typedef struct {
    ril_cmd_id_t cmd_id;    /**< A unique ID  */
    ril_request_mode_t mode;    /**< AT command mode, */
    ril_result_code_t res_code;    /**< Final response code */
    void *cmd_param;    /**< A pointer to the subparameter structure, user should cast it to the right data structure specified for each command. */
    char *test_mode_str;    /**< A pointer to the response string  */
    uint32_t test_mode_str_len;    /**< The response string  */
} ril_cmd_response_t;

typedef int (*ril_cmd_response_callback_t)(ril_cmd_response_t *response);

extern  ril_status_t   ril_request_query_network_state(ril_request_mode_t mode,
        int32_t display_mode,
        ril_cmd_response_callback_t callback,
        void *user_data);

    问题：1，我知道代码中ril_cmd_response_t是结构体，但是 typedef int (*ril_cmd_response_callback_t)(ril_cmd_response_t *response);又是什么？
          2，如何读取 ril_cmd_response_callback_t定义的callback变量中的结构体成员？
          3，谢谢

谢谢！