if any) at the beginning of the buffer */
137 memcpy(fifo
->buffer
, buffer
+ l
, len
- l
);
140 * Ensure that we add the bytes to the kfifo -before-
141 * we update the fifo->in index.
150 EXPORT_SYMBOL(__kfifo_put
);
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.
158 * This function copies at most 'len' bytes from the FIFO into the
159 * 'buffer' and returns the number of copied bytes.
161 * Note that with only one concurrent reader and one concurrent
162 * writer, you don't need extra locking to use these functions.
164 unsigned int __kfifo_get(struct kfifo
*fifo
,
165 unsigned char *buffer
, unsigned int len
)
169 len
= min(len
, fifo
->in
- fifo
->out
);
172 * Ensure that we sample the fifo->in index -before- we
173 * start removing bytes from the kfifo.
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
);
182 /* then get the rest (if any) from the beginning of the buffer */
183 memcpy(buffer
+ l
, fifo
->buffer
, len
- l
);
186 * Ensure that we remove the bytes from the kfifo -before-
187 * we update the fifo->out index.
196 EXPORT_SYMBOL(__kfifo_get
);
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