moudle_param_call

//函数源码

#define module_param_call(name,set,get, arg,perm)                              \

          staticconst struct kernel_param_ops__param_ops_##name =              \

                    {.flags = 0, (void *)set, (void *)get };                    \

          __module_param_call(MODULE_PARAM_PREFIX,                     \

                                   name, &__param_ops_##name, arg,                \

                                   (perm) + sizeof(__check_old_set_param(set))*0, -1,0)

调用module_param_call会填充kernel_param中最重要的就是kernel_param_ops结构体，此结构体会被填充，此结构体包含了set函数指针和get函数指针重要的函数指针。

struct kernel_param {

          const char *name;

          const struct kernel_param_ops *ops;

          u16 perm;

          s16 level;

          union {

                    void *arg;

                    const struct kparam_string *str;

                    const struct kparam_array *arr;

          };

};

struct kernel_param_ops {

          /* How the ops should behave */

          unsigned int flags;

          /* Returns 0, or -errno.  arg is in kp->arg. */

          int (*set)(const char *val, const struct kernel_param *kp);

          /* Returns length written or -errno.  Buffer is 4k (ie. be short!) */

          int (*get)(char *buffer, const struct kernel_param *kp);

          /* Optional function to free kp->arg when module unloaded. */

          void (*free)(void *arg);

};

在__module_param_call函数中，通过__attribute__(__section(“__param”))将数据放入__param字段中，即初始化kernel_param结构体。当通过echo进行输入时，当名字匹配时，则调用set函数。

#define __module_param_call(prefix, name, ops, arg, perm, level, flags) \

     /* Default value instead of permissions? */                            \

     static const char __param_str_##name[] = prefix #name;                 \

     static struct kernel_param __moduleparam_const __param_##name          \

             __used                                                                        \

    __attribute__ ((unused,__section__ ("__param"),aligned(sizeof(void *)))) \

     = { __param_str_##name, THIS_MODULE, ops,                              \

         VERIFY_OCTAL_PERMISSIONS(perm), level, flags, { arg } }