直接从CMOS读取系统时间

following code come from Linux Kernel 0.01

#define CMOS_READ(addr) ({ /
outb_p(0x80|addr,0x70); /
inb_p(0x71); /
})

#define BCD_TO_BIN(val) ((val)=((val)&15) + ((val)>>4)*10)

static void time_init(void)
{
    struct tm time;

    do {
        time.tm_sec = CMOS_READ(0);
        time.tm_min = CMOS_READ(2);
        time.tm_hour = CMOS_READ(4);
        time.tm_mday = CMOS_READ(7);
        time.tm_mon = CMOS_READ(8)-1;
        time.tm_year = CMOS_READ(9);
    } while (time.tm_sec != CMOS_READ(0));
    BCD_TO_BIN(time.tm_sec);
    BCD_TO_BIN(time.tm_min);
    BCD_TO_BIN(time.tm_hour);
    BCD_TO_BIN(time.tm_mday);
    BCD_TO_BIN(time.tm_mon);
    BCD_TO_BIN(time.tm_year);
    startup_time = kernel_mktime(&time);
}