| commit | author | age | ||
| b8e5f6 | 1 | /* |
| G | 2 | * Copyright (C) 2024 LingYun IoT System Studio |
| 3 | * Author: Guo Wenxue <guowenxue@gmail.com> | |
| 4 | * | |
| 5 | * A character skeleton driver example in linux kernel. | |
| 6 | */ | |
| 7 | ||
| 8 | #include <linux/module.h> | |
| 9 | #include <linux/init.h> | |
| 10 | #include <linux/kernel.h> /* printk() */ | |
| 11 | #include <linux/fs.h> /* everything... */ | |
| 12 | #include <linux/errno.h> /* error codes */ | |
| 13 | #include <linux/types.h> /* size_t */ | |
| 14 | #include <linux/cdev.h> /* cdev */ | |
| 15 | #include <linux/version.h> /* kernel version code */ | |
| 16 | #include <linux/moduleparam.h> | |
| 17 | ||
| 18 | //#define CONFIG_DYNAMIC_ALLOC | |
| 19 | ||
| 20 | /* device name and major number */ | |
| 21 | #define DEV_NAME "chrdev" | |
| 22 | ||
| 23 | #ifdef CONFIG_DYNAMIC_ALLOC | |
| 24 | #define DEV_MAJOR 0 | |
| 25 | #else | |
| 26 | #define DEV_MAJOR 79 | |
| 27 | #endif | |
| 28 | ||
| 29 | int dev_major = DEV_MAJOR; | |
| 30 | module_param(dev_major, int, S_IRUGO); | |
| 31 | ||
| 32 | #ifdef CONFIG_DYNAMIC_ALLOC | |
| 33 | struct cdev *cdev; | |
| 34 | #else | |
| 35 | struct cdev cdev; | |
| 36 | #endif | |
| 37 | ||
| 38 | static int chrdev_open (struct inode *inode, struct file *file) | |
| 39 | { | |
| 40 | return 0; | |
| 41 | } | |
| 42 | ||
| 43 | static int chrdev_close (struct inode *node, struct file *file) | |
| 44 | { | |
| 45 | return 0; | |
| 46 | } | |
| 47 | ||
| 48 | static struct file_operations chrdev_fops = { | |
| 49 | .owner = THIS_MODULE, | |
| 50 | .open = chrdev_open, /* open() implementation */ | |
| 51 | .release = chrdev_close, /* close() implementation */ | |
| 52 | }; | |
| 53 | ||
| 54 | static int __init chrdev_init(void) | |
| 55 | { | |
| 56 | dev_t devno; | |
| 57 | int rv; | |
| 58 | ||
| 59 | /* 1. Allocate device number */ | |
| 60 | if(0 != dev_major) | |
| 61 | { | |
| 62 | devno = MKDEV(dev_major, 0); | |
| 63 | rv = register_chrdev_region(devno, 1, DEV_NAME); | |
| 64 | } | |
| 65 | else | |
| 66 | { | |
| 67 | rv = alloc_chrdev_region(&devno, 0, 1, DEV_NAME); | |
| 68 | dev_major = MAJOR(devno); | |
| 69 | } | |
| 70 | ||
| 71 | if(rv < 0) | |
| 72 | { | |
| 73 | printk(KERN_ERR "%s driver can't use major %d\n", DEV_NAME, dev_major); | |
| 74 | return -ENODEV; | |
| 75 | } | |
| 76 | ||
| 77 | /* 2. Allocate and initialize cdev */ | |
| 78 | #ifdef CONFIG_DYNAMIC_ALLOC | |
| 79 | cdev = cdev_alloc(); | |
| 80 | if( !cdev ) | |
| 81 | { | |
| 82 | printk(KERN_ERR "Unable to allocate cdev\n"); | |
| 83 | goto failed1; | |
| 84 | } | |
| 85 | cdev_init(cdev, &chrdev_fops); | |
| 86 | #else | |
| 87 | cdev_init(&cdev, &chrdev_fops); | |
| 88 | cdev.owner = THIS_MODULE; | |
| 89 | #endif | |
| 90 | ||
| 91 | /* 3. Register cdev to linux kernel */ | |
| 92 | #ifdef CONFIG_DYNAMIC_ALLOC | |
| 93 | rv = cdev_add(cdev, devno, 1); | |
| 94 | #else | |
| 95 | rv = cdev_add(&cdev, devno, 1); | |
| 96 | #endif | |
| 97 | if( rv ) | |
| 98 | { | |
| 99 | rv = -ENODEV; | |
| 100 | printk(KERN_ERR "%s driver regist failed, rv=%d\n", DEV_NAME, rv); | |
| 101 | goto failed1; | |
| 102 | } | |
| 103 | ||
| 104 | printk(KERN_INFO "%s driver on major[%d] installed.\n", DEV_NAME, dev_major); | |
| 105 | return 0; | |
| 106 | ||
| 107 | failed1: | |
| 108 | unregister_chrdev_region(devno, 1); | |
| 109 | ||
| 110 | printk(KERN_ERR "%s driver installed failed.\n", DEV_NAME); | |
| 111 | return rv; | |
| 112 | } | |
| 113 | ||
| 114 | static void __exit chrdev_exit(void) | |
| 115 | { | |
| 116 | #ifdef CONFIG_DYNAMIC_ALLOC | |
| 117 | cdev_del(cdev); | |
| 118 | #else | |
| 119 | cdev_del(&cdev); | |
| 120 | #endif | |
| 121 | unregister_chrdev_region(MKDEV(dev_major,0), 1); | |
| 122 | ||
| 123 | printk(KERN_INFO "%s driver removed!\n", DEV_NAME); | |
| 124 | return; | |
| 125 | } | |
| 126 | ||
| 127 | module_init(chrdev_init); | |
| 128 | module_exit(chrdev_exit); | |
| 129 | ||
| 130 | MODULE_LICENSE("Dual BSD/GPL"); | |
| 131 | MODULE_AUTHOR("GuoWenxue <guowenxue@gmail.com>"); | |
