samples/kfifo/record-example.c

   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 const char *expected_result[] = {
  59         "a",
  60         "bb",
  61         "ccc",
  62         "dddd",
  63         "eeeee",
  64         "ffffff",
  65         "ggggggg",
  66         "hhhhhhhh",
  67         "iiiiiiiii",
  68         "jjjjjjjjjj",
  69 };
  70
  71 static int __init testfunc(void)
  72 {
  73         char            buf[100];
  74         unsigned int    i;
  75         unsigned int    ret;
  76         struct { unsigned char buf[6]; } hello = { "hello" };
  77
  78         printk(KERN_INFO "record fifo test start\n");
  79
  80         kfifo_in(&test, &hello, sizeof(hello));
  81
  82         /* show the size of the next record in the fifo */
  83         printk(KERN_INFO "fifo peek len: %u\n", kfifo_peek_len(&test));
  84
  85         /* put in variable length data */
  86         for (i = 0; i < 10; i++) {
  87                 memset(buf, 'a' + i, i + 1);
  88                 kfifo_in(&test, buf, i + 1);
  89         }
  90
  91         /* skip first element of the fifo */
  92         printk(KERN_INFO "skip 1st element\n");
  93         kfifo_skip(&test);
  94
  95         printk(KERN_INFO "fifo len: %u\n", kfifo_len(&test));
  96
  97         /* show the first record without removing from the fifo */
  98         ret = kfifo_out_peek(&test, buf, sizeof(buf));
  99         if (ret)
 100                 printk(KERN_INFO "%.*s\n", ret, buf);
 101
 102         /* check the correctness of all values in the fifo */
 103         i = 0;
 104         while (!kfifo_is_empty(&test)) {
 105                 ret = kfifo_out(&test, buf, sizeof(buf));
 106                 buf[ret] = '\0';
 107                 printk(KERN_INFO "item = %.*s\n", ret, buf);
 108                 if (strcmp(buf, expected_result[i++])) {
 109                         printk(KERN_WARNING "value mismatch: test failed\n");
 110                         return -EIO;
 111                 }
 112         }
 113         if (i != ARRAY_SIZE(expected_result)) {
 114                 printk(KERN_WARNING "size mismatch: test failed\n");
 115                 return -EIO;
 116         }
 117         printk(KERN_INFO "test passed\n");
 118
 119         return 0;
 120 }
 121
 122 static ssize_t fifo_write(struct file *file, const char __user *buf,
 123                                                 size_t count, loff_t *ppos)
 124 {
 125         int ret;
 126         unsigned int copied;
 127
 128         if (mutex_lock_interruptible(&write_lock))
 129                 return -ERESTARTSYS;
 130
 131         ret = kfifo_from_user(&test, buf, count, &copied);
 132
 133         mutex_unlock(&write_lock);
 134
 135         return ret ? ret : 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_lock))
 145                 return -ERESTARTSYS;
 146
 147         ret = kfifo_to_user(&test, buf, count, &copied);
 148
 149         mutex_unlock(&read_lock);
 150
 151         return ret ? ret : copied;
 152 }
 153
 154 static const struct file_operations fifo_fops = {
 155         .owner          = THIS_MODULE,
 156         .read           = fifo_read,
 157         .write          = fifo_write,
 158         .llseek         = noop_llseek,
 159 };
 160
 161 static int __init example_init(void)
 162 {
 163 #ifdef DYNAMIC
 164         int ret;
 165
 166         ret = kfifo_alloc(&test, FIFO_SIZE, GFP_KERNEL);
 167         if (ret) {
 168                 printk(KERN_ERR "error kfifo_alloc\n");
 169                 return ret;
 170         }
 171 #else
 172         INIT_KFIFO(test);
 173 #endif
 174         if (testfunc() < 0) {
 175 #ifdef DYNAMIC
 176                 kfifo_free(&test);
 177 #endif
 178                 return -EIO;
 179         }
 180
 181         if (proc_create(PROC_FIFO, 0, NULL, &fifo_fops) == NULL) {
 182 #ifdef DYNAMIC
 183                 kfifo_free(&test);
 184 #endif
 185                 return -ENOMEM;
 186         }
 187         return 0;
 188 }
 189
 190 static void __exit example_exit(void)
 191 {
 192         remove_proc_entry(PROC_FIFO, NULL);
 193 #ifdef DYNAMIC
 194         kfifo_free(&test);
 195 #endif
 196 }
 197
 198 module_init(example_init);
 199 module_exit(example_exit);
 200 MODULE_LICENSE("GPL");
 201 MODULE_AUTHOR("Stefani Seibold <stefani@seibold.net>");