time/set_system_time.c

   1 /*
   2  * (C)2012 Michael Duane Rice All rights reserved.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions are
   6  * met:
   7  *
   8  * Redistributions of source code must retain the above copyright notice, this
   9  * list of conditions and the following disclaimer. Redistributions in binary
  10  * form must reproduce the above copyright notice, this list of conditions
  11  * and the following disclaimer in the documentation and/or other materials
  12  * provided with the distribution. Neither the name of the copyright holders
  13  * nor the names of contributors may be used to endorse or promote products
  14  * derived from this software without specific prior written permission.
  15  *
  16  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  17  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  18  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  19  * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
  20  * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  21  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  22  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  23  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  24  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  25  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  26  * POSSIBILITY OF SUCH DAMAGE.
  27  */
  28
  29 /* $Id: set_system_time.c 2356 2013-04-21 16:20:01Z swfltek $ */
  30
  31 /*
  32  * Set the system time. The values passed are assumed to represent local
  33  * standard time, such as would be obtained from the typical Real Time Clock
  34  * integrated circuit. It is necessary for this to be atomic, as the value may be
  35  * incremented at interrupt time.
  36  */
  37
  38 #include <time.h>
  39 extern volatile time_t __system_time;
  40
  41 void
  42 set_system_time(time_t timestamp)
  43 {
  44
  45         asm             volatile(
  46                                            "in __tmp_reg__, __SREG__" "\n\t"
  47                                                  "cli" "\n\t"
  48                                  ::
  49         );
  50         __system_time = timestamp;
  51         asm             volatile(
  52                                           "out __SREG__, __tmp_reg__" "\n\t"
  53                                  ::
  54         );
  55 }