1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Sample dynamic sized record fifo 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 variable sized record fifo. 16 */ 17 18 /* fifo size in elements (bytes) */ 19 #define FIFO_SIZE 128 20 21 /* name of the proc entry */ 22 #define PROC_FIFO "record-fifo" 23 24 /* lock for procfs read access */ 25 static DEFINE_MUTEX(read_access); 26 27 /* lock for procfs write access */ 28 static DEFINE_MUTEX(write_access); 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 /* 40 * struct kfifo_rec_ptr_1 and STRUCT_KFIFO_REC_1 can handle records of a 41 * length between 0 and 255 bytes. 42 * 43 * struct kfifo_rec_ptr_2 and STRUCT_KFIFO_REC_2 can handle records of a 44 * length between 0 and 65535 bytes. 45 */ 46 47 #ifdef DYNAMIC 48 struct kfifo_rec_ptr_1 test; 49 50 #else 51 typedef STRUCT_KFIFO_REC_1(FIFO_SIZE) mytest; 52 53 static mytest test; 54 #endif 55 56 static const char *expected_result[] = { 57 "a", 58 "bb", 59 "ccc", 60 "dddd", 61 "eeeee", 62 "ffffff", 63 "ggggggg", 64 "hhhhhhhh", 65 "iiiiiiiii", 66 "jjjjjjjjjj", 67 }; 68 69 static int __init testfunc(void) 70 { 71 char buf[100]; 72 unsigned int i; 73 unsigned int ret; 74 struct { unsigned char buf[6]; } hello = { "hello" }; 75 76 printk(KERN_INFO "record fifo test start\n"); 77 78 kfifo_in(&test, &hello, sizeof(hello)); 79 80 /* show the size of the next record in the fifo */ 81 printk(KERN_INFO "fifo peek len: %u\n", kfifo_peek_len(&test)); 82 83 /* put in variable length data */ 84 for (i = 0; i < 10; i++) { 85 memset(buf, 'a' + i, i + 1); 86 kfifo_in(&test, buf, i + 1); 87 } 88 89 /* skip first element of the fifo */ 90 printk(KERN_INFO "skip 1st element\n"); 91 kfifo_skip(&test); 92 93 printk(KERN_INFO "fifo len: %u\n", kfifo_len(&test)); 94 95 /* show the first record without removing from the fifo */ 96 ret = kfifo_out_peek(&test, buf, sizeof(buf)); 97 if (ret) 98 printk(KERN_INFO "%.*s\n", ret, buf); 99 100 /* check the correctness of all values in the fifo */ 101 i = 0; 102 while (!kfifo_is_empty(&test)) { 103 ret = kfifo_out(&test, buf, sizeof(buf)); 104 buf[ret] = '\0'; 105 printk(KERN_INFO "item = %.*s\n", ret, buf); 106 if (strcmp(buf, expected_result[i++])) { 107 printk(KERN_WARNING "value mismatch: test failed\n"); 108 return -EIO; 109 } 110 } 111 if (i != ARRAY_SIZE(expected_result)) { 112 printk(KERN_WARNING "size mismatch: test failed\n"); 113 return -EIO; 114 } 115 printk(KERN_INFO "test passed\n"); 116 117 return 0; 118 } 119 120 static ssize_t fifo_write(struct file *file, const char __user *buf, 121 size_t count, loff_t *ppos) 122 { 123 int ret; 124 unsigned int copied; 125 126 if (mutex_lock_interruptible(&write_access)) 127 return -ERESTARTSYS; 128 129 ret = kfifo_from_user(&test, buf, count, &copied); 130 131 mutex_unlock(&write_access); 132 if (ret) 133 return ret; 134 135 return copied; 136 } 137 138 static ssize_t fifo_read(struct file *file, char __user *buf, 139 size_t count, loff_t *ppos) 140 { 141 int ret; 142 unsigned int copied; 143 144 if (mutex_lock_interruptible(&read_access)) 145 return -ERESTARTSYS; 146 147 ret = kfifo_to_user(&test, buf, count, &copied); 148 149 mutex_unlock(&read_access); 150 if (ret) 151 return ret; 152 153 return copied; 154 } 155 156 static const struct proc_ops fifo_proc_ops = { 157 .proc_read = fifo_read, 158 .proc_write = fifo_write, 159 .proc_lseek = noop_llseek, 160 }; 161 162 static int __init example_init(void) 163 { 164 #ifdef DYNAMIC 165 int ret; 166 167 ret = kfifo_alloc(&test, FIFO_SIZE, GFP_KERNEL); 168 if (ret) { 169 printk(KERN_ERR "error kfifo_alloc\n"); 170 return ret; 171 } 172 #else 173 INIT_KFIFO(test); 174 #endif 175 if (testfunc() < 0) { 176 #ifdef DYNAMIC 177 kfifo_free(&test); 178 #endif 179 return -EIO; 180 } 181 182 if (proc_create(PROC_FIFO, 0, NULL, &fifo_proc_ops) == NULL) { 183 #ifdef DYNAMIC 184 kfifo_free(&test); 185 #endif 186 return -ENOMEM; 187 } 188 return 0; 189 } 190 191 static void __exit example_exit(void) 192 { 193 remove_proc_entry(PROC_FIFO, NULL); 194 #ifdef DYNAMIC 195 kfifo_free(&test); 196 #endif 197 } 198 199 module_init(example_init); 200 module_exit(example_exit); 201 MODULE_LICENSE("GPL"); 202 MODULE_AUTHOR("Stefani Seibold <stefani@seibold.net>"); 203