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1// SPDX-License-Identifier: GPL-2.0-only2/*3 * Sample kfifo int type implementation4 *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 3220 21/* name of the proc entry */22#define PROC_FIFO "int-fifo"23 24/* lock for procfs read access */25static DEFINE_MUTEX(read_access);26 27/* lock for procfs write access */28static 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 036#define DYNAMIC37#endif38 39#ifdef DYNAMIC40static DECLARE_KFIFO_PTR(test, int);41#else42static DEFINE_KFIFO(test, int, FIFO_SIZE);43#endif44 45static 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 52static 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 106static 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_access))113 return -ERESTARTSYS;114 115 ret = kfifo_from_user(&test, buf, count, &copied);116 117 mutex_unlock(&write_access);118 if (ret)119 return ret;120 121 return copied;122}123 124static ssize_t fifo_read(struct file *file, char __user *buf,125 size_t count, loff_t *ppos)126{127 int ret;128 unsigned int copied;129 130 if (mutex_lock_interruptible(&read_access))131 return -ERESTARTSYS;132 133 ret = kfifo_to_user(&test, buf, count, &copied);134 135 mutex_unlock(&read_access);136 if (ret)137 return ret;138 139 return copied;140}141 142static const struct proc_ops fifo_proc_ops = {143 .proc_read = fifo_read,144 .proc_write = fifo_write,145 .proc_lseek = noop_llseek,146};147 148static int __init example_init(void)149{150#ifdef DYNAMIC151 int ret;152 153 ret = kfifo_alloc(&test, FIFO_SIZE, GFP_KERNEL);154 if (ret) {155 printk(KERN_ERR "error kfifo_alloc\n");156 return ret;157 }158#endif159 if (testfunc() < 0) {160#ifdef DYNAMIC161 kfifo_free(&test);162#endif163 return -EIO;164 }165 166 if (proc_create(PROC_FIFO, 0, NULL, &fifo_proc_ops) == NULL) {167#ifdef DYNAMIC168 kfifo_free(&test);169#endif170 return -ENOMEM;171 }172 return 0;173}174 175static void __exit example_exit(void)176{177 remove_proc_entry(PROC_FIFO, NULL);178#ifdef DYNAMIC179 kfifo_free(&test);180#endif181}182 183module_init(example_init);184module_exit(example_exit);185MODULE_DESCRIPTION("Sample kfifo int type implementation");186MODULE_LICENSE("GPL");187MODULE_AUTHOR("Stefani Seibold <stefani@seibold.net>");188