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1// SPDX-License-Identifier: GPL-2.0-only2/*3 * Sample dynamic sized record fifo 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 variable sized record fifo.16 */17 18/* fifo size in elements (bytes) */19#define FIFO_SIZE 12820 21/* name of the proc entry */22#define PROC_FIFO "record-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/*40 * struct kfifo_rec_ptr_1 and STRUCT_KFIFO_REC_1 can handle records of a41 * length between 0 and 255 bytes.42 *43 * struct kfifo_rec_ptr_2 and STRUCT_KFIFO_REC_2 can handle records of a44 * length between 0 and 65535 bytes.45 */46 47#ifdef DYNAMIC48struct kfifo_rec_ptr_1 test;49 50#else51typedef STRUCT_KFIFO_REC_1(FIFO_SIZE) mytest;52 53static mytest test;54#endif55 56static 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 69static 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 120static 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 138static 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 156static const struct proc_ops fifo_proc_ops = {157 .proc_read = fifo_read,158 .proc_write = fifo_write,159 .proc_lseek = noop_llseek,160};161 162static int __init example_init(void)163{164#ifdef DYNAMIC165 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#else173 INIT_KFIFO(test);174#endif175 if (testfunc() < 0) {176#ifdef DYNAMIC177 kfifo_free(&test);178#endif179 return -EIO;180 }181 182 if (proc_create(PROC_FIFO, 0, NULL, &fifo_proc_ops) == NULL) {183#ifdef DYNAMIC184 kfifo_free(&test);185#endif186 return -ENOMEM;187 }188 return 0;189}190 191static void __exit example_exit(void)192{193 remove_proc_entry(PROC_FIFO, NULL);194#ifdef DYNAMIC195 kfifo_free(&test);196#endif197}198 199module_init(example_init);200module_exit(example_exit);201MODULE_DESCRIPTION("Sample dynamic sized record fifo implementation");202MODULE_LICENSE("GPL");203MODULE_AUTHOR("Stefani Seibold <stefani@seibold.net>");204