1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Sample kfifo int type implementation 4 * 5 * Copyright (C) 2010 Stefani Seibold <stefani@seibold.net> 6 */ 7 8 #include <linux/init.h> 9 #include <linux/module.h> 10 #include <linux/proc_fs.h> 11 #include <linux/mutex.h> 12 #include <linux/kfifo.h> 13 14 /* 15 * This module shows how to create a int type fifo. 16 */ 17 18 /* fifo size in elements (ints) */ 19 #define FIFO_SIZE 32 20 21 /* name of the proc entry */ 22 #define PROC_FIFO "int-fifo" 23 24 /* lock for procfs read access */ 25 static DEFINE_MUTEX(read_lock); 26 27 /* lock for procfs write access */ 28 static DEFINE_MUTEX(write_lock); 29 30 /* 31 * define DYNAMIC in this example for a dynamically allocated fifo. 32 * 33 * Otherwise the fifo storage will be a part of the fifo structure. 34 */ 35 #if 0 36 #define DYNAMIC 37 #endif 38 39 #ifdef DYNAMIC 40 static DECLARE_KFIFO_PTR(test, int); 41 #else 42 static DEFINE_KFIFO(test, int, FIFO_SIZE); 43 #endif 44 45 static const int expected_result[FIFO_SIZE] = { 46 3, 4, 5, 6, 7, 8, 9, 0, 47 1, 20, 21, 22, 23, 24, 25, 26, 48 27, 28, 29, 30, 31, 32, 33, 34, 49 35, 36, 37, 38, 39, 40, 41, 42, 50 }; 51 52 static int __init testfunc(void) 53 { 54 int buf[6]; 55 int i, j; 56 unsigned int ret; 57 58 printk(KERN_INFO "int fifo test start\n"); 59 60 /* put values into the fifo */ 61 for (i = 0; i != 10; i++) 62 kfifo_put(&test, i); 63 64 /* show the number of used elements */ 65 printk(KERN_INFO "fifo len: %u\n", kfifo_len(&test)); 66 67 /* get max of 2 elements from the fifo */ 68 ret = kfifo_out(&test, buf, 2); 69 printk(KERN_INFO "ret: %d\n", ret); 70 /* and put it back to the end of the fifo */ 71 ret = kfifo_in(&test, buf, ret); 72 printk(KERN_INFO "ret: %d\n", ret); 73 74 /* skip first element of the fifo */ 75 printk(KERN_INFO "skip 1st element\n"); 76 kfifo_skip(&test); 77 78 /* put values into the fifo until is full */ 79 for (i = 20; kfifo_put(&test, i); i++) 80 ; 81 82 printk(KERN_INFO "queue len: %u\n", kfifo_len(&test)); 83 84 /* show the first value without removing from the fifo */ 85 if (kfifo_peek(&test, &i)) 86 printk(KERN_INFO "%d\n", i); 87 88 /* check the correctness of all values in the fifo */ 89 j = 0; 90 while (kfifo_get(&test, &i)) { 91 printk(KERN_INFO "item = %d\n", i); 92 if (i != expected_result[j++]) { 93 printk(KERN_WARNING "value mismatch: test failed\n"); 94 return -EIO; 95 } 96 } 97 if (j != ARRAY_SIZE(expected_result)) { 98 printk(KERN_WARNING "size mismatch: test failed\n"); 99 return -EIO; 100 } 101 printk(KERN_INFO "test passed\n"); 102 103 return 0; 104 } 105 106 static ssize_t fifo_write(struct file *file, const char __user *buf, 107 size_t count, loff_t *ppos) 108 { 109 int ret; 110 unsigned int copied; 111 112 if (mutex_lock_interruptible(&write_lock)) 113 return -ERESTARTSYS; 114 115 ret = kfifo_from_user(&test, buf, count, &copied); 116 117 mutex_unlock(&write_lock); 118 119 return ret ? ret : copied; 120 } 121 122 static ssize_t fifo_read(struct file *file, char __user *buf, 123 size_t count, loff_t *ppos) 124 { 125 int ret; 126 unsigned int copied; 127 128 if (mutex_lock_interruptible(&read_lock)) 129 return -ERESTARTSYS; 130 131 ret = kfifo_to_user(&test, buf, count, &copied); 132 133 mutex_unlock(&read_lock); 134 135 return ret ? ret : copied; 136 } 137 138 static const struct file_operations fifo_fops = { 139 .owner = THIS_MODULE, 140 .read = fifo_read, 141 .write = fifo_write, 142 .llseek = noop_llseek, 143 }; 144 145 static int __init example_init(void) 146 { 147 #ifdef DYNAMIC 148 int ret; 149 150 ret = kfifo_alloc(&test, FIFO_SIZE, GFP_KERNEL); 151 if (ret) { 152 printk(KERN_ERR "error kfifo_alloc\n"); 153 return ret; 154 } 155 #endif 156 if (testfunc() < 0) { 157 #ifdef DYNAMIC 158 kfifo_free(&test); 159 #endif 160 return -EIO; 161 } 162 163 if (proc_create(PROC_FIFO, 0, NULL, &fifo_fops) == NULL) { 164 #ifdef DYNAMIC 165 kfifo_free(&test); 166 #endif 167 return -ENOMEM; 168 } 169 return 0; 170 } 171 172 static void __exit example_exit(void) 173 { 174 remove_proc_entry(PROC_FIFO, NULL); 175 #ifdef DYNAMIC 176 kfifo_free(&test); 177 #endif 178 } 179 180 module_init(example_init); 181 module_exit(example_exit); 182 MODULE_LICENSE("GPL"); 183 MODULE_AUTHOR("Stefani Seibold <stefani@seibold.net>"); 184