1 #include <linux/module.h> //MODULE_LICENSE("GPL");
2 #include <linux/init.h> //module_init module_exit
3 #include <linux/kernel.h> //printk
4 #include <linux/io.h> //ioremap iounremap
5 #include <linux/ioport.h> //request_mem_region
6
7
8 #include <linux/miscdevice.h>
9 #include <linux/fs.h> //file_operations 结构体的定义
10 #include <linux/slab.h> //kmalloc
11 #include <linux/delay.h>
12
13 #include <asm/uaccess.h> //copy_to_user copy_form_user
14 #include <asm/atomic.h>
15
16 /*
17 该设备只能同时被一个进程打开
18 */
19
20
21 #define DEVNAME "my_led"
22 #define MEMSIZE 100
23
24 struct ldm_info
25 {
26 struct miscdevice dev; //设备节点
27 struct file_operations ops; //文件操作
28 unsigned char mem[MEMSIZE] ; //数组, 内核的空间
29 atomic_t atomic; //原子变量,用于防止多个进程同时打开
30 };
31
32 //struct ldm_info ldm;
33 struct ldm_info ldm; //结构体的指针,分配空间
34
35 static int ldm_open(struct inode * inode, struct file * file)
36 {
37 printk("kernel: ldm_open\n");
38 //先自减 test
39 if(!atomic_dec_and_test(&ldm.atomic)) {
40 atomic_inc(&ldm.atomic);
41 return -1;
42 }
43
44 return 0;
45 }
46
47 /*
48 copy_to_user
49 copy_form_user
50 */
51
52 static ssize_t ldm_write(struct file * file, const char __user * buf, size_t size, loff_t * offt)
53 {
54 int i =0;
55 for(;i < size; i++) {
56 //每拷贝一个字节,睡眠1s
57 copy_from_user(ldm.mem + i, buf + i, 1);
58 printk("write:%c\n", ldm.mem[i]);
59 ssleep(1); //延迟1s
60 }
61
62 return 0;
63 }
64
65
66 ssize_t ldm_read(struct file * file, char __user * buf, size_t size, loff_t * offt)
67 {
68 //每隔一秒拷贝一个字节到用户层
69 int i =0;
70 for(;i < size; i++) {
71 //每拷贝一个字节,睡眠1s
72 copy_to_user(buf + i, ldm.mem + i, 1);
73 printk("read:%c\n", ldm.mem[i]);
74 ssleep(1); //延迟1s
75 }
76
77 return 0;
78 }
79
80 int ldm_release(struct inode * inode, struct file *file)
81 {
82 printk("kernel: close\n");
83 atomic_inc(&ldm.atomic); //+1
84 return 0;
85 }
86
87 static int test_init(void)
88 {
89 int ret = 0;
90
91 printk("%s:%s:%d init\n", __FILE__, __FUNCTION__, __LINE__);
92
93
94 ldm.dev.minor = MISC_DYNAMIC_MINOR; //系统自动分配次设备
95 ldm.dev.name = DEVNAME;//该名称将决定节点名称, 成功注册 linux 系统中
96 ldm.dev.fops = &ldm.ops; //关联文件操作
97 ldm.ops.open = ldm_open;
98 ldm.ops.write = ldm_write;
99 ldm.ops.read = ldm_read;
100 ldm.ops.release = ldm_release;
101
102
103 ret = misc_register(&ldm.dev);
104
105 //原子变量 初始化为1
106 atomic_set(&ldm.atomic, 1);
107
108 if(ret < 0) {
109 printk("misc_register failed\n");
110 goto err_misc_register;
111 }
112
113 return 0;
114 err_misc_register:
115 return ret;
116
117 }
118
119 //卸载
120 static void test_exit(void)
121 {
122 printk("%s:%s:%d init\n", __FILE__, __FUNCTION__, __LINE__);
123
124
125 //注销misc
126 misc_deregister(&ldm.dev);
127 //释放映射的虚拟地址
128
129 }
130
131 module_init(test_init);
132 module_exit(test_exit);
133
134
135 MODULE_LICENSE("GPL"); //加入GPL许可
