183 lines
3.7 KiB
C
183 lines
3.7 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Sample kfifo int type implementation
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*
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* Copyright (C) 2010 Stefani Seibold <stefani@seibold.net>
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*/
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#include <linux/init.h>
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#include <linux/module.h>
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#include <linux/proc_fs.h>
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#include <linux/mutex.h>
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#include <linux/kfifo.h>
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/*
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* This module shows how to create a int type fifo.
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*/
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/* fifo size in elements (ints) */
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#define FIFO_SIZE 32
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/* name of the proc entry */
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#define PROC_FIFO "int-fifo"
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/* lock for procfs read access */
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static DEFINE_MUTEX(read_lock);
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/* lock for procfs write access */
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static DEFINE_MUTEX(write_lock);
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/*
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* define DYNAMIC in this example for a dynamically allocated fifo.
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*
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* Otherwise the fifo storage will be a part of the fifo structure.
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*/
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#if 0
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#define DYNAMIC
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#endif
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#ifdef DYNAMIC
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static DECLARE_KFIFO_PTR(test, int);
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#else
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static DEFINE_KFIFO(test, int, FIFO_SIZE);
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#endif
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static const int expected_result[FIFO_SIZE] = {
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3, 4, 5, 6, 7, 8, 9, 0,
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1, 20, 21, 22, 23, 24, 25, 26,
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27, 28, 29, 30, 31, 32, 33, 34,
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35, 36, 37, 38, 39, 40, 41, 42,
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};
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static int __init testfunc(void)
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{
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int buf[6];
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int i, j;
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unsigned int ret;
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printk(KERN_INFO "int fifo test start\n");
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/* put values into the fifo */
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for (i = 0; i != 10; i++)
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kfifo_put(&test, i);
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/* show the number of used elements */
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printk(KERN_INFO "fifo len: %u\n", kfifo_len(&test));
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/* get max of 2 elements from the fifo */
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ret = kfifo_out(&test, buf, 2);
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printk(KERN_INFO "ret: %d\n", ret);
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/* and put it back to the end of the fifo */
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ret = kfifo_in(&test, buf, ret);
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printk(KERN_INFO "ret: %d\n", ret);
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/* skip first element of the fifo */
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printk(KERN_INFO "skip 1st element\n");
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kfifo_skip(&test);
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/* put values into the fifo until is full */
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for (i = 20; kfifo_put(&test, i); i++)
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;
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printk(KERN_INFO "queue len: %u\n", kfifo_len(&test));
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/* show the first value without removing from the fifo */
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if (kfifo_peek(&test, &i))
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printk(KERN_INFO "%d\n", i);
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/* check the correctness of all values in the fifo */
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j = 0;
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while (kfifo_get(&test, &i)) {
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printk(KERN_INFO "item = %d\n", i);
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if (i != expected_result[j++]) {
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printk(KERN_WARNING "value mismatch: test failed\n");
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return -EIO;
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}
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}
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if (j != ARRAY_SIZE(expected_result)) {
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printk(KERN_WARNING "size mismatch: test failed\n");
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return -EIO;
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}
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printk(KERN_INFO "test passed\n");
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return 0;
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}
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static ssize_t fifo_write(struct file *file, const char __user *buf,
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size_t count, loff_t *ppos)
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{
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int ret;
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unsigned int copied;
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if (mutex_lock_interruptible(&write_lock))
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return -ERESTARTSYS;
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ret = kfifo_from_user(&test, buf, count, &copied);
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mutex_unlock(&write_lock);
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return ret ? ret : copied;
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}
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static ssize_t fifo_read(struct file *file, char __user *buf,
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size_t count, loff_t *ppos)
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{
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int ret;
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unsigned int copied;
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if (mutex_lock_interruptible(&read_lock))
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return -ERESTARTSYS;
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ret = kfifo_to_user(&test, buf, count, &copied);
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mutex_unlock(&read_lock);
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return ret ? ret : copied;
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}
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static const struct proc_ops fifo_proc_ops = {
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.proc_read = fifo_read,
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.proc_write = fifo_write,
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.proc_lseek = noop_llseek,
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};
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static int __init example_init(void)
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{
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#ifdef DYNAMIC
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int ret;
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ret = kfifo_alloc(&test, FIFO_SIZE, GFP_KERNEL);
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if (ret) {
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printk(KERN_ERR "error kfifo_alloc\n");
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return ret;
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}
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#endif
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if (testfunc() < 0) {
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#ifdef DYNAMIC
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kfifo_free(&test);
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#endif
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return -EIO;
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}
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if (proc_create(PROC_FIFO, 0, NULL, &fifo_proc_ops) == NULL) {
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#ifdef DYNAMIC
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kfifo_free(&test);
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#endif
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return -ENOMEM;
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}
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return 0;
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}
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static void __exit example_exit(void)
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{
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remove_proc_entry(PROC_FIFO, NULL);
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#ifdef DYNAMIC
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kfifo_free(&test);
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#endif
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}
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module_init(example_init);
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module_exit(example_exit);
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Stefani Seibold <stefani@seibold.net>");
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