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 */ 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 DECLARE_KFIFO_PTR(test, int); 40#else 41static DEFINE_KFIFO(test, int, FIFO_SIZE); 42#endif 43 44static const int 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 int buf[6]; 54 int i, j; 55 unsigned int ret; 56 57 printk(KERN_INFO "int fifo test start\n"); 58 59 /* put values into the fifo */ 60 for (i = 0; i != 10; i++) 61 kfifo_put(&test, &i); 62 63 /* show the number of used elements */ 64 printk(KERN_INFO "fifo len: %u\n", kfifo_len(&test)); 65 66 /* get max of 2 elements from the fifo */ 67 ret = kfifo_out(&test, buf, 2); 68 printk(KERN_INFO "ret: %d\n", ret); 69 /* and put it back to the end of the fifo */ 70 ret = kfifo_in(&test, buf, ret); 71 printk(KERN_INFO "ret: %d\n", ret); 72 73 /* skip first element of the fifo */ 74 printk(KERN_INFO "skip 1st element\n"); 75 kfifo_skip(&test); 76 77 /* put values into the fifo until is full */ 78 for (i = 20; kfifo_put(&test, &i); i++) 79 ; 80 81 printk(KERN_INFO "queue len: %u\n", kfifo_len(&test)); 82 83 /* show the first value without removing from the fifo */ 84 if (kfifo_peek(&test, &i)) 85 printk(KERN_INFO "%d\n", i); 86 87 /* check the correctness of all values in the fifo */ 88 j = 0; 89 while (kfifo_get(&test, &i)) { 90 printk(KERN_INFO "item = %d\n", i); 91 if (i != expected_result[j++]) { 92 printk(KERN_WARNING "value mismatch: test failed\n"); 93 return -EIO; 94 } 95 } 96 if (j != ARRAY_SIZE(expected_result)) { 97 printk(KERN_WARNING "size mismatch: test failed\n"); 98 return -EIO; 99 } 100 printk(KERN_INFO "test passed\n"); 101 102 return 0; 103} 104 105static ssize_t fifo_write(struct file *file, const char __user *buf, 106 size_t count, loff_t *ppos) 107{ 108 int ret; 109 unsigned int copied; 110 111 if (mutex_lock_interruptible(&write_lock)) 112 return -ERESTARTSYS; 113 114 ret = kfifo_from_user(&test, buf, count, &copied); 115 116 mutex_unlock(&write_lock); 117 118 return ret ? ret : copied; 119} 120 121static ssize_t fifo_read(struct file *file, char __user *buf, 122 size_t count, loff_t *ppos) 123{ 124 int ret; 125 unsigned int copied; 126 127 if (mutex_lock_interruptible(&read_lock)) 128 return -ERESTARTSYS; 129 130 ret = kfifo_to_user(&test, buf, count, &copied); 131 132 mutex_unlock(&read_lock); 133 134 return ret ? ret : copied; 135} 136 137static const struct file_operations fifo_fops = { 138 .owner = THIS_MODULE, 139 .read = fifo_read, 140 .write = fifo_write, 141}; 142 143static int __init example_init(void) 144{ 145#ifdef DYNAMIC 146 int ret; 147 148 ret = kfifo_alloc(&test, FIFO_SIZE, GFP_KERNEL); 149 if (ret) { 150 printk(KERN_ERR "error kfifo_alloc\n"); 151 return ret; 152 } 153#endif 154 if (testfunc() < 0) { 155#ifdef DYNAMIC 156 kfifo_free(&test); 157#endif 158 return -EIO; 159 } 160 161 if (proc_create(PROC_FIFO, 0, NULL, &fifo_fops) == NULL) { 162#ifdef DYNAMIC 163 kfifo_free(&test); 164#endif 165 return -ENOMEM; 166 } 167 return 0; 168} 169 170static void __exit example_exit(void) 171{ 172 remove_proc_entry(PROC_FIFO, NULL); 173#ifdef DYNAMIC 174 kfifo_free(&test); 175#endif 176} 177 178module_init(example_init); 179module_exit(example_exit); 180MODULE_LICENSE("GPL"); 181MODULE_AUTHOR("Stefani Seibold <stefani@seibold.net>"); 182