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 */ 27static DEFINE_MUTEX(read_lock); 28 29/* lock for procfs write access */ 30static 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 38#ifdef DYNAMIC 39static struct kfifo test; 40#else 41static DECLARE_KFIFO(test, unsigned char, FIFO_SIZE); 42#endif 43 44static const unsigned char expected_result[FIFO_SIZE] = { 45 3, 4, 5, 6, 7, 8, 9, 0, 46 1, 20, 21, 22, 23, 24, 25, 26, 47 27, 28, 29, 30, 31, 32, 33, 34, 48 35, 36, 37, 38, 39, 40, 41, 42, 49}; 50 51static int __init testfunc(void) 52{ 53 unsigned char buf[6]; 54 unsigned char i, j; 55 unsigned int ret; 56 57 printk(KERN_INFO "byte stream fifo test start\n"); 58 59 /* put string into the fifo */ 60 kfifo_in(&test, "hello", 5); 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 5 bytes from the fifo */ 70 i = kfifo_out(&test, buf, 5); 71 printk(KERN_INFO "buf: %.*s\n", i, buf); 72 73 /* get max of 2 elements from the fifo */ 74 ret = kfifo_out(&test, buf, 2); 75 printk(KERN_INFO "ret: %d\n", ret); 76 /* and put it back to the end of the fifo */ 77 ret = kfifo_in(&test, buf, ret); 78 printk(KERN_INFO "ret: %d\n", ret); 79 80 /* skip first element of the fifo */ 81 printk(KERN_INFO "skip 1st element\n"); 82 kfifo_skip(&test); 83 84 /* put values into the fifo until is full */ 85 for (i = 20; kfifo_put(&test, &i); i++) 86 ; 87 88 printk(KERN_INFO "queue len: %u\n", kfifo_len(&test)); 89 90 /* show the first value without removing from the fifo */ 91 if (kfifo_peek(&test, &i)) 92 printk(KERN_INFO "%d\n", i); 93 94 /* check the correctness of all values in the fifo */ 95 j = 0; 96 while (kfifo_get(&test, &i)) { 97 printk(KERN_INFO "item = %d\n", i); 98 if (i != expected_result[j++]) { 99 printk(KERN_WARNING "value mismatch: test failed\n"); 100 return -EIO; 101 } 102 } 103 if (j != ARRAY_SIZE(expected_result)) { 104 printk(KERN_WARNING "size mismatch: test failed\n"); 105 return -EIO; 106 } 107 printk(KERN_INFO "test passed\n"); 108 109 return 0; 110} 111 112static ssize_t fifo_write(struct file *file, const char __user *buf, 113 size_t count, loff_t *ppos) 114{ 115 int ret; 116 unsigned int copied; 117 118 if (mutex_lock_interruptible(&write_lock)) 119 return -ERESTARTSYS; 120 121 ret = kfifo_from_user(&test, buf, count, &copied); 122 123 mutex_unlock(&write_lock); 124 125 return ret ? ret : copied; 126} 127 128static ssize_t fifo_read(struct file *file, char __user *buf, 129 size_t count, loff_t *ppos) 130{ 131 int ret; 132 unsigned int copied; 133 134 if (mutex_lock_interruptible(&read_lock)) 135 return -ERESTARTSYS; 136 137 ret = kfifo_to_user(&test, buf, count, &copied); 138 139 mutex_unlock(&read_lock); 140 141 return ret ? ret : copied; 142} 143 144static const struct file_operations fifo_fops = { 145 .owner = THIS_MODULE, 146 .read = fifo_read, 147 .write = fifo_write, 148}; 149 150static int __init example_init(void) 151{ 152#ifdef DYNAMIC 153 int ret; 154 155 ret = kfifo_alloc(&test, FIFO_SIZE, GFP_KERNEL); 156 if (ret) { 157 printk(KERN_ERR "error kfifo_alloc\n"); 158 return ret; 159 } 160#else 161 INIT_KFIFO(test); 162#endif 163 if (testfunc() < 0) { 164#ifdef DYNAMIC 165 kfifo_free(&test); 166#endif 167 return -EIO; 168 } 169 170 if (proc_create(PROC_FIFO, 0, NULL, &fifo_fops) == NULL) { 171#ifdef DYNAMIC 172 kfifo_free(&test); 173#endif 174 return -ENOMEM; 175 } 176 return 0; 177} 178 179static void __exit example_exit(void) 180{ 181 remove_proc_entry(PROC_FIFO, NULL); 182#ifdef DYNAMIC 183 kfifo_free(&test); 184#endif 185} 186 187module_init(example_init); 188module_exit(example_exit); 189MODULE_LICENSE("GPL"); 190MODULE_AUTHOR("Stefani Seibold <stefani@seibold.net>"); 191