[Linux驱动]字符设备驱动学习笔记（三）———高级

一，ioctl使用实例

ioctl使用实例

驱动程序.h文件  memdev.h

/* 定义幻数 */
#define MEMDEV_IOC_MAGIC  'k'

/* 定义命令 */
#define MEMDEV_IOCPRINT   _IO(MEMDEV_IOC_MAGIC, 1)
#define MEMDEV_IOCGETDATA _IOR(MEMDEV_IOC_MAGIC, 2, int)
#define MEMDEV_IOCSETDATA _IOW(MEMDEV_IOC_MAGIC, 3, int)
#define MEMDEV_IOC_MAXNR 3

驱动程序.c文件

/*IO操作*/
int memdev_ioctl(struct inode *inode, struct file *filp,
                 unsigned int cmd, unsigned long arg)
{

    int err = 0;
    int ret = 0;
    int ioarg = 0;

    /* 检测命令的有效性 */
    if (_IOC_TYPE(cmd) != MEMDEV_IOC_MAGIC)
        return -EINVAL;
    if (_IOC_NR(cmd) > MEMDEV_IOC_MAXNR)
        return -EINVAL;

    /* 根据命令类型，检测参数空间是否可以访问 */
    if (_IOC_DIR(cmd) & _IOC_READ)
        err = !access_ok(VERIFY_WRITE, (void *)arg, _IOC_SIZE(cmd));
    else if (_IOC_DIR(cmd) & _IOC_WRITE)
        err = !access_ok(VERIFY_READ, (void *)arg, _IOC_SIZE(cmd));
    if (err)
        return -EFAULT;

    /* 根据命令，执行相应的操作 */
    switch(cmd) {

      /* 打印当前设备信息 */
      case MEMDEV_IOCPRINT:
          printk("<--- CMD MEMDEV_IOCPRINT Done--->

");
        break;

      /* 获取参数 */
      case MEMDEV_IOCGETDATA:
        ioarg = 1101;
        ret = __put_user(ioarg, (int *)arg);
        break;

      /* 设置参数 */
      case MEMDEV_IOCSETDATA:
        ret = __get_user(ioarg, (int *)arg);
        printk("<--- In Kernel MEMDEV_IOCSETDATA ioarg = %d --->

",ioarg);
        break;

      default:
        return -EINVAL;
    }
    return ret;

}

应用程序

#include "memdev.h"
    cmd = MEMDEV_IOCPRINT;
    if (ioctl(fd, cmd, &arg) < 0)
        {
            printf("Call cmd MEMDEV_IOCPRINT fail
");
            return -1;
    }
    cmd = MEMDEV_IOCSETDATA;
    arg = 2007;
    if (ioctl(fd, cmd, &arg) < 0)
        {
            printf("Call cmd MEMDEV_IOCSETDATA fail
");
            return -1;
    }