/*
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* Copyright (C) 2024 LingYun IoT System Studio
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* Author: Guo Wenxue <guowenxue@gmail.com>
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*
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* A character skeleton driver example in linux kernel.
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*/
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#include <linux/module.h>
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#include <linux/init.h>
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#include <linux/kernel.h> /* printk() */
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#include <linux/fs.h> /* everything... */
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#include <linux/errno.h> /* error codes */
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#include <linux/types.h> /* size_t */
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#include <linux/cdev.h> /* cdev */
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#include <linux/version.h> /* kernel version code */
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#include <linux/moduleparam.h>
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//#define CONFIG_DYNAMIC_ALLOC
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/* device name and major number */
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#define DEV_NAME "chrdev"
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#ifdef CONFIG_DYNAMIC_ALLOC
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#define DEV_MAJOR 0
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#else
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#define DEV_MAJOR 79
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#endif
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int dev_major = DEV_MAJOR;
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module_param(dev_major, int, S_IRUGO);
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#ifdef CONFIG_DYNAMIC_ALLOC
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struct cdev *cdev;
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#else
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struct cdev cdev;
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#endif
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static int chrdev_open (struct inode *inode, struct file *file)
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{
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return 0;
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}
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static int chrdev_close (struct inode *node, struct file *file)
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{
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return 0;
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}
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static struct file_operations chrdev_fops = {
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.owner = THIS_MODULE,
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.open = chrdev_open, /* open() implementation */
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.release = chrdev_close, /* close() implementation */
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};
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static int __init chrdev_init(void)
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{
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dev_t devno;
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int rv;
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/* 1. Allocate device number */
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if(0 != dev_major)
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{
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devno = MKDEV(dev_major, 0);
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rv = register_chrdev_region(devno, 1, DEV_NAME);
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}
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else
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{
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rv = alloc_chrdev_region(&devno, 0, 1, DEV_NAME);
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dev_major = MAJOR(devno);
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}
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if(rv < 0)
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{
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printk(KERN_ERR "%s driver can't use major %d\n", DEV_NAME, dev_major);
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return -ENODEV;
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}
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/* 2. Allocate and initialize cdev */
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#ifdef CONFIG_DYNAMIC_ALLOC
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cdev = cdev_alloc();
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if( !cdev )
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{
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printk(KERN_ERR "Unable to allocate cdev\n");
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goto failed1;
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}
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cdev_init(cdev, &chrdev_fops);
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#else
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cdev_init(&cdev, &chrdev_fops);
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cdev.owner = THIS_MODULE;
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#endif
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/* 3. Register cdev to linux kernel */
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#ifdef CONFIG_DYNAMIC_ALLOC
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rv = cdev_add(cdev, devno, 1);
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#else
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rv = cdev_add(&cdev, devno, 1);
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#endif
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if( rv )
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{
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rv = -ENODEV;
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printk(KERN_ERR "%s driver regist failed, rv=%d\n", DEV_NAME, rv);
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goto failed1;
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}
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printk(KERN_INFO "%s driver on major[%d] installed.\n", DEV_NAME, dev_major);
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return 0;
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failed1:
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unregister_chrdev_region(devno, 1);
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printk(KERN_ERR "%s driver installed failed.\n", DEV_NAME);
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return rv;
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}
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static void __exit chrdev_exit(void)
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{
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#ifdef CONFIG_DYNAMIC_ALLOC
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cdev_del(cdev);
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#else
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cdev_del(&cdev);
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#endif
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unregister_chrdev_region(MKDEV(dev_major,0), 1);
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printk(KERN_INFO "%s driver removed!\n", DEV_NAME);
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return;
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}
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module_init(chrdev_init);
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module_exit(chrdev_exit);
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MODULE_LICENSE("Dual BSD/GPL");
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MODULE_AUTHOR("GuoWenxue <guowenxue@gmail.com>");
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