rom/timer/beginio.c

   1 /*
   2     Copyright © 1995-2011, The AROS Development Team. All rights reserved.
   3     $Id$
   4
   5     Desc: BeginIO - Start up a timer.device request, generic version for software timer emulation
   6     Lang: english
   7 */
   8
   9 #include <aros/libcall.h>
  10
  11 #include "timer_intern.h"
  12
  13 /*****************************************************************************
  14
  15     NAME */
  16 #include <devices/timer.h>
  17 #include <proto/timer.h>
  18         AROS_LH1(void, BeginIO,
  19
  20 /*  SYNOPSIS */
  21         AROS_LHA(struct timerequest *, timereq, A1),
  22
  23 /*  LOCATION */
  24         struct TimerBase *, TimerBase, 5, Timer)
  25
  26 /*  FUNCTION
  27         BeginIO() will perform a timer.device command. It is normally
  28         called from within DoIO() and SendIO().
  29
  30     INPUT
  31         timereq         - The request to process.
  32
  33     RESULT
  34         The requested message will be processed.
  35
  36     NOTES
  37         This function is safe to call from interrupts.
  38
  39     EXAMPLE
  40
  41     BUGS
  42
  43     SEE ALSO
  44         exec.library/AbortIO(), exec.library/SendIO(), exec.library/DoIO()
  45
  46     INTERNALS
  47
  48     HISTORY
  49         23-01-1998  iaint       Implemented again.
  50
  51 ******************************************************************************/
  52
  53 {
  54     AROS_LIBFUNC_INIT
  55
  56     /*
  57      * common_BeginIO() is called in the middle of BeginIO() implementation
  58      * to provide support for time base correction.
  59      * If we query TBC hardware before starting doing anything here, we can
  60      * calculate how much time it took to do all processing and take this
  61      * into account when programming hardware.
  62      * See PowerPC native versions for working example.
  63      */
  64
  65     common_BeginIO(timereq, TimerBase);
  66
  67     /*
  68      * common_BeginIO() returns TRUE if it wants us to re-adjust
  69      * our hardware (if the request was added to the head of a queue
  70      * and elapsed time changes).
  71      * Real hardware version of timer.device needs to do this here.
  72      */
  73
  74     AROS_LIBFUNC_EXIT
  75 }