Linux驱动基础

#include <linux/kernel.h>
#include  
#include  
//#include
//#include
#include ioctl.h>  // 这个头文件可能定义了 unlocked_ioctl 的类型

#define MY_IOCTL_CMD 0x99
#define MY_IOCTL_TYPE 0x99

static int Major; // 主设备号  
static char msg[256]; // 存储消息的缓冲区  
static char *msg_Ptr; // 当前写入的位置  

void test(void)
{
    return ;
}
EXPORT_SYMBOL(test);

static int hello_open(struct inode *inode, struct file *file)  
{
    test();    
    return 0;  
}  
  
static int hello_read(struct file *filp, char *buffer, size_t length, loff_t * offset)  
{  
    int bytes_read = 0;  
    if (*msg_Ptr == 0) return 0; // 如果没有数据可读，返回0  
    while (length && *msg_Ptr) {  
        put_user(*(msg_Ptr++), buffer++); // 将数据复制到用户空间  
        length--;  
        bytes_read++;  
    }  
    return bytes_read;  
}  
  
static int hello_write(struct file *filp, const char *buff, size_t len, loff_t * off)  
{  
    int total_written = 0;  
    while (len) {  
        char c;  
        get_user(c, buff); // 从用户空间读取数据  
        *(msg_Ptr++) = c; // 将数据写入到消息缓冲区中  
        len--;  
        total_written++;  
        buff++;  
    }  
    return total_written;  
}  

static long hello_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)  
{
      printk("hsm ioctl");
      if (_IOC_TYPE(cmd) != 0x99)
        return -ENOTTY;
      else
          printk("ok.......");
    
      return 0;
}

static int hello_release(struct inode *inode, struct file *file)  
{  
    msg_Ptr = msg; // 重置消息指针到开始位置，以便下一次写入可以从开始位置开始  
    return 0;  
}  

static struct file_operations hello_fops = {   
  //  .read = hello_read,    
  //  .write = hello_write,    
  //  .open = hello_open,    
  //  .release = hello_release,    
    .unlocked_ioctl = hello_ioctl, 
}; 

static int hello_init(void) {  
    Major = register_chrdev(0, "my_dev", &hello_fops);  
    if (Major < 0) {  
        printk(KERN_ALERT "Registering char device failed with %d\n", Major);  
        return Major;  
    }  
    printk(KERN_INFO "I was assigned major number %d. To talk to the driver, create a dev file with 'mknod /dev/my_dev c %d 0'.\n", Major, Major);  
    return 0;  
}  
  
static void hello_exit(void) {  
    unregister_chrdev(Major, "my_dev");  
    printk(KERN_INFO "Unregistered and removed /dev/my_dev.\n");  
}  
  
module_init(hello_init);
module_exit(hello_exit);
MODULE_LICENSE("GPL");
 

obj-m := driver.o

KERNELDIR ?= /lib/modules/$(shell uname -r)/build
#KERNELDIR ?= /root/linux-4.19.90-all-arch-master
PWD       := $(shell pwd)

default:
    $(MAKE) -C ${KERNELDIR} M=$(PWD)  modules
clean:
    rm *.o *.ko *.symvers *.order *.mod.c .*.cmd .tmp_versions/ -rf

#include
#include
#include
#include

#define MY_DEVICE_TYPE 0x99
#define MY_IOCTL_CMD  _IOWR (MY_DEVICE_TYPE, 0x99, unsigned long)

int main()
{
    int fd = open("/dev/my_dev", O_RDWR); // 替换为你的设备名  
    if (fd < 0) {  
        perror("open");  
        return -1;  
    }  
    if (ioctl(fd, MY_IOCTL_CMD, "hello") < 0) {  
        perror("ioctl");
        close(fd);  
        return -1;  
    }  
    printf("succ!\n");
    close(fd); // 别忘了关闭文件描述符！
    return -1;
}
 

OBJ=app

$(OBJ): app.c
    gcc app.c -o app

.PHONY:clean

clean:
    rm -rf app