rom/graphics/qbsblit.c

   1 /*
   2     Copyright © 1995-2001, The AROS Development Team. All rights reserved.
   3     $Id$
   4
   5     Desc: Queue a beam-synchronized Blit
   6     Lang: english
   7 */
   8
   9 #include <proto/exec.h>
  10 #include <hardware/intbits.h>
  11 #include <hardware/blit.h>
  12 #include <graphics/gfxbase.h>
  13
  14 #include "graphics_intern.h"
  15
  16 /*****************************************************************************
  17
  18     NAME */
  19 #include <proto/graphics.h>
  20
  21         AROS_LH1(void, QBSBlit,
  22
  23 /*  SYNOPSIS */
  24         AROS_LHA(struct bltnode *, bn, A1),
  25
  26 /*  LOCATION */
  27         struct GfxBase *, GfxBase, 49, Graphics)
  28
  29 /*  FUNCTION
  30         Queues a request for a beam-synchronized  blit.
  31
  32     INPUTS
  33         bn - pointer to blitnode structure
  34
  35     RESULT
  36         The routine that function in the bltnode is pointing to is
  37         called when the blitter is ready for work. No other task will
  38         be able to access the blitter while you're doing the blit.
  39         Queued blits have precedence over a task that tries to own the
  40         blitter via OwnBlitter(). So all queued blitter requests will
  41         be done first until the task that attempts a OwnBlitter can
  42         actually access the blitter.
  43
  44     NOTES
  45         Not all hardware has a blitter. On hardware where there is no
  46         blitter, a blitter is simulated. Therefore all code that will
  47         be executed in the function that is called must not contain
  48         code that is hacking the blitter's register but should contain
  49         calls to graphics functions instead.
  50
  51     EXAMPLE
  52
  53     BUGS
  54
  55     SEE ALSO
  56         QBSBlit(), OwnBlitter(), DisownBlitter(), hardware/blit.h
  57
  58     INTERNALS
  59
  60     HISTORY
  61
  62 ******************************************************************************/
  63 {
  64   AROS_LIBFUNC_INIT
  65
  66   /* this function uses the queue bsblthd (bsblttl) */
  67
  68   /* I am accessing a public structure and there's no semaphore...*/
  69   Disable();
  70
  71   if (NULL == GfxBase->bsblthd)
  72   {
  73     /* OwnBlitter() only if both lists are empty */
  74     if (NULL == GfxBase->blthd)
  75       OwnBlitter();
  76
  77     /* it's the first one in the list */
  78     GfxBase->bsblthd = bn;
  79     GfxBase->bsblttl = bn;
  80
  81     /* In this case the following also has to happen:
  82        It is my understanding that at the end of every blit an interrupt
  83        occurs that can take care of any blits in this queue or allow
  84        a taks to wake up when it was blocked due to a call to OwnBlitter.
  85        But in this case there might not be such an interrupt for a long
  86        time if no calls to blitterfunctions are made. Therefore this
  87        blit might be queued forever. To avoid this I have to cause
  88        a Blitter interrupt, if no task owns the blitter right now.
  89        (BlitOwner)
  90     */
  91     /*
  92       !!! missing code here!! See explanation above!
  93     */
  94 #if (AROS_FLAVOUR & AROS_FLAVOUR_BINCOMPAT) && defined(mc68000)
  95     {
  96       /* Trigger blitter interrupt */
  97       volatile struct Custom *custom = (struct Custom *)(void **)0xdff000;
  98       custom->intreq = INTF_SETCLR | INTF_BLIT;
  99       custom->intena = INTF_SETCLR | INTF_BLIT;
 100     }
 101 #endif
 102   }
 103   else
 104   {
 105     /* queue it at the end */
 106     GfxBase->bsblttl->n = bn;
 107     GfxBase->bsblttl    = bn;
 108   }
 109
 110   Enable();
 111
 112   AROS_LIBFUNC_EXIT
 113
 114 } /* QBSBlit */