com32/lib/sys/idle.c

   1 /* ----------------------------------------------------------------------- *
   2  *
   3  *   Copyright 2005 H. Peter Anvin - All Rights Reserved
   4  *
   5  *   Permission is hereby granted, free of charge, to any person
   6  *   obtaining a copy of this software and associated documentation
   7  *   files (the "Software"), to deal in the Software without
   8  *   restriction, including without limitation the rights to use,
   9  *   copy, modify, merge, publish, distribute, sublicense, and/or
  10  *   sell copies of the Software, and to permit persons to whom
  11  *   the Software is furnished to do so, subject to the following
  12  *   conditions:
  13  *
  14  *   The above copyright notice and this permission notice shall
  15  *   be included in all copies or substantial portions of the Software.
  16  *
  17  *   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  18  *   EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
  19  *   OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  20  *   NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
  21  *   HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
  22  *   WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  23  *   FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
  24  *   OTHER DEALINGS IN THE SOFTWARE.
  25  *
  26  * ----------------------------------------------------------------------- */
  27
  28 /*
  29  * idle.c
  30  *
  31  * What to do in a busy loop...
  32  */
  33
  34 #include <syslinux.h>
  35 #include <stddef.h>
  36 #include <com32.h>
  37 #include <sys/cpu.h>
  38
  39 void syslinux_idle(void)
  40 {
  41   static int do_idle = 1;
  42   static const com32sys_t sys_idle = {
  43     .eax.l = 0x0013,
  44   };
  45   com32sys_t idle_result;
  46
  47   /* This call isn't supported on SYSLINUX < 3.08, but all it does
  48      is return an error, so we don't care. */
  49
  50   if ( do_idle ) {
  51     __intcall(0x22, &sys_idle, &idle_result);
  52
  53     do_idle = ~idle_result.eflags.l & EFLAGS_CF;
  54   }
  55
  56   cpu_relax();
  57 }