日期:2014-05-16 浏览次数:20962 次
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.sourceforge.jp/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: