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202 lines
4.0 KiB
202 lines
4.0 KiB
// SPDX-License-Identifier: GPL-2.0-only |
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/* |
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* Sample dynamic sized record fifo implementation |
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* |
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* Copyright (C) 2010 Stefani Seibold <[email protected]> |
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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 variable sized record fifo. |
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*/ |
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/* fifo size in elements (bytes) */ |
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#define FIFO_SIZE 128 |
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/* name of the proc entry */ |
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#define PROC_FIFO "record-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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/* |
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* struct kfifo_rec_ptr_1 and STRUCT_KFIFO_REC_1 can handle records of a |
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* length between 0 and 255 bytes. |
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* |
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* struct kfifo_rec_ptr_2 and STRUCT_KFIFO_REC_2 can handle records of a |
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* length between 0 and 65535 bytes. |
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*/ |
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#ifdef DYNAMIC |
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struct kfifo_rec_ptr_1 test; |
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#else |
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typedef STRUCT_KFIFO_REC_1(FIFO_SIZE) mytest; |
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static mytest test; |
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#endif |
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static const char *expected_result[] = { |
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"a", |
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"bb", |
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"ccc", |
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"dddd", |
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"eeeee", |
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"ffffff", |
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"ggggggg", |
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"hhhhhhhh", |
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"iiiiiiiii", |
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"jjjjjjjjjj", |
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}; |
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static int __init testfunc(void) |
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{ |
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char buf[100]; |
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unsigned int i; |
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unsigned int ret; |
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struct { unsigned char buf[6]; } hello = { "hello" }; |
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printk(KERN_INFO "record fifo test start\n"); |
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kfifo_in(&test, &hello, sizeof(hello)); |
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/* show the size of the next record in the fifo */ |
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printk(KERN_INFO "fifo peek len: %u\n", kfifo_peek_len(&test)); |
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/* put in variable length data */ |
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for (i = 0; i < 10; i++) { |
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memset(buf, 'a' + i, i + 1); |
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kfifo_in(&test, buf, i + 1); |
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} |
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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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printk(KERN_INFO "fifo len: %u\n", kfifo_len(&test)); |
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/* show the first record without removing from the fifo */ |
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ret = kfifo_out_peek(&test, buf, sizeof(buf)); |
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if (ret) |
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printk(KERN_INFO "%.*s\n", ret, buf); |
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/* check the correctness of all values in the fifo */ |
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i = 0; |
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while (!kfifo_is_empty(&test)) { |
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ret = kfifo_out(&test, buf, sizeof(buf)); |
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buf[ret] = '\0'; |
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printk(KERN_INFO "item = %.*s\n", ret, buf); |
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if (strcmp(buf, expected_result[i++])) { |
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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 (i != 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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if (ret) |
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return ret; |
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return 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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if (ret) |
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return ret; |
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return 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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#else |
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INIT_KFIFO(test); |
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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 <[email protected]>");
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