04clock_06semqphore

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 #include <linux/rwlock.h>  //读写自旋锁
 17 #include <linux/semaphore.h>
 18 
 19 /*
 20 该设备只能同时被一个进程打开
 21 */
 22 
 23 
 24 #define   DEVNAME  "my_led"
 25 #define  MEMSIZE  100
 26 
 27 
 28 int test = 1;
 29 
 30 struct ldm_info
 31 {
 32     struct  miscdevice dev;       //设备节点
 33     struct  file_operations  ops;  //文件操作
 34     unsigned char mem[MEMSIZE] ;  //数组, 内核的空间
 35     //rwlock_t  myrwlock;
 36     struct semaphore sema;
 37 };
 38 
 39 //struct ldm_info  ldm;
 40 struct ldm_info  ldm;  //结构体的指针,分配空间
 41 
 42 static  int ldm_open(struct inode * inode, struct file * file)
 43 {
 44     //printk("kernel: ldm_open\n");
 45     test++;
 46     //如何传递私有变量
 47     //Linux任何一个文件,都会有一个file指针,
 48     //有一个成员  private_data  void *   通用指针
 49     file->private_data =    (void *)&test;
 50 
 51     return 0;
 52 }
 53 
 54 /*
 55 copy_to_user
 56 copy_form_user
 57 */
 58 
 59 static  ssize_t ldm_write(struct file * file, const char __user * buf, size_t size, loff_t *   offt)
 60 {
 61     int i =0;
 62 
 63     int val = *(int *)file->private_data;
 64 
 65     //write_lock(&ldm.myrwlock);
 66     down(&ldm.sema);
 67     for(;i < size; i++) {
 68         //每拷贝一个字节,睡眠1s
 69         copy_from_user(ldm.mem + i, buf + i, 1);
 70         printk("write:%c  val = %d\n",  ldm.mem[i], val);
 71         ssleep(1); //延迟1s
 72     }
 73     //write_unlock(&ldm.myrwlock);
 74     up(&ldm.sema);
 75 
 76 
 77     return 0;
 78 }
 79 
 80 
 81 ssize_t ldm_read(struct file * file, char __user *  buf, size_t size, loff_t * offt)
 82 {
 83     //每隔一秒拷贝一个字节到用户层
 84     int i =0;
 85 
 86     int val = *(int *)file->private_data;
 87 
 88     //read_lock(&ldm.myrwlock);
 89     down(&ldm.sema);
 90     for(;i < size; i++) {
 91         //每拷贝一个字节,睡眠1s
 92         copy_to_user(buf + i, ldm.mem + i, 1);
 93         printk("read:%c, val = %d\n",  ldm.mem[i], val);
 94         ssleep(1); //延迟1s
 95     }
 96     //read_unlock(&ldm.myrwlock);
 97     up(&ldm.sema);
 98     return 0;
 99 }
100 
101 int ldm_release(struct inode * inode, struct file *file)
102 {
103     //printk("kernel: close\n");
104     test--;
105     return 0;
106 }
107 
108 static int test_init(void)
109 {
110     int ret = 0;
111 
112     printk("%s:%s:%d   init\n", __FILE__, __FUNCTION__, __LINE__);
113 
114 
115     ldm.dev.minor  = MISC_DYNAMIC_MINOR;  //系统自动分配次设备
116     ldm.dev.name = DEVNAME;//该名称将决定节点名称, 成功注册 linux 系统中
117     ldm.dev.fops = &ldm.ops;  //关联文件操作
118     ldm.ops.open = ldm_open;
119     ldm.ops.write = ldm_write;
120     ldm.ops.read = ldm_read;
121     ldm.ops.release = ldm_release;
122 
123 
124     ret = misc_register(&ldm.dev);
125 
126     //rwlock_init(&ldm.myrwlock);
127     sema_init(&ldm.sema, 1); 
128 
129     if(ret < 0) {
130         printk("misc_register  failed\n");
131         goto  err_misc_register;
132     }
133 
134     return 0;
135 err_misc_register:
136     return ret;
137 
138 }
139 
140 //卸载
141 static void test_exit(void)
142 {
143     printk("%s:%s:%d   init\n", __FILE__, __FUNCTION__, __LINE__);
144 
145 
146     //注销misc 
147     misc_deregister(&ldm.dev);
148     //释放映射的虚拟地址
149 
150 }
151 
152 module_init(test_init);
153 module_exit(test_exit);
154 
155 
156 MODULE_LICENSE("GPL");  //加入GPL许可