04lock_03spin_lock

Posted 2020-08-31 莽莽丛林

  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 
 15 #include <linux/spinlock.h>  //自旋锁
 16 
 17 /*
 18 该设备只能同时被一个进程打开
 19 */
 20 
 21 
 22 #define   DEVNAME  "my_led"
 23 #define  MEMSIZE  100
 24 
 25 struct ldm_info
 26 {
 27     struct  miscdevice dev;       //设备节点
 28     struct  file_operations  ops;  //文件操作
 29     unsigned char mem[MEMSIZE] ;  //数组, 内核的空间
 30     spinlock_t  mylock;  //自旋锁
 31 };
 32 
 33 //struct ldm_info  ldm;
 34 struct ldm_info  ldm;  //结构体的指针,分配空间
 35 
 36 static  int ldm_open(struct inode * inode, struct file * file)
 37 {
 38     printk("kernel: ldm_open\n");
 39 
 40     return 0;
 41 }
 42 
 43 /*
 44 copy_to_user
 45 copy_form_user
 46 */
 47 
 48 static  ssize_t ldm_write(struct file * file, const char __user * buf, size_t size, loff_t *   offt)
 49 {
 50     int i =0;
 51 
 52     spin_lock(&ldm.mylock);
 53     //临界区开始
 54 
 55     // if(!spin_trylock(&ldm.mylock)) {
 56     //     printk("当前资源被占用,请稍后\n");
 57     //     return -1;
 58     // }
 59 
 60     for(;i < size; i++) {
 61         //每拷贝一个字节,睡眠1s
 62         copy_from_user(ldm.mem + i, buf + i, 1);
 63         printk("write:%c\n",  ldm.mem[i]);
 64         ssleep(1); //延迟1s
 65     }
 66     spin_unlock(&ldm.mylock);
 67     //临界区结束
 68 
 69     return 0;
 70 }
 71 
 72 
 73 ssize_t ldm_read(struct file * file, char __user *  buf, size_t size, loff_t * offt)
 74 {
 75     //每隔一秒拷贝一个字节到用户层
 76     int i =0;
 77 
 78     spin_lock(&ldm.mylock);
 79     // if(!spin_trylock(&ldm.mylock)) {
 80     //     printk("当前资源被占用,请稍后\n");
 81     //     return -1;
 82     // }
 83 
 84     for(;i < size; i++) {
 85         //每拷贝一个字节,睡眠1s
 86         copy_to_user(buf + i, ldm.mem + i, 1);
 87         printk("read:%c\n",  ldm.mem[i]);
 88         ssleep(1); //延迟1s
 89     }
 90     spin_unlock(&ldm.mylock);
 91 
 92 
 93     return 0;
 94 }
 95 
 96 int ldm_release(struct inode * inode, struct file *file)
 97 {
 98     printk("kernel: close\n");
 99 
100     return 0;
101 }
102 
103 static int test_init(void)
104 {
105     int ret = 0;
106 
107     printk("%s:%s:%d   init\n", __FILE__, __FUNCTION__, __LINE__);
108 
109 
110     ldm.dev.minor  = MISC_DYNAMIC_MINOR;  //系统自动分配次设备
111     ldm.dev.name = DEVNAME;//该名称将决定节点名称, 成功注册 linux 系统中
112     ldm.dev.fops = &ldm.ops;  //关联文件操作
113     ldm.ops.open = ldm_open;
114     ldm.ops.write = ldm_write;
115     ldm.ops.read = ldm_read;
116     ldm.ops.release = ldm_release;
117 
118 
119     ret = misc_register(&ldm.dev);
120 
121     spin_lock_init(&ldm.mylock);//初始化自旋锁
122 
123     if(ret < 0) {
124         printk("misc_register  failed\n");
125         goto  err_misc_register;
126     }
127 
128     return 0;
129 err_misc_register:
130     return ret;
131 
132 }
133 
134 //卸载
135 static void test_exit(void)
136 {
137     printk("%s:%s:%d   init\n", __FILE__, __FUNCTION__, __LINE__);
138 
139 
140     //注销misc 
141     misc_deregister(&ldm.dev);
142     //释放映射的虚拟地址
143 
144 }
145 
146 module_init(test_init);
147 module_exit(test_exit);
148 
149 
150 MODULE_LICENSE("GPL");  //加入GPL许可