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 int __init testfunc(void) 48 { 49 unsigned char buf[6]; 50 unsigned char i; 51 unsigned int ret; 52 53 printk(KERN_INFO "byte stream fifo test start\n"); 54 55 /* put string into the fifo */ 56 kfifo_in(&test, "hello", 5); 57 58 /* put values into the fifo */ 59 for (i = 0; i != 10; i++) 60 kfifo_put(&test, &i); 61 62 /* show the number of used elements */ 63 printk(KERN_INFO "fifo len: %u\n", kfifo_len(&test)); 64 65 /* get max of 5 bytes from the fifo */ 66 i = kfifo_out(&test, buf, 5); 67 printk(KERN_INFO "buf: %.*s\n", i, buf); 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 /* put values into the fifo until is full */ 77 for (i = 20; kfifo_put(&test, &i); i++) 78 ; 79 80 printk(KERN_INFO "queue len: %u\n", kfifo_len(&test)); 81 82 /* print out all values in the fifo */ 83 while (kfifo_get(&test, &i)) 84 printk("%d ", i); 85 printk("\n"); 86 87 return 0; 88 } 89 90 static ssize_t fifo_write(struct file *file, const char __user *buf, 91 size_t count, loff_t *ppos) 92 { 93 int ret; 94 unsigned int copied; 95 96 if (mutex_lock_interruptible(&write_lock)) 97 return -ERESTARTSYS; 98 99 ret = kfifo_from_user(&test, buf, count, &copied); 100 101 mutex_unlock(&write_lock); 102 103 return ret ? ret : copied; 104 } 105 106 static ssize_t fifo_read(struct file *file, char __user *buf, 107 size_t count, loff_t *ppos) 108 { 109 int ret; 110 unsigned int copied; 111 112 if (mutex_lock_interruptible(&read_lock)) 113 return -ERESTARTSYS; 114 115 ret = kfifo_to_user(&test, buf, count, &copied); 116 117 mutex_unlock(&read_lock); 118 119 return ret ? ret : copied; 120 } 121 122 static const struct file_operations fifo_fops = { 123 .owner = THIS_MODULE, 124 .read = fifo_read, 125 .write = fifo_write, 126 }; 127 128 static int __init example_init(void) 129 { 130 #ifdef DYNAMIC 131 int ret; 132 133 ret = kfifo_alloc(&test, FIFO_SIZE, GFP_KERNEL); 134 if (ret) { 135 printk(KERN_ERR "error kfifo_alloc\n"); 136 return ret; 137 } 138 #else 139 INIT_KFIFO(test); 140 #endif 141 testfunc(); 142 143 if (proc_create(PROC_FIFO, 0, NULL, &fifo_fops) == NULL) { 144 #ifdef DYNAMIC 145 kfifo_free(&test); 146 #endif 147 return -ENOMEM; 148 } 149 return 0; 150 } 151 152 static void __exit example_exit(void) 153 { 154 remove_proc_entry(PROC_FIFO, NULL); 155 #ifdef DYNAMIC 156 kfifo_free(&test); 157 #endif 158 } 159 160 module_init(example_init); 161 module_exit(example_exit); 162 MODULE_LICENSE("GPL"); 163 MODULE_AUTHOR("Stefani Seibold <stefani@seibold.net>"); 164