include/sysemu/rtc.h

   1 /*
   2  * RTC configuration and clock read
   3  *
   4  * Copyright (c) 2003-2021 QEMU contributors
   5  *
   6  * Permission is hereby granted, free of charge, to any person obtaining a copy
   7  * of this software and associated documentation files (the "Software"), to deal
   8  * in the Software without restriction, including without limitation the rights
   9  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  10  * copies of the Software, and to permit persons to whom the Software is
  11  * furnished to do so, subject to the following conditions:
  12  *
  13  * The above copyright notice and this permission notice shall be included in
  14  * all copies or substantial portions of the Software.
  15  *
  16  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  17  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  18  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
  19  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  20  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  21  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  22  * THE SOFTWARE.
  23  */
  24
  25 #ifndef SYSEMU_RTC_H
  26 #define SYSEMU_RTC_H
  27
  28 /**
  29  * qemu_get_timedate: Get the current RTC time
  30  * @tm: struct tm to fill in with RTC time
  31  * @offset: offset in seconds to adjust the RTC time by before
  32  *          converting to struct tm format.
  33  *
  34  * This function fills in @tm with the current RTC time, as adjusted
  35  * by @offset (for example, if @offset is 3600 then the returned time/date
  36  * will be one hour further ahead than the current RTC time).
  37  *
  38  * The usual use is by RTC device models, which should call this function
  39  * to find the time/date value that they should return to the guest
  40  * when it reads the RTC registers.
  41  *
  42  * The behaviour of the clock whose value this function returns will
  43  * depend on the -rtc command line option passed by the user.
  44  */
  45 void qemu_get_timedate(struct tm *tm, int offset);
  46
  47 /**
  48  * qemu_timedate_diff: Return difference between a struct tm and the RTC
  49  * @tm: struct tm containing the date/time to compare against
  50  *
  51  * Returns the difference in seconds between the RTC clock time
  52  * and the date/time specified in @tm. For example, if @tm specifies
  53  * a timestamp one hour further ahead than the current RTC time
  54  * then this function will return 3600.
  55  */
  56 int qemu_timedate_diff(struct tm *tm);
  57
  58 #endif