1 /* 2 * Sample kfifo byte stream 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 byte stream fifo. 18 */ 19 20 /* fifo size in elements (bytes) */ 21 #define FIFO_SIZE 32 22 23 /* name of the proc entry */ 24 #define PROC_FIFO "bytestream-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 #ifdef DYNAMIC 42 static struct kfifo test; 43 #else 44 static DECLARE_KFIFO(test, unsigned char, FIFO_SIZE); 45 #endif 46 47 static unsigned char expected_result[FIFO_SIZE] = { 48 3, 4, 5, 6, 7, 8, 9, 0, 49 1, 20, 21, 22, 23, 24, 25, 26, 50 27, 28, 29, 30, 31, 32, 33, 34, 51 35, 36, 37, 38, 39, 40, 41, 42, 52 }; 53 54 static int __init testfunc(void) 55 { 56 unsigned char buf[6]; 57 unsigned char i, j; 58 unsigned int ret; 59 60 printk(KERN_INFO "byte stream fifo test start\n"); 61 62 /* put string into the fifo */ 63 kfifo_in(&test, "hello", 5); 64 65 /* put values into the fifo */ 66 for (i = 0; i != 10; i++) 67 kfifo_put(&test, &i); 68 69 /* show the number of used elements */ 70 printk(KERN_INFO "fifo len: %u\n", kfifo_len(&test)); 71 72 /* get max of 5 bytes from the fifo */ 73 i = kfifo_out(&test, buf, 5); 74 printk(KERN_INFO "buf: %.*s\n", i, buf); 75 76 /* get max of 2 elements from the fifo */ 77 ret = kfifo_out(&test, buf, 2); 78 printk(KERN_INFO "ret: %d\n", ret); 79 /* and put it back to the end of the fifo */ 80 ret = kfifo_in(&test, buf, ret); 81 printk(KERN_INFO "ret: %d\n", ret); 82 83 /* skip first element of the fifo */ 84 printk(KERN_INFO "skip 1st element\n"); 85 kfifo_skip(&test); 86 87 /* put values into the fifo until is full */ 88 for (i = 20; kfifo_put(&test, &i); i++) 89 ; 90 91 printk(KERN_INFO "queue len: %u\n", kfifo_len(&test)); 92 93 /* check the correctness of all values in the fifo */ 94 j = 0; 95 while (kfifo_get(&test, &i)) { 96 if (i != expected_result[j++]) { 97 printk(KERN_WARNING "value mismatch: test failed\n"); 98 return -EIO; 99 } 100 } 101 if (j != ARRAY_SIZE(expected_result)) { 102 printk(KERN_WARNING "size mismatch: test failed\n"); 103 return -EIO; 104 } 105 printk(KERN_INFO "test passed\n"); 106 107 return 0; 108 } 109 110 static ssize_t fifo_write(struct file *file, const char __user *buf, 111 size_t count, loff_t *ppos) 112 { 113 int ret; 114 unsigned int copied; 115 116 if (mutex_lock_interruptible(&write_lock)) 117 return -ERESTARTSYS; 118 119 ret = kfifo_from_user(&test, buf, count, &copied); 120 121 mutex_unlock(&write_lock); 122 123 return ret ? ret : copied; 124 } 125 126 static ssize_t fifo_read(struct file *file, char __user *buf, 127 size_t count, loff_t *ppos) 128 { 129 int ret; 130 unsigned int copied; 131 132 if (mutex_lock_interruptible(&read_lock)) 133 return -ERESTARTSYS; 134 135 ret = kfifo_to_user(&test, buf, count, &copied); 136 137 mutex_unlock(&read_lock); 138 139 return ret ? ret : copied; 140 } 141 142 static const struct file_operations fifo_fops = { 143 .owner = THIS_MODULE, 144 .read = fifo_read, 145 .write = fifo_write, 146 }; 147 148 static int __init example_init(void) 149 { 150 #ifdef DYNAMIC 151 int ret; 152 153 ret = kfifo_alloc(&test, FIFO_SIZE, GFP_KERNEL); 154 if (ret) { 155 printk(KERN_ERR "error kfifo_alloc\n"); 156 return ret; 157 } 158 #else 159 INIT_KFIFO(test); 160 #endif 161 if (testfunc() < 0) { 162 #ifdef DYNAMIC 163 kfifo_free(&test); 164 #endif 165 return -EIO; 166 } 167 168 if (proc_create(PROC_FIFO, 0, NULL, &fifo_fops) == NULL) { 169 #ifdef DYNAMIC 170 kfifo_free(&test); 171 #endif 172 return -ENOMEM; 173 } 174 return 0; 175 } 176 177 static void __exit example_exit(void) 178 { 179 remove_proc_entry(PROC_FIFO, NULL); 180 #ifdef DYNAMIC 181 kfifo_free(&test); 182 #endif 183 } 184 185 module_init(example_init); 186 module_exit(example_exit); 187 MODULE_LICENSE("GPL"); 188 MODULE_AUTHOR("Stefani Seibold <stefani@seibold.net>"); 189