CONFIG_RTC_SYSTOHC

来源：互联网发布：电音软件编辑：程序博客网时间：2024/06/06 01:45

kernel中如果定义CONFIG_RTC_SYSTOHC，则会编译systohc.c
obj-$(CONFIG_RTC_SYSTOHC)   += systohc.o
systohc.c 中只有一个函数，会在kernel 初始化的后期自动执行late_initcall(rtc_hctosys);
static int __init rtc_hctosys(void)
{
   int err = -ENODEV;
   struct rtc_time tm;
   struct timespec64 tv64 = {
       .tv_nsec = NSEC_PER_SEC >> 1,
   };
   struct rtc_device *rtc = rtc_class_open(CONFIG_RTC_HCTOSYS_DEVICE);

   if (rtc == NULL) {
       pr_info("unable to open rtc device (%s)\n",
           CONFIG_RTC_HCTOSYS_DEVICE);
       goto err_open;
   }

   err = rtc_read_time(rtc, &tm);
   if (err) {
       dev_err(rtc->dev.parent,
           "hctosys: unable to read the hardware clock\n");
       goto err_read;

   }

   tv64.tv_sec = rtc_tm_to_time64(&tm);

   err = do_settimeofday64(&tv64);

   dev_info(rtc->dev.parent,
       "setting system clock to "
       "%d-%02d-%02d %02d:%02d:%02d UTC (%lld)\n",
       tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday,
       tm.tm_hour, tm.tm_min, tm.tm_sec,
       (long long) tv64.tv_sec);

err_read:
   rtc_class_close(rtc);

err_open:
   rtc_hctosys_ret = err;

   return err;
}
这个函数最主要的作用是打开rtc driver，rtc_class_open(CONFIG_RTC_HCTOSYS_DEVICE);
读取时间
rtc_read_time(rtc, &tm);
将时间写到kernel中
err = do_settimeofday64(&tv64);
最后会输出log
rtc-efi rtc-efi: setting system clock to 2016-11-24 06:48:02 UTC (1479970082)

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