rom/graphics/qblit.c

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