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// SPDX-License-Identifier: GPL-2.0-only
/*
* Sample dynamic sized record fifo implementation
*
* Copyright (C) 2010 Stefani Seibold <stefani@seibold.net>
*/
#include <linux/init.h>
#include <linux/module.h>
#include <linux/proc_fs.h>
#include <linux/mutex.h>
#include <linux/kfifo.h>
/*
* This module shows how to create a variable sized record fifo.
*/
/* fifo size in elements (bytes) */
#define FIFO_SIZE 128
/* name of the proc entry */
#define PROC_FIFO "record-fifo"
/* lock for procfs read access */
static DEFINE_MUTEX(read_lock);
/* lock for procfs write access */
static DEFINE_MUTEX(write_lock);
/*
* define DYNAMIC in this example for a dynamically allocated fifo.
*
* Otherwise the fifo storage will be a part of the fifo structure.
*/
#if 0
#define DYNAMIC
#endif
/*
* struct kfifo_rec_ptr_1 and STRUCT_KFIFO_REC_1 can handle records of a
* length between 0 and 255 bytes.
*
* struct kfifo_rec_ptr_2 and STRUCT_KFIFO_REC_2 can handle records of a
* length between 0 and 65535 bytes.
*/
#ifdef DYNAMIC
struct kfifo_rec_ptr_1 test;
#else
typedef STRUCT_KFIFO_REC_1(FIFO_SIZE) mytest;
static mytest test;
#endif
static const char *expected_result[] = {
"a",
"bb",
"ccc",
"dddd",
"eeeee",
"ffffff",
"ggggggg",
"hhhhhhhh",
"iiiiiiiii",
"jjjjjjjjjj",
};
static int __init testfunc(void)
{
char buf[100];
unsigned int i;
unsigned int ret;
struct { unsigned char buf[6]; } hello = { "hello" };
printk(KERN_INFO "record fifo test start\n");
kfifo_in(&test, &hello, sizeof(hello));
/* show the size of the next record in the fifo */
printk(KERN_INFO "fifo peek len: %u\n", kfifo_peek_len(&test));
/* put in variable length data */
for (i = 0; i < 10; i++) {
memset(buf, 'a' + i, i + 1);
kfifo_in(&test, buf, i + 1);
}
/* skip first element of the fifo */
printk(KERN_INFO "skip 1st element\n");
kfifo_skip(&test);
printk(KERN_INFO "fifo len: %u\n", kfifo_len(&test));
/* show the first record without removing from the fifo */
ret = kfifo_out_peek(&test, buf, sizeof(buf));
if (ret)
printk(KERN_INFO "%.*s\n", ret, buf);
/* check the correctness of all values in the fifo */
i = 0;
while (!kfifo_is_empty(&test)) {
ret = kfifo_out(&test, buf, sizeof(buf));
buf[ret] = '\0';
printk(KERN_INFO "item = %.*s\n", ret, buf);
if (strcmp(buf, expected_result[i++])) {
printk(KERN_WARNING "value mismatch: test failed\n");
return -EIO;
}
}
if (i != ARRAY_SIZE(expected_result)) {
printk(KERN_WARNING "size mismatch: test failed\n");
return -EIO;
}
printk(KERN_INFO "test passed\n");
return 0;
}
static ssize_t fifo_write(struct file *file, const char __user *buf,
size_t count, loff_t *ppos)
{
int ret;
unsigned int copied;
if (mutex_lock_interruptible(&write_lock))
return -ERESTARTSYS;
ret = kfifo_from_user(&test, buf, count, &copied);
mutex_unlock(&write_lock);
return ret ? ret : copied;
}
static ssize_t fifo_read(struct file *file, char __user *buf,
size_t count, loff_t *ppos)
{
int ret;
unsigned int copied;
if (mutex_lock_interruptible(&read_lock))
return -ERESTARTSYS;
ret = kfifo_to_user(&test, buf, count, &copied);
mutex_unlock(&read_lock);
return ret ? ret : copied;
}
static const struct file_operations fifo_fops = {
.owner = THIS_MODULE,
.read = fifo_read,
.write = fifo_write,
.llseek = noop_llseek,
};
static int __init example_init(void)
{
#ifdef DYNAMIC
int ret;
ret = kfifo_alloc(&test, FIFO_SIZE, GFP_KERNEL);
if (ret) {
printk(KERN_ERR "error kfifo_alloc\n");
return ret;
}
#else
INIT_KFIFO(test);
#endif
if (testfunc() < 0) {
#ifdef DYNAMIC
kfifo_free(&test);
#endif
return -EIO;
}
if (proc_create(PROC_FIFO, 0, NULL, &fifo_fops) == NULL) {
#ifdef DYNAMIC
kfifo_free(&test);
#endif
return -ENOMEM;
}
return 0;
}
static void __exit example_exit(void)
{
remove_proc_entry(PROC_FIFO, NULL);
#ifdef DYNAMIC
kfifo_free(&test);
#endif
}
module_init(example_init);
module_exit(example_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Stefani Seibold <stefani@seibold.net>");
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