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 int __init testfunc(void) 48 { 49 int buf[6]; 50 int i; 51 unsigned int ret; 52 53 printk(KERN_INFO "int fifo test start\n"); 54 55 /* put values into the fifo */ 56 for (i = 0; i != 10; i++) 57 kfifo_put(&test, &i); 58 59 /* show the number of used elements */ 60 printk(KERN_INFO "fifo len: %u\n", kfifo_len(&test)); 61 62 /* get max of 2 elements from the fifo */ 63 ret = kfifo_out(&test, buf, 2); 64 printk(KERN_INFO "ret: %d\n", ret); 65 /* and put it back to the end of the fifo */ 66 ret = kfifo_in(&test, buf, ret); 67 printk(KERN_INFO "ret: %d\n", ret); 68 69 for (i = 20; i != 30; i++) 70 kfifo_put(&test, &i); 71 72 printk(KERN_INFO "queue len: %u\n", kfifo_len(&test)); 73 74 /* show the first value without removing from the fifo */ 75 if (kfifo_peek(&test, &i)) 76 printk(KERN_INFO "%d\n", i); 77 78 /* print out all values in the fifo */ 79 while (kfifo_get(&test, &i)) 80 printk("%d ", i); 81 printk("\n"); 82 83 return 0; 84 } 85 86 static ssize_t fifo_write(struct file *file, const char __user *buf, 87 size_t count, loff_t *ppos) 88 { 89 int ret; 90 unsigned int copied; 91 92 if (mutex_lock_interruptible(&write_lock)) 93 return -ERESTARTSYS; 94 95 ret = kfifo_from_user(&test, buf, count, &copied); 96 97 mutex_unlock(&write_lock); 98 99 return ret ? ret : copied; 100 } 101 102 static ssize_t fifo_read(struct file *file, char __user *buf, 103 size_t count, loff_t *ppos) 104 { 105 int ret; 106 unsigned int copied; 107 108 if (mutex_lock_interruptible(&read_lock)) 109 return -ERESTARTSYS; 110 111 ret = kfifo_to_user(&test, buf, count, &copied); 112 113 mutex_unlock(&read_lock); 114 115 return ret ? ret : copied; 116 } 117 118 static const struct file_operations fifo_fops = { 119 .owner = THIS_MODULE, 120 .read = fifo_read, 121 .write = fifo_write, 122 }; 123 124 static int __init example_init(void) 125 { 126 #ifdef DYNAMIC 127 int ret; 128 129 ret = kfifo_alloc(&test, FIFO_SIZE, GFP_KERNEL); 130 if (ret) { 131 printk(KERN_ERR "error kfifo_alloc\n"); 132 return ret; 133 } 134 #endif 135 testfunc(); 136 137 if (proc_create(PROC_FIFO, 0, NULL, &fifo_fops) == NULL) { 138 #ifdef DYNAMIC 139 kfifo_free(&test); 140 #endif 141 return -ENOMEM; 142 } 143 return 0; 144 } 145 146 static void __exit example_exit(void) 147 { 148 remove_proc_entry(PROC_FIFO, NULL); 149 #ifdef DYNAMIC 150 kfifo_free(&test); 151 #endif 152 } 153 154 module_init(example_init); 155 module_exit(example_exit); 156 MODULE_LICENSE("GPL"); 157 MODULE_AUTHOR("Stefani Seibold <stefani@seibold.net>"); 158