IOCTL Linux 设备驱动程序 [英] IOCTL Linux device driver

问题描述

谁能给我解释一下，

1. 什么是IOCTL?
2. 它有什么用?
3. 我该如何使用它?
4. 为什么我不能定义与 IOCTL 一样工作的新函数?

1. What is IOCTL?
2. What is it used for?
3. How can I use it?
4. Why can't I define new function that does the same work as IOCTL?

推荐答案

一个ioctl，意思是输入-输出控制"是一种特定于设备的系统调用.Linux 中只有少数系统调用(300-400)，不足以表达设备可能具有的所有独特功能.因此，驱动程序可以定义一个 ioctl，它允许用户空间应用程序向它发送命令.然而，ioctl 不是很灵活，而且往往会变得有点混乱(几十个神奇数字"不管用……还是不行)，而且也可能不安全，因为您将缓冲区传递给内核 - 处理不当可能会破坏事情很容易.

An ioctl, which means "input-output control" is a kind of device-specific system call. There are only a few system calls in Linux (300-400), which are not enough to express all the unique functions devices may have. So a driver can define an ioctl which allows a userspace application to send it orders. However, ioctls are not very flexible and tend to get a bit cluttered (dozens of "magic numbers" which just work... or not), and can also be insecure, as you pass a buffer into the kernel - bad handling can break things easily.

另一种方法是 sysfs 接口，您可以在其中设置 /sys/ 下的文件，然后读取/写入该文件以从驱动程序获取信息以及向驱动程序获取信息.如何设置的示例:

An alternative is the sysfs interface, where you set up a file under /sys/ and read/write that to get information from and to the driver. An example of how to set this up:

static ssize_t mydrvr_version_show(struct device *dev,
        struct device_attribute *attr, char *buf)
{
    return sprintf(buf, "%s
", DRIVER_RELEASE);
}

static DEVICE_ATTR(version, S_IRUGO, mydrvr_version_show, NULL);

在驱动程序设置期间:

device_create_file(dev, &dev_attr_version);

然后，您将在 /sys/ 中为您的设备创建一个文件，例如，/sys/block/myblk/version 用于块驱动程序.

You would then have a file for your device in /sys/, for example, /sys/block/myblk/version for a block driver.

另一种更频繁使用的方​​法是 netlink，它是一种 IPC(进程间通信)方法，可通过 BSD 套接字接口与驱动程序通信.例如，这由 WiFi 驱动程序使用.然后，您可以使用 libnl 或 libnl3 库从用户空间与它通信.

Another method for heavier use is netlink, which is an IPC (inter-process communication) method to talk to your driver over a BSD socket interface. This is used, for example, by the WiFi drivers. You then communicate with it from userspace using the libnl or libnl3 libraries.

这篇关于IOCTL Linux 设备驱动程序的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！