168 lines
3.3 KiB
C
168 lines
3.3 KiB
C
/*
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* Sample dynamic sized record fifo 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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* Released under the GPL version 2 only.
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*
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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 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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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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/* print out all records in the fifo */
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while (!kfifo_is_empty(&test)) {
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ret = kfifo_out(&test, buf, sizeof(buf));
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printk(KERN_INFO "%.*s\n", ret, buf);
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}
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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 file_operations fifo_fops = {
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.owner = THIS_MODULE,
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.read = fifo_read,
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.write = fifo_write,
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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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testfunc();
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if (proc_create(PROC_FIFO, 0, NULL, &fifo_fops) == 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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