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5bf2b193 SS |
1 | /* |
2 | * Sample dynamic sized record fifo implementation | |
3 | * | |
4 | * Copyright (C) 2010 Stefani Seibold <stefani@seibold.net> | |
5 | * | |
6 | * Released under the GPL version 2 only. | |
7 | * | |
8 | */ | |
9 | ||
10 | #include <linux/init.h> | |
11 | #include <linux/module.h> | |
12 | #include <linux/proc_fs.h> | |
13 | #include <linux/mutex.h> | |
14 | #include <linux/kfifo.h> | |
15 | ||
16 | /* | |
17 | * This module shows how to create a variable sized record fifo. | |
18 | */ | |
19 | ||
20 | /* fifo size in elements (bytes) */ | |
21 | #define FIFO_SIZE 128 | |
22 | ||
23 | /* name of the proc entry */ | |
24 | #define PROC_FIFO "record-fifo" | |
25 | ||
26 | /* lock for procfs read access */ | |
27 | static DEFINE_MUTEX(read_lock); | |
28 | ||
29 | /* lock for procfs write access */ | |
30 | static DEFINE_MUTEX(write_lock); | |
31 | ||
32 | /* | |
33 | * define DYNAMIC in this example for a dynamically allocated fifo. | |
34 | * | |
35 | * Otherwise the fifo storage will be a part of the fifo structure. | |
36 | */ | |
37 | #if 0 | |
38 | #define DYNAMIC | |
39 | #endif | |
40 | ||
41 | /* | |
42 | * struct kfifo_rec_ptr_1 and STRUCT_KFIFO_REC_1 can handle records of a | |
43 | * length between 0 and 255 bytes. | |
44 | * | |
45 | * struct kfifo_rec_ptr_2 and STRUCT_KFIFO_REC_2 can handle records of a | |
46 | * length between 0 and 65535 bytes. | |
47 | */ | |
48 | ||
49 | #ifdef DYNAMIC | |
50 | struct kfifo_rec_ptr_1 test; | |
51 | ||
52 | #else | |
53 | typedef STRUCT_KFIFO_REC_1(FIFO_SIZE) mytest; | |
54 | ||
55 | static mytest test; | |
56 | #endif | |
57 | ||
58 | static int __init testfunc(void) | |
59 | { | |
60 | char buf[100]; | |
61 | unsigned int i; | |
62 | unsigned int ret; | |
63 | struct { unsigned char buf[6]; } hello = { "hello" }; | |
64 | ||
65 | printk(KERN_INFO "record fifo test start\n"); | |
66 | ||
67 | kfifo_in(&test, &hello, sizeof(hello)); | |
68 | ||
69 | /* show the size of the next record in the fifo */ | |
70 | printk(KERN_INFO "fifo peek len: %u\n", kfifo_peek_len(&test)); | |
71 | ||
72 | /* put in variable length data */ | |
73 | for (i = 0; i < 10; i++) { | |
74 | memset(buf, 'a' + i, i + 1); | |
75 | kfifo_in(&test, buf, i + 1); | |
76 | } | |
77 | ||
78 | printk(KERN_INFO "fifo len: %u\n", kfifo_len(&test)); | |
79 | ||
80 | /* show the first record without removing from the fifo */ | |
81 | ret = kfifo_out_peek(&test, buf, sizeof(buf)); | |
82 | if (ret) | |
83 | printk(KERN_INFO "%.*s\n", ret, buf); | |
84 | ||
85 | /* print out all records in the fifo */ | |
86 | while (!kfifo_is_empty(&test)) { | |
87 | ret = kfifo_out(&test, buf, sizeof(buf)); | |
88 | printk(KERN_INFO "%.*s\n", ret, buf); | |
89 | } | |
90 | ||
91 | return 0; | |
92 | } | |
93 | ||
94 | static ssize_t fifo_write(struct file *file, const char __user *buf, | |
95 | size_t count, loff_t *ppos) | |
96 | { | |
97 | int ret; | |
98 | unsigned int copied; | |
99 | ||
100 | if (mutex_lock_interruptible(&write_lock)) | |
101 | return -ERESTARTSYS; | |
102 | ||
103 | ret = kfifo_from_user(&test, buf, count, &copied); | |
104 | ||
105 | mutex_unlock(&write_lock); | |
106 | ||
107 | return ret ? ret : copied; | |
108 | } | |
109 | ||
110 | static ssize_t fifo_read(struct file *file, char __user *buf, | |
111 | size_t count, loff_t *ppos) | |
112 | { | |
113 | int ret; | |
114 | unsigned int copied; | |
115 | ||
116 | if (mutex_lock_interruptible(&read_lock)) | |
117 | return -ERESTARTSYS; | |
118 | ||
119 | ret = kfifo_to_user(&test, buf, count, &copied); | |
120 | ||
121 | mutex_unlock(&read_lock); | |
122 | ||
123 | return ret ? ret : copied; | |
124 | } | |
125 | ||
126 | static const struct file_operations fifo_fops = { | |
127 | .owner = THIS_MODULE, | |
128 | .read = fifo_read, | |
129 | .write = fifo_write, | |
130 | }; | |
131 | ||
132 | static int __init example_init(void) | |
133 | { | |
134 | #ifdef DYNAMIC | |
135 | int ret; | |
136 | ||
137 | ret = kfifo_alloc(&test, FIFO_SIZE, GFP_KERNEL); | |
138 | if (ret) { | |
139 | printk(KERN_ERR "error kfifo_alloc\n"); | |
140 | return ret; | |
141 | } | |
142 | #else | |
143 | INIT_KFIFO(test); | |
144 | #endif | |
145 | testfunc(); | |
146 | ||
147 | if (proc_create(PROC_FIFO, 0, NULL, &fifo_fops) == NULL) { | |
148 | #ifdef DYNAMIC | |
149 | kfifo_free(&test); | |
150 | #endif | |
151 | return -ENOMEM; | |
152 | } | |
153 | return 0; | |
154 | } | |
155 | ||
156 | static void __exit example_exit(void) | |
157 | { | |
158 | remove_proc_entry(PROC_FIFO, NULL); | |
159 | #ifdef DYNAMIC | |
160 | kfifo_free(&test); | |
161 | #endif | |
162 | } | |
163 | ||
164 | module_init(example_init); | |
165 | module_exit(example_exit); | |
166 | MODULE_LICENSE("GPL"); | |
167 | MODULE_AUTHOR("Stefani Seibold <stefani@seibold.net>"); |