1 /* 2 * Sample kfifo int type 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 int type fifo. 18 */ 19 20 /* fifo size in elements (ints) */ 21 #define FIFO_SIZE 32 22 23 /* name of the proc entry */ 24 #define PROC_FIFO "int-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 DECLARE_KFIFO_PTR(test, int); 43 #else 44 static DEFINE_KFIFO(test, int, FIFO_SIZE); 45 #endif 46 47 static const int 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 int buf[6]; 57 int i, j; 58 unsigned int ret; 59 60 printk(KERN_INFO "int fifo test start\n"); 61 62 /* put values into the fifo */ 63 for (i = 0; i != 10; i++) 64 kfifo_put(&test, i); 65 66 /* show the number of used elements */ 67 printk(KERN_INFO "fifo len: %u\n", kfifo_len(&test)); 68 69 /* get max of 2 elements from the fifo */ 70 ret = kfifo_out(&test, buf, 2); 71 printk(KERN_INFO "ret: %d\n", ret); 72 /* and put it back to the end of the fifo */ 73 ret = kfifo_in(&test, buf, ret); 74 printk(KERN_INFO "ret: %d\n", ret); 75 76 /* skip first element of the fifo */ 77 printk(KERN_INFO "skip 1st element\n"); 78 kfifo_skip(&test); 79 80 /* put values into the fifo until is full */ 81 for (i = 20; kfifo_put(&test, i); i++) 82 ; 83 84 printk(KERN_INFO "queue len: %u\n", kfifo_len(&test)); 85 86 /* show the first value without removing from the fifo */ 87 if (kfifo_peek(&test, &i)) 88 printk(KERN_INFO "%d\n", i); 89 90 /* check the correctness of all values in the fifo */ 91 j = 0; 92 while (kfifo_get(&test, &i)) { 93 printk(KERN_INFO "item = %d\n", i); 94 if (i != expected_result[j++]) { 95 printk(KERN_WARNING "value mismatch: test failed\n"); 96 return -EIO; 97 } 98 } 99 if (j != ARRAY_SIZE(expected_result)) { 100 printk(KERN_WARNING "size mismatch: test failed\n"); 101 return -EIO; 102 } 103 printk(KERN_INFO "test passed\n"); 104 105 return 0; 106 } 107 108 static ssize_t fifo_write(struct file *file, const char __user *buf, 109 size_t count, loff_t *ppos) 110 { 111 int ret; 112 unsigned int copied; 113 114 if (mutex_lock_interruptible(&write_lock)) 115 return -ERESTARTSYS; 116 117 ret = kfifo_from_user(&test, buf, count, &copied); 118 119 mutex_unlock(&write_lock); 120 121 return ret ? ret : copied; 122 } 123 124 static ssize_t fifo_read(struct file *file, char __user *buf, 125 size_t count, loff_t *ppos) 126 { 127 int ret; 128 unsigned int copied; 129 130 if (mutex_lock_interruptible(&read_lock)) 131 return -ERESTARTSYS; 132 133 ret = kfifo_to_user(&test, buf, count, &copied); 134 135 mutex_unlock(&read_lock); 136 137 return ret ? ret : copied; 138 } 139 140 static const struct file_operations fifo_fops = { 141 .owner = THIS_MODULE, 142 .read = fifo_read, 143 .write = fifo_write, 144 .llseek = noop_llseek, 145 }; 146 147 static int __init example_init(void) 148 { 149 #ifdef DYNAMIC 150 int ret; 151 152 ret = kfifo_alloc(&test, FIFO_SIZE, GFP_KERNEL); 153 if (ret) { 154 printk(KERN_ERR "error kfifo_alloc\n"); 155 return ret; 156 } 157 #endif 158 if (testfunc() < 0) { 159 #ifdef DYNAMIC 160 kfifo_free(&test); 161 #endif 162 return -EIO; 163 } 164 165 if (proc_create(PROC_FIFO, 0, NULL, &fifo_fops) == NULL) { 166 #ifdef DYNAMIC 167 kfifo_free(&test); 168 #endif 169 return -ENOMEM; 170 } 171 return 0; 172 } 173 174 static void __exit example_exit(void) 175 { 176 remove_proc_entry(PROC_FIFO, NULL); 177 #ifdef DYNAMIC 178 kfifo_free(&test); 179 #endif 180 } 181 182 module_init(example_init); 183 module_exit(example_exit); 184 MODULE_LICENSE("GPL"); 185 MODULE_AUTHOR("Stefani Seibold <stefani@seibold.net>"); 186