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 const char *expected_result[] = { 59 "a", 60 "bb", 61 "ccc", 62 "dddd", 63 "eeeee", 64 "ffffff", 65 "ggggggg", 66 "hhhhhhhh", 67 "iiiiiiiii", 68 "jjjjjjjjjj", 69 }; 70 71 static int __init testfunc(void) 72 { 73 char buf[100]; 74 unsigned int i; 75 unsigned int ret; 76 struct { unsigned char buf[6]; } hello = { "hello" }; 77 78 printk(KERN_INFO "record fifo test start\n"); 79 80 kfifo_in(&test, &hello, sizeof(hello)); 81 82 /* show the size of the next record in the fifo */ 83 printk(KERN_INFO "fifo peek len: %u\n", kfifo_peek_len(&test)); 84 85 /* put in variable length data */ 86 for (i = 0; i < 10; i++) { 87 memset(buf, 'a' + i, i + 1); 88 kfifo_in(&test, buf, i + 1); 89 } 90 91 /* skip first element of the fifo */ 92 printk(KERN_INFO "skip 1st element\n"); 93 kfifo_skip(&test); 94 95 printk(KERN_INFO "fifo len: %u\n", kfifo_len(&test)); 96 97 /* show the first record without removing from the fifo */ 98 ret = kfifo_out_peek(&test, buf, sizeof(buf)); 99 if (ret) 100 printk(KERN_INFO "%.*s\n", ret, buf); 101 102 /* check the correctness of all values in the fifo */ 103 i = 0; 104 while (!kfifo_is_empty(&test)) { 105 ret = kfifo_out(&test, buf, sizeof(buf)); 106 buf[ret] = '\0'; 107 printk(KERN_INFO "item = %.*s\n", ret, buf); 108 if (strcmp(buf, expected_result[i++])) { 109 printk(KERN_WARNING "value mismatch: test failed\n"); 110 return -EIO; 111 } 112 } 113 if (i != ARRAY_SIZE(expected_result)) { 114 printk(KERN_WARNING "size mismatch: test failed\n"); 115 return -EIO; 116 } 117 printk(KERN_INFO "test passed\n"); 118 119 return 0; 120 } 121 122 static ssize_t fifo_write(struct file *file, const char __user *buf, 123 size_t count, loff_t *ppos) 124 { 125 int ret; 126 unsigned int copied; 127 128 if (mutex_lock_interruptible(&write_lock)) 129 return -ERESTARTSYS; 130 131 ret = kfifo_from_user(&test, buf, count, &copied); 132 133 mutex_unlock(&write_lock); 134 135 return ret ? ret : copied; 136 } 137 138 static ssize_t fifo_read(struct file *file, char __user *buf, 139 size_t count, loff_t *ppos) 140 { 141 int ret; 142 unsigned int copied; 143 144 if (mutex_lock_interruptible(&read_lock)) 145 return -ERESTARTSYS; 146 147 ret = kfifo_to_user(&test, buf, count, &copied); 148 149 mutex_unlock(&read_lock); 150 151 return ret ? ret : copied; 152 } 153 154 static const struct file_operations fifo_fops = { 155 .owner = THIS_MODULE, 156 .read = fifo_read, 157 .write = fifo_write, 158 .llseek = noop_llseek, 159 }; 160 161 static int __init example_init(void) 162 { 163 #ifdef DYNAMIC 164 int ret; 165 166 ret = kfifo_alloc(&test, FIFO_SIZE, GFP_KERNEL); 167 if (ret) { 168 printk(KERN_ERR "error kfifo_alloc\n"); 169 return ret; 170 } 171 #else 172 INIT_KFIFO(test); 173 #endif 174 if (testfunc() < 0) { 175 #ifdef DYNAMIC 176 kfifo_free(&test); 177 #endif 178 return -EIO; 179 } 180 181 if (proc_create(PROC_FIFO, 0, NULL, &fifo_fops) == NULL) { 182 #ifdef DYNAMIC 183 kfifo_free(&test); 184 #endif 185 return -ENOMEM; 186 } 187 return 0; 188 } 189 190 static void __exit example_exit(void) 191 { 192 remove_proc_entry(PROC_FIFO, NULL); 193 #ifdef DYNAMIC 194 kfifo_free(&test); 195 #endif 196 } 197 198 module_init(example_init); 199 module_exit(example_exit); 200 MODULE_LICENSE("GPL"); 201 MODULE_AUTHOR("Stefani Seibold <stefani@seibold.net>"); 202