04lock_05seqlock

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/seqlock.h>  //顺序锁
 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     seqlock_t   seq;
 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     write_seqlock(&ldm.seq);
 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     write_sequnlock(&ldm.seq);
 75 
 76     return 0;
 77 }
 78 
 79 
 80 ssize_t ldm_read(struct file * file, char __user *  buf, size_t size, loff_t * offt)
 81 {
 82     //每隔一秒拷贝一个字节到用户层
 83     int i =0;
 84 
 85     int val = *(int *)file->private_data;
 86 
 87     int seq = 0;
 88     do {
 89         seq = read_seqbegin(&ldm.seq);
 90         //printk("seq = %d\n", seq);
 91 
 92         for(;i < size; i++) {
 93             //seq = read_seqbegin(&ldm.seq);
 94             //每拷贝一个字节,睡眠1s
 95             copy_to_user(buf + i, ldm.mem + i, 1);
 96             printk("read:%c, val = %d\n",  ldm.mem[i], val);
 97             ssleep(1); //延迟1s
 98         }
 99     }while(read_seqretry(&ldm.seq, seq));
100     
101     return 0;
102 }
103 
104 int ldm_release(struct inode * inode, struct file *file)
105 {
106     //printk("kernel: close\n");
107     test--;
108     return 0;
109 }
110 
111 static int test_init(void)
112 {
113     int ret = 0;
114 
115     printk("%s:%s:%d   init\n", __FILE__, __FUNCTION__, __LINE__);
116 
117 
118     ldm.dev.minor  = MISC_DYNAMIC_MINOR;  //系统自动分配次设备
119     ldm.dev.name = DEVNAME;//该名称将决定节点名称, 成功注册 linux 系统中
120     ldm.dev.fops = &ldm.ops;  //关联文件操作
121     ldm.ops.open = ldm_open;
122     ldm.ops.write = ldm_write;
123     ldm.ops.read = ldm_read;
124     ldm.ops.release = ldm_release;
125 
126 
127     ret = misc_register(&ldm.dev);
128 
129     //rwlock_init(&ldm.myrwlock);
130     seqlock_init(&ldm.seq);
131 
132     if(ret < 0) {
133         printk("misc_register  failed\n");
134         goto  err_misc_register;
135     }
136 
137     return 0;
138 err_misc_register:
139     return ret;
140 
141 }
142 
143 //卸载
144 static void test_exit(void)
145 {
146     printk("%s:%s:%d   init\n", __FILE__, __FUNCTION__, __LINE__);
147 
148 
149     //注销misc 
150     misc_deregister(&ldm.dev);
151     //释放映射的虚拟地址
152 
153 }
154 
155 module_init(test_init);
156 module_exit(test_exit);
157 
158 
159 MODULE_LICENSE("GPL");  //加入GPL许可