Linux内核驱动模块编程指南详解

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"Linux内核驱动模块编程指南" 《Linux内核驱动模块编程指南》是一本由Peter Jay Salzman、Michael Burian和Ori Pomerantz合著的专业书籍，专注于介绍如何在Linux系统中编写和管理内核驱动程序。这本书遵循开源软件许可证（Open Software License 1.1）的规定，鼓励读者自由复制、修改并分发，只要保留原始的版权信息。该指南的核心内容可能涵盖了以下几个关键知识点： 1. **内核模块基础**：首先会介绍Linux内核模块的基本概念，包括内核模块的结构、生命周期和加载机制。学习者会了解到如何创建、编译和加载一个简单的内核模块，并理解模块的初始化和退出函数。 2. **内核数据结构和API**：书中详细讲解了Linux内核中常用的数据结构，如链表、队列、哈希表等，以及与之相关的API接口。这些数据结构和API是编写驱动程序的基础，用于在内核空间中进行数据管理和操作。 3. **设备模型**：在Linux内核中，设备通常通过设备模型来抽象和管理。书中可能会涵盖总线、设备、驱动三者的关联，以及如何注册和管理设备节点。 4. **中断处理和中断驱动**：中断是硬件与内核通信的关键机制。书中会讨论中断处理程序的编写，以及中断上下文中的限制和注意事项。 5. **I/O端口和内存映射**：驱动开发往往涉及到I/O端口的读写或内存映射。这部分内容会讲解如何访问硬件寄存器，以及如何正确地在内核中进行内存管理。 6. **字符设备和块设备驱动**：对于不同的设备类型，如字符设备和块设备，书中会详细介绍对应的驱动模型和API，如何实现read、write等基本操作。 7. **网络驱动程序**：如果深入，可能会涉及网络驱动的编程，包括网络协议栈的理解，以及如何编写网络设备驱动，如以太网驱动。 8. **文件系统和文件操作**：在某些情况下，驱动可能需要与文件系统交互。这部分将解释如何实现VFS（虚拟文件系统）接口，以及文件操作函数。 9. **并发和同步**：由于内核是多线程环境，所以同步原语（如自旋锁、信号量、原子操作等）的使用至关重要。这部分内容会讲解如何避免数据竞争和死锁。 10. **调试技术**：内核驱动的调试往往比用户空间程序更为复杂，书中可能介绍使用`kdb`、`kgdb`、`printk`等工具进行内核级别的调试。这本书不仅适合有C语言基础的开发者，也适合对Linux系统有一定了解并希望深入到内核层面对硬件进行控制的工程师。通过学习，读者能够具备编写和维护Linux内核驱动的能力，从而更好地适应各种硬件环境和需求。

printk(KERN_INFO "Hello, world 4\n");

return 0;

}

static void __exit cleanup_hello_4(void)

{

printk(KERN_INFO "Goodbye, world 4\n");

}

module_init(init_hello_4);

module_exit(cleanup_hello_4);

* You can use strings, like this:

* Get rid of taint message by declaring code as GPL.

MODULE_LICENSE("GPL");

* Or with defines, like this:

MODULE_AUTHOR(DRIVER_AUTHOR); /* Who wrote this module? */

MODULE_DESCRIPTION(DRIVER_DESC); /* What does this module do */

* This module uses /dev/testdevice. The MODULE_SUPPORTED_DEVICE macro might

* be used in the future to help automatic configuration of modules, but is

* currently unused other than for documentation purposes.

MODULE_SUPPORTED_DEVICE("testdevice");

2.6. Passing Command Line Arguments to a Module

Modules can take command line arguments, but not with the argc/argv you might be used to.

To allow arguments to be passed to your module, declare the variables that will take the values of the

command line arguments as global and then use the module_param() macro, (defined in

linux/moduleparam.h) to set the mechanism up. At runtime, insmod will fill the variables with any

command line arguments that are given, like ./insmod mymodule.ko myvariable=5. The variable

declarations and macros should be placed at the beginning of the module for clarity. The example code should

clear up my admittedly lousy explanation.

The module_param() macro takes 3 arguments: the name of the variable, its type and permissions for the

corresponding file in sysfs. Integer types can be signed as usual or unsigned. If you'd like to use arrays of

integers or strings see module_param_array() and module_param_string().

int myint = 3;

module_param(myint, int, 0);

Arrays are supported too, but things are a bit different now than they were in the 2.4. days. To keep track of

the number of parameters you need to pass a pointer to a count variable as third parameter. At your option,

you could also ignore the count and pass NULL instead. We show both possibilities here:

The Linux Kernel Module Programming Guide

Chapter 2. Hello World 11

int myintarray[2];

module_param_array(myintarray, int, NULL, 0); /* not interested in count */

int myshortarray[4];

int count;

module_parm_array(myshortarray, short, , 0); /* put count into "count" variable */

A good use for this is to have the module variable's default values set, like an port or IO address. If the

variables contain the default values, then perform autodetection (explained elsewhere). Otherwise, keep the

current value. This will be made clear later on.

Lastly, there's a macro function, MODULE_PARM_DESC(), that is used to document arguments that the

module can take. It takes two parameters: a variable name and a free form string describing that variable.

Example 2−7. hello−5.c

* hello−5.c − Demonstrates command line argument passing to a module.

#include <linux/module.h>

#include <linux/moduleparam.h>

#include <linux/kernel.h>

#include <linux/init.h>

#include <linux/stat.h>

MODULE_LICENSE("GPL");

MODULE_AUTHOR("Peter Jay Salzman");

static short int myshort = 1;

static int myint = 420;

static long int mylong = 9999;

static char *mystring = "blah";

static int myintArray[2] = { −1, −1 };

static int arr_argc = 0;

* module_param(foo, int, 0000)

* The first param is the parameters name

* The second param is it's data type

* The final argument is the permissions bits,

* for exposing parameters in sysfs (if non−zero) at a later stage.

module_param(myshort, short, S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP);

MODULE_PARM_DESC(myshort, "A short integer");

module_param(myint, int, S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH);

MODULE_PARM_DESC(myint, "An integer");

module_param(mylong, long, S_IRUSR);

MODULE_PARM_DESC(mylong, "A long integer");

module_param(mystring, charp, 0000);

MODULE_PARM_DESC(mystring, "A character string");

* module_param_array(name, type, num, perm);

* The first param is the parameter's (in this case the array's) name

* The second param is the data type of the elements of the array

* The third argument is a pointer to the variable that will store the number

* of elements of the array initialized by the user at module loading time

* The fourth argument is the permission bits

The Linux Kernel Module Programming Guide

Chapter 2. Hello World 12

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