求助驱动开发中，ioctl的问题

尘然 · 发表于 2022-5-10 09:23:23

先看代码：

1、驱动程序：

#include <linux/module.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/cdev.h>
#include <linux/device.h>
#include <asm/uaccess.h>

#define TIMER_DEV_NAME  "test"
#define TIMER_DEV_COUNT 1

#define CMD_RUN    (_IO('T', 0x54))
#define CMD_STOP (_IO('T', 0x53))

struct timer_dev_type {
dev_t dev_id;
struct cdev cdev;
struct class *class;
struct device *device;
int major;
};
struct timer_dev_type timer_dev;

static int timer_dev_open(struct inode *inode, struct file *file)
{
return 0;
}

long timer_dev_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
switch(cmd)
{
      case CMD_RUN:
         printk("Running!\n");
         break;
      case CMD_STOP:
         printk("Stopped!\n");
         break;
}

return 0;
}

static struct file_operations timer_dev_ops = {
.owner = THIS_MODULE,
.open = timer_dev_open,
.unlocked_ioctl = timer_dev_ioctl,
};

static int __init timer_dev_init(void)
{
int err = 0;

/* 1、创建设备号 */
if(timer_dev.major)
{
      timer_dev.dev_id = MKDEV(timer_dev.major, 0);
      register_chrdev_region(timer_dev.dev_id, TIMER_DEV_COUNT, TIMER_DEV_NAME);
}
else
{
      alloc_chrdev_region(&timer_dev.dev_id, 0, TIMER_DEV_COUNT, TIMER_DEV_NAME);
      timer_dev.major = MAJOR(timer_dev.dev_id);
}

/* 2、初始并添加字符设备 */
timer_dev.cdev.owner = THIS_MODULE;
cdev_init(&timer_dev.cdev, &timer_dev_ops);
cdev_add(&timer_dev.cdev, timer_dev.dev_id, TIMER_DEV_COUNT);

/* 3、创建类 */
timer_dev.class = class_create(THIS_MODULE, TIMER_DEV_NAME);
if(IS_ERR(timer_dev.class))
{
      printk("Error: Failed to create timer class!\n");
      return -EINVAL;
}

/* 4、创建设备 */
timer_dev.device = device_create(timer_dev.class, NULL, timer_dev.dev_id, NULL, TIMER_DEV_NAME);
if(IS_ERR(timer_dev.device))
{
      printk("Error: Failed to create device!\n");
      return -EINVAL;
}

return err;
}

static void __exit timer_dev_exit(void)
{
/* 1、删除设备 */
device_destroy(timer_dev.class, timer_dev.dev_id);
/* 2、删除类 */
class_destroy(timer_dev.class);
/* 3、注销字符设备 */
cdev_del(&timer_dev.cdev);
/* 4、释放设备号 */
unregister_chrdev_region(timer_dev.dev_id, TIMER_DEV_COUNT);
}

module_init(timer_dev_init);
module_exit(timer_dev_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("LSW");

2、应用程序：

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>

#define CMD_RUN    (_IO('T', 0x54))
#define CMD_STOP (_IO('T', 0x53))

int main(int argc, char const *argv[])
{
int err = 0;
int fd;
const char *filename = argv[1];
unsigned char cmd;

/* 打开文件 */
fd = open(filename, O_RDWR);
if(fd < 0)
{
      printf("Error: Could not open file: %s\n", filename);
      return -1;
}

#if 0 /* 代码1：直接调用ioctl */
/* 能成功实现 */
ioctl(fd, CMD_RUN);
ioctl(fd, CMD_STOP);

#else /* 代码2：通过键盘输入命令，再通过命令调用ioctl */
/* 不能实现 */
printf("Please input cmd:");
err = scanf("%d", &cmd);
if(err != 1)       // 防止卡死
{
      while(getchar() != '\n');
}

if(cmd == 1)
{
      err = ioctl(fd, CMD_RUN);
      if(err != 0)
      {
         printf("ioctl error: %d\n", err);
      }
      printf("cmd1 executed!\n");
}
else if(cmd == 2)
{
      err = ioctl(fd, CMD_STOP);
      if(err != 0)
      {
         printf("ioctl error: %d\n", err);
      }
      printf("cmd2 executed!\n");
}
#endif

/* 关闭文件 */
err = close(fd);
if(err < 0)
{
      printf("Error: Could not close file: %s\n");
      return -1;
}

return 0;
}

问题描述

在应用程序中，如果直接调用ioctl函数（代码1）时，驱动程序中的ioctl能成功打印，

但是，如果应用程序中，用代码2来调用时，虽然没有报错，但是就是没有代用到驱动程序的ioctl