模块参数使用示例

#include <linux/module.h>
#include <linux/moduleparam.h> /* Optional, to include module_param() macros */
#include <linux/kernel.h> /* Optional, to include prink() prototype */
#include <linux/init.h> /* Optional, to include module_init() macros */
#include <linux/stat.h> /* Optional, to include S_IRUSR ... */

static int myint = -99;
static char *mystring = "i'm hungry";

static int myintary[]= {1,2,3,4};
static char *mystrary[] = {"apple", "orange", "banana"};
static int nstrs = 3;

module_param(myint, int, S_IRUSR|S_IWUSR);
MODULE_PARM_DESC(myint, "A trial integer");

module_param(mystring, charp, 0);
module_param_array(myintary, int, NULL, 0444);
module_param_array(mystrary, charp, &nstrs, 0664);

static int __init hello_init(void)
{
int i;

printk(KERN_INFO "myint is %d/n", myint);
printk(KERN_INFO "mystring is %s/n", mystring);

printk(KERN_INFO "myintary are");
for(i = 0; i < sizeof(myintary)/sizeof(int); i++)
printk(" %d", myintary[i]);
printk("/n");

printk(KERN_INFO "mystrary are");
for(i=0; i < nstrs; i++)
printk(" %s", mystrary[i]);
printk("/n");

return 0;
}

static void __exit hello_exit(void)
{
}

module_init(hello_init);
module_exit(hello_exit);

运行：
insmod ./hello.ko myint=100 mystring="abc" myintary=-1,-2 mystrary="a","b"

dmesg输出：
myint is 100
mystring is abc
myintary are -1 -2 3 4
mystrary are a b

说明：
module_param() 和 module_param_array() 的作用就是让那些全局变量对 insmod 可见，使模块装载时可重新赋值。
module_param_array() 宏的第三个参数用来记录用户 insmod 时提供的给这个数组的元素个数，NULL 表示不关心用户提供的个数
module_param() 和 module_param_array() 最后一个参数权限值不能包含让普通用户也有写权限，否则编译报错。这点可参考 linux/moduleparam.h 中 __module_param_call() 宏的定义。
字符串数组中的字符串似乎不能包含逗号，否则一个字符串会被解析成两个