xref: /openbmc/qemu/include/sysemu/rtc.h (revision 05caa062)
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, time_t 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 time_t qemu_timedate_diff(struct tm *tm);
57 
58 #endif
59