aboutsummaryrefslogtreecommitdiffstats
path: root/kernel/kfifo.c
blob: d659442e73f22cbc1b380bf3b4f33f888a4dc442 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
/*
 * A generic kernel FIFO implementation.
 *
 * Copyright (C) 2009 Stefani Seibold <stefani@seibold.net>
 * Copyright (C) 2004 Stelian Pop <stelian@popies.net>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/err.h>
#include <linux/kfifo.h>
#include <linux/log2.h>

static void _kfifo_init(struct kfifo *fifo, unsigned char *buffer,
		unsigned int size)
{
	fifo->buffer = buffer;
	fifo->size = size;

	kfifo_reset(fifo);
}

/**
 * kfifo_init - initialize a FIFO using a preallocated buffer
 * @fifo: the fifo to assign the buffer
 * @buffer: the preallocated buffer to be used.
 * @size: the size of the internal buffer, this have to be a power of 2.
 *
 */
void kfifo_init(struct kfifo *fifo, unsigned char *buffer, unsigned int size)
{
	/* size must be a power of 2 */
	BUG_ON(!is_power_of_2(size));

	_kfifo_init(fifo, buffer, size);
}
EXPORT_SYMBOL(kfifo_init);

/**
 * kfifo_alloc - allocates a new FIFO internal buffer
 * @fifo: the fifo to assign then new buffer
 * @size: the size of the buffer to be allocated, this have to be a power of 2.
 * @gfp_mask: get_free_pages mask, passed to kmalloc()
 *
 * This function dynamically allocates a new fifo internal buffer
 *
 * The size will be rounded-up to a power of 2.
 * The buffer will be release with kfifo_free().
 * Return 0 if no error, otherwise the an error code
 */
int kfifo_alloc(struct kfifo *fifo, unsigned int size, gfp_t gfp_mask)
{
	unsigned char *buffer;

	/*
	 * round up to the next power of 2, since our 'let the indices
	 * wrap' technique works only in this case.
	 */
	if (!is_power_of_2(size)) {
		BUG_ON(size > 0x80000000);
		size = roundup_pow_of_two(size);
	}

	buffer = kmalloc(size, gfp_mask);
	if (!buffer) {
		_kfifo_init(fifo, 0, 0);
		return -ENOMEM;
	}

	_kfifo_init(fifo, buffer, size);

	return 0;
}
EXPORT_SYMBOL(kfifo_alloc);

/**
 * kfifo_free - frees the FIFO internal buffer
 * @fifo: the fifo to be freed.
 */
void kfifo_free(struct kfifo *fifo)
{
	kfree(fifo->buffer);
}
EXPORT_SYMBOL(kfifo_free);

/**
 * kfifo_in - puts some data into the FIFO
 * @fifo: the fifo to be used.
 * @from: the data to be added.
 * @len: the length of the data to be added.
 *
 * This function copies at most @len bytes from the @from buffer into
 * the FIFO depending on the free space, and returns the number of
 * bytes copied.
 *
 * Note that with only one concurrent reader and one concurrent
 * writer, you don't need extra locking to use these functions.
 */
unsigned int kfifo_in(struct kfifo *fifo,
			const unsigned char *from, unsigned int len)
{
	unsigned int l;

	len = min(len, fifo->size - fifo->in + fifo->out);

	/*
	 * Ensure that we sample the fifo->out index -before- we
	 * start putting bytes into the kfifo.
	 */

	smp_mb();

	/* first put the data starting from fifo->in to buffer end */
	l = min(len, fifo->size - (fifo->in & (fifo->size - 1)));
	memcpy(fifo->buffer + (fifo->in & (fifo->size - 1)), from, l);

	/* then put the rest (if any) at the beginning of the buffer */
	memcpy(fifo->buffer, from + l, len - l);

	/*
	 * Ensure that we add the bytes to the kfifo -before-
	 * we update the fifo->in index.
	 */

	smp_wmb();

	fifo->in += len;

	return len;
}
EXPORT_SYMBOL(kfifo_in);

/**
 * kfifo_out - gets some data from the FIFO
 * @fifo: the fifo to be used.
 * @to: where the data must be copied.
 * @len: the size of the destination buffer.
 *
 * This function copies at most @len bytes from the FIFO into the
 * @to buffer and returns the number of copied bytes.
 *
 * Note that with only one concurrent reader and one concurrent
 * writer, you don't need extra locking to use these functions.
 */
unsigned int kfifo_out(struct kfifo *fifo,
			 unsigned char *to, unsigned int len)
{
	unsigned int l;

	len = min(len, fifo->in - fifo->out);

	/*
	 * Ensure that we sample the fifo->in index -before- we
	 * start removing bytes from the kfifo.
	 */

	smp_rmb();

	/* first get the data from fifo->out until the end of the buffer */
	l = min(len, fifo->size - (fifo->out & (fifo->size - 1)));
	memcpy(to, fifo->buffer + (fifo->out & (fifo->size - 1)), l);

	/* then get the rest (if any) from the beginning of the buffer */
	memcpy(to + l, fifo->buffer, len - l);

	/*
	 * Ensure that we remove the bytes from the kfifo -before-
	 * we update the fifo->out index.
	 */

	smp_mb();

	fifo->out += len;

	return len;
}
EXPORT_SYMBOL(kfifo_out);