1 /* 2 * Sample dynamic sized record fifo 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 variable sized record fifo. 18 */ 19 20 /* fifo size in elements (bytes) */ 21 #define FIFO_SIZE 128 22 23 /* name of the proc entry */ 24 #define PROC_FIFO "record-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 /* 42 * struct kfifo_rec_ptr_1 and STRUCT_KFIFO_REC_1 can handle records of a 43 * length between 0 and 255 bytes. 44 * 45 * struct kfifo_rec_ptr_2 and STRUCT_KFIFO_REC_2 can handle records of a 46 * length between 0 and 65535 bytes. 47 */ 48 49 #ifdef DYNAMIC 50 struct kfifo_rec_ptr_1 test; 51 52 #else 53 typedef STRUCT_KFIFO_REC_1(FIFO_SIZE) mytest; 54 55 static mytest test; 56 #endif 57 58 static int __init testfunc(void) 59 { 60 char buf[100]; 61 unsigned int i; 62 unsigned int ret; 63 struct { unsigned char buf[6]; } hello = { "hello" }; 64 65 printk(KERN_INFO "record fifo test start\n"); 66 67 kfifo_in(&test, &hello, sizeof(hello)); 68 69 /* show the size of the next record in the fifo */ 70 printk(KERN_INFO "fifo peek len: %u\n", kfifo_peek_len(&test)); 71 72 /* put in variable length data */ 73 for (i = 0; i < 10; i++) { 74 memset(buf, 'a' + i, i + 1); 75 kfifo_in(&test, buf, i + 1); 76 } 77 78 printk(KERN_INFO "fifo len: %u\n", kfifo_len(&test)); 79 80 /* show the first record without removing from the fifo */ 81 ret = kfifo_out_peek(&test, buf, sizeof(buf)); 82 if (ret) 83 printk(KERN_INFO "%.*s\n", ret, buf); 84 85 /* print out all records in the fifo */ 86 while (!kfifo_is_empty(&test)) { 87 ret = kfifo_out(&test, buf, sizeof(buf)); 88 printk(KERN_INFO "%.*s\n", ret, buf); 89 } 90 91 return 0; 92 } 93 94 static ssize_t fifo_write(struct file *file, const char __user *buf, 95 size_t count, loff_t *ppos) 96 { 97 int ret; 98 unsigned int copied; 99 100 if (mutex_lock_interruptible(&write_lock)) 101 return -ERESTARTSYS; 102 103 ret = kfifo_from_user(&test, buf, count, &copied); 104 105 mutex_unlock(&write_lock); 106 107 return ret ? ret : copied; 108 } 109 110 static ssize_t fifo_read(struct file *file, char __user *buf, 111 size_t count, loff_t *ppos) 112 { 113 int ret; 114 unsigned int copied; 115 116 if (mutex_lock_interruptible(&read_lock)) 117 return -ERESTARTSYS; 118 119 ret = kfifo_to_user(&test, buf, count, &copied); 120 121 mutex_unlock(&read_lock); 122 123 return ret ? ret : copied; 124 } 125 126 static const struct file_operations fifo_fops = { 127 .owner = THIS_MODULE, 128 .read = fifo_read, 129 .write = fifo_write, 130 }; 131 132 static int __init example_init(void) 133 { 134 #ifdef DYNAMIC 135 int ret; 136 137 ret = kfifo_alloc(&test, FIFO_SIZE, GFP_KERNEL); 138 if (ret) { 139 printk(KERN_ERR "error kfifo_alloc\n"); 140 return ret; 141 } 142 #else 143 INIT_KFIFO(test); 144 #endif 145 testfunc(); 146 147 if (proc_create(PROC_FIFO, 0, NULL, &fifo_fops) == NULL) { 148 #ifdef DYNAMIC 149 kfifo_free(&test); 150 #endif 151 return -ENOMEM; 152 } 153 return 0; 154 } 155 156 static void __exit example_exit(void) 157 { 158 remove_proc_entry(PROC_FIFO, NULL); 159 #ifdef DYNAMIC 160 kfifo_free(&test); 161 #endif 162 } 163 164 module_init(example_init); 165 module_exit(example_exit); 166 MODULE_LICENSE("GPL"); 167 MODULE_AUTHOR("Stefani Seibold <stefani@seibold.net>"); 168