struct ctl_table
{
        int ctl_name;                   /* Binary ID */
        const char *procname;           /* Text ID for /proc/sys, or zero */
        void *data;
        int maxlen;
        mode_t mode;
        struct ctl_table *child;
        struct ctl_table *parent;       /* Automatically set */
        proc_handler *proc_handler;     /* Callback for text formatting */
        ctl_handler *strategy;          /* Callback function for all r/w */
        void *extra1;
        void *extra2;
};


example:

        {
                .ctl_name       = KERN_PRINTK_RATELIMIT,
                .procname       = "printk_ratelimit",
                .data           = &printk_ratelimit_jiffies,
                .maxlen         = sizeof(int),
                .mode           = 0644,
                .proc_handler   = &proc_dointvec_jiffies,
                .strategy       = &sysctl_jiffies,
        },