LXR linux/drivers/rtc/systohc.c

   1/*
   2 * This program is free software; you can redistribute it and/or modify it
   3 * under the terms of the GNU General Public License version 2 as published by
   4 * the Free Software Foundation.
   5 *
   6 */
   7#include <linux/rtc.h>
   8#include <linux/time.h>
   9
  10/**
  11 * rtc_set_ntp_time - Save NTP synchronized time to the RTC
  12 * @now: Current time of day
  13 * @target_nsec: pointer for desired now->tv_nsec value
  14 *
  15 * Replacement for the NTP platform function update_persistent_clock64
  16 * that stores time for later retrieval by rtc_hctosys.
  17 *
  18 * Returns 0 on successful RTC update, -ENODEV if a RTC update is not
  19 * possible at all, and various other -errno for specific temporary failure
  20 * cases.
  21 *
  22 * -EPROTO is returned if now.tv_nsec is not close enough to *target_nsec.
  23 *
  24 * If temporary failure is indicated the caller should try again 'soon'
  25 */
  26int rtc_set_ntp_time(struct timespec64 now, unsigned long *target_nsec)
  27{
  28        struct rtc_device *rtc;
  29        struct rtc_time tm;
  30        struct timespec64 to_set;
  31        int err = -ENODEV;
  32        bool ok;
  33
  34        rtc = rtc_class_open(CONFIG_RTC_SYSTOHC_DEVICE);
  35        if (!rtc)
  36                goto out_err;
  37
  38        if (!rtc->ops || (!rtc->ops->set_time && !rtc->ops->set_mmss64 &&
  39                          !rtc->ops->set_mmss))
  40                goto out_close;
  41
  42        /* Compute the value of tv_nsec we require the caller to supply in
  43         * now.tv_nsec.  This is the value such that (now +
  44         * set_offset_nsec).tv_nsec == 0.
  45         */
  46        set_normalized_timespec64(&to_set, 0, -rtc->set_offset_nsec);
  47        *target_nsec = to_set.tv_nsec;
  48
  49        /* The ntp code must call this with the correct value in tv_nsec, if
  50         * it does not we update target_nsec and return EPROTO to make the ntp
  51         * code try again later.
  52         */
  53        ok = rtc_tv_nsec_ok(rtc->set_offset_nsec, &to_set, &now);
  54        if (!ok) {
  55                err = -EPROTO;
  56                goto out_close;
  57        }
  58
  59        rtc_time64_to_tm(to_set.tv_sec, &tm);
  60
  61        /* rtc_hctosys exclusively uses UTC, so we call set_time here, not
  62         * set_mmss.
  63         */
  64        err = rtc_set_time(rtc, &tm);
  65
  66out_close:
  67        rtc_class_close(rtc);
  68out_err:
  69        return err;
  70}
  71