1.引入module_param目的。
在用户态下编程可以通过main()来传递命令行参数，而编写一个内核模块则可通过module_param()来传递命令行参数. 也就是内核允许对驱动程序在加载的时候传递参数，e.g.insmod hello who="world" times=5 其中who，times 均为要传递的参数变量。
2.module_param()的定义 。
module_param宏是Linux 2.6内核中新增的，该宏被定义在include/linux/moduleparam.h文件中，具体定义如下（我从源码那里找来的http://tomoyo./cgi-bin/lxr/source/include/linux/moduleparam.h）：
/**
77 * module_param - typesafe helper for a module/cmdline parameter
78 * @value: the variable to alter, and exposed parameter name.
79 * @type: the type of the parameter
80 * @perm: visibility in sysfs.
81 *
82 * @value becomes the module parameter, or (prefixed by KBUILD_MODNAME and a
83 * ".") the kernel commandline parameter. Note that - is changed to _, so
84 * the user can use "foo-bar=1" even for variable "foo_bar".
85 *
86 * @perm is 0 if the the variable is not to appear in sysfs, or 0444
87 * for world-readable, 0644 for root-writable, etc. Note that if it
88 * is writable, you may need to use kparam_block_sysfs_write() around
89 * accesses (esp. charp, which can be kfreed when it changes).
90 *
91 * The @type is simply pasted to refer to a param_ops_##type and a
92 * param_check_##type: for convenience many standard types are provided but
93 * you can create your own by defining those variables.
94 *
95 * Standard types are:
96 * byte, short, ushort, int, uint, long, ulong
97 * charp: a character pointer
98 * bool: a bool, values 0/1, y/n, Y/N.
99 * invbool: the above, only sense-reversed (N = true).
100 */
101 #define module_param(name, type, perm) /
102 module_param_named(name, name, type, perm)
103
104 /**
105 * module_param_named - typesafe helper for a renamed module/cmdline parameter
106 * @name: a valid C identifier which is the parameter name.
107 * @value: the actual lvalue to alter.
108 * @type: the type of the parameter
109 * @perm: visibility in sysfs.
110 *
111 * Usually it's a good idea to have variable names and user-exposed names the
112 * same, but that's harder if the variable must be non-static or is inside a
113 * structure. This allows exposure under a different name.
114 */
其中使用了 3 个参数:要传递的参数变量名, 变量的数据类型, 以及访问参数的权限。
注：宏的第三个参数用于指定访问权限，如果为 0，该参数将不出现在 sysfs 文件系统中，允许的访问权限为 S_IRUSR，S_IWUSR，S_IRGRP，S_IWGRP，S_IROTH 和S_IWOTH 的组合，它们分别对应于用户读，用户写，用户组读，用户组写，其他用户读和其他用户写，因此用文件的访问权限设置是一致的。
而权限的设置可以参考如下：（也可以自己定义，它类似chmod中权限的使用）
权限在include/linux/stat.h中有定义：
比如：
#define S_IRWXU 00700
#define S_IRUSR 00400
#define S_IWUSR 00200
#define S_IXUSR 00100
#define S_IRWXG 00070
#define S_IRGRP 00040
#define S_IWGRP 00020
#define S_IXGRP 00010
#define S_IRWXO 00007
#define S_IROTH 00004
#define S_IWOTH 00002
#define S_IXOTH 00001
3.实例
在ubuntu 10.10下，内核版本2.26.35
/**module_param()**/
/*This is a test to learn how it work*/
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
MODULE_LICENSE("GPL");
MODULE_AUTHOR("SUZHAODA");
MODULE_DESCRIPTION("Module_param() test");
static char *who = "world";
static int times = 1;
module_param(times,int,S_IRUSR);
module_param(who,charp,S_IRUSR);
static int hello_init(void)
{
int i;
for(i = 0;i < times;i++)
printk(KERN_ALERT "(%d) hello,%s/n",i,who);
return 0;
}
static void hello_exit(void)
{
printk(KERN_ALERT "Goodbye,%s!/n",who);
}
module_init(hello_init);
module_exit(hello_exit);
4.makefile
obj-m := hello.o
KERNELBUILD := /lib/modules/$(shell uname -r)/build
default:
make -C $(KERNELBUILD) M=$(shell pwd) modules
clean:
rm -rf *.o *.ko *.mod.c .*.cmd *.markers *.order *.symvers .tmp_version
5.实现
sudo make
sudo insmod hello.ko who="world" times=5
dmesg
rmmdo hello
dmesg
