Linux内核模块编程入门-5（传递命令行参数到模块）
模块可以接受命令行参数，但是不是使用argc/argv。
为了让参数传递到模块中，声明变量来存放命令行参数作为全局变量，然后使用module_param()宏来建立该机制，该宏定义在linux/moduleprarm.h中。在运行时，insmod将使用任何的命令行参数，像insmod mymodule.ko myvariable=5来填充参数。为清楚起见，变量声明和宏应该放在模块的开头，下例代码清晰地展示了模块接受命令行参数的用法
module_param()宏接受3个参数：变量名，变量类型和sysfs中相应文件的权限。整型可以是普通整型或无符号整型。若要使用整型数组或字符串，则需要参考module_param_array()和module_param_string()。
int myint = 3; module_param(myint, int, 0);
数组参数也是支持的。为了跟踪参数的数目，需要传递一个指向count变量的指针作为第三个参数。该参数是可选的，可以忽略该count变量，传递NULL来代替。
int myintarray[2]; module_param_array(myintarray, int, NULL, 0); // not interested in count int myshortarray[4]; int count; module_param_array(myshortarray, short, , 0); // put count int "count" variable
最后，有一个宏函数，MODULE_PARAM_DESC()，用来记录模块使用的参数，它有两个参数：变量名和自由格式字符串用来描述变量。
以下是示例：
/*
* hello-4.c - Demonstrates command line argument passing to a module.
*/
#include <linux/module.h> // Needed by all modules
#include <linux/kernel.h> // Needed for KERN_INFO
#include <linux/init.h> // Needed for the macros
#include <linux/moduleparam.h>
#include <linux/stat.h>
#define DRIVER_AUTHOR "Fantasy<@gmail.com>"
#define DRIVER_DESC "A simple driver"
MODULE_LICENSE("GPL");
MODULE_AUTHOR(DRIVER_AUTHOR);
MODULE_DESCRIPTION(DRIVER_DESC);
MODULE_SUPPORTED_DEVICE("testdevice");
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_IRGRP);
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 parameters'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
*/
module_param_array(myintarray, int, &arr_argc, 0000);
MODULE_PARM_DESC(myintArray, "An array of integers");
static int __init hello_5_init(void)
{
int i;
printk(KERN_INFO "Hello, World 5\n====================\n");
printk(KERN_INFO "myshort is a short integer:%hd\n", myshort);
printk(KERN_INFO "myint is an integer:%d\n", myint);
printk(KERN_INFO "mylong is a long integer:%ld\n", mylong);
printk(KERN_INFO "mystring is a string:%s\n", mystring);
for(i = 0; i < (sizeof myintarray / sizeof(int)); i++)
{
printk(KERN_INFO "myintArray[%d] = %d\n", i, myintarray[i]);
}
printk(KERN_INFO "got %d arguments for myintArray.\n", arr_argc);
return 0;
}
static void __exit hello_5_exit(void)
{
printk(KERN_INFO "Goodbye, world 5\n");
}
module_init(hello_5_init);
module_exit(hello_5_exit);
输入如下命令时：
insmod hello_5.ko mystring="Fantasy" myshort=25 myintarray=20输出为（通过vim /var/log/syslog查看）：
输入如下命令时：
insmod hello_5.ko mystring="Fantasy" myshort=25 mylong=10000 myint=100 myintarray=20,30输出为：
以上示例运行的Linux为：
root@ubuntu:/home/administrator/LKMP/ch2/hello_5# uname -a Linux ubuntu 3.8.0-29-generic #42~precise1-Ubuntu SMP Wed Aug 14 16:19:23 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux