rom/exec/cause.c

   1 /*
   2     Copyright © 1995-2011, The AROS Development Team. All rights reserved.
   3     $Id$
   4
   5     Desc: Cause() - Cause a software interrupt.
   6     Lang: english
   7 */
   8
   9 #include <aros/asmcall.h>
  10 #include <exec/execbase.h>
  11 #include <hardware/intbits.h>
  12 #include <proto/kernel.h>
  13
  14 #include "chipset.h"
  15 #include "exec_intern.h"
  16
  17 /*****************************************************************************
  18
  19     NAME */
  20 #include <exec/interrupts.h>
  21 #include <proto/exec.h>
  22
  23         AROS_LH1(void, Cause,
  24
  25 /*  SYNOPSIS */
  26         AROS_LHA(struct Interrupt *, softint, A1),
  27
  28 /*  LOCATION */
  29         struct ExecBase *, SysBase, 30, Exec)
  30
  31 /*  FUNCTION
  32         Schedule a software interrupt to occur. If the processor is
  33         currently running a user task, then the software interrupt will
  34         prempt the current task and run itself. From a real interrupt, it
  35         will queue the software interrupt for a later time.
  36
  37         Software interrupts are useful from hardware interrupts if you
  38         wish to defer your processing down to a lower level. They can
  39         also be used in some special cases of device I/O. The timer.device
  40         and audio.device allow software interrupt driven timing and
  41         audio output respectively.
  42
  43         Software interrupts are restricted to 5 different priority levels,
  44         +32, +16, 0, -16, -32.
  45
  46         Software interrupts can only be scheduled once.
  47
  48         The software interrupt is called with the following prototype:
  49
  50     AROS_INTC1(YourIntCode, APTR, interruptData)
  51
  52         The interruptData is the value of the is_Data field.
  53
  54     INPUTS
  55         softint     -   The interrupt you wish to schedule. When setting up
  56                         you should set the type of the interrupt to either
  57                         NT_INTERRUPT or NT_UNKNOWN.
  58
  59     RESULT
  60         The software interrupt will be delivered, or queued for later
  61         delivery.
  62
  63     NOTES
  64         No bounds checking on the software interrupt priority is done.
  65         Passing a bad priority to the system can have a strange effect.
  66
  67     EXAMPLE
  68
  69     BUGS
  70         Older versions of the Amiga operating system require that the
  71         software interrupts preserve the A6 register.
  72
  73         Software interrupts which are added from a software interrupt of
  74         lower priority may not be called immediately.
  75
  76     SEE ALSO
  77
  78     INTERNALS
  79
  80 ******************************************************************************/
  81 {
  82     AROS_LIBFUNC_INIT
  83
  84     UBYTE pri;
  85
  86     Disable();
  87
  88     /* Check to ensure that this node is not already in a list. */
  89     if (softint->is_Node.ln_Type != NT_SOFTINT)
  90     {
  91         /* Scale the priority down to a number between 0 and 4 inclusive
  92         We can use that to index into exec's software interrupt lists. */
  93         pri = (softint->is_Node.ln_Pri + 0x20)>>4;
  94
  95         /* We are accessing an Exec list, protect ourselves. */
  96         ADDTAIL(&SysBase->SoftInts[pri].sh_List, &softint->is_Node);
  97         softint->is_Node.ln_Type = NT_SOFTINT;
  98
  99         /* Signal pending software interrupt condition */
 100         SysBase->SysFlags |= SFF_SoftInt;
 101
 102         /*
 103          * Quick soft int request. For optimal performance m68k-amiga
 104          * Enable() does not do any extra SFF_SoftInt checks
 105          */
 106         CUSTOM_CAUSE(INTF_SOFTINT);
 107         /*
 108          * If we are in usermode the software interrupt will end up being triggered
 109          * in Enable(). On Amiga hardware this happens because a hardware interrupt
 110          * was queued. On other machines Enable() will simulate this behavior,
 111          * looking at SFF_SoftInt flag.
 112          */
 113     }
 114     Enable();
 115
 116     AROS_LIBFUNC_EXIT
 117 } /* Cause() */
 118
 119 /*
 120     This is the dispatcher for software interrupts. We go through the
 121     lists and remove the interrupts before calling them. Because we
 122     can be interrupted we should not cache the next pointer, but
 123     retreive it from ExecBase each time.
 124
 125     Note: All these arguments are passed to the function, so you must
 126     at least declare all of them. You do not however have to use any
 127     of them (although that is recommended).
 128
 129     This procedure could be more efficient.
 130 */
 131
 132 AROS_INTH0(SoftIntDispatch)
 133 {
 134     AROS_INTFUNC_INIT
 135
 136     struct Interrupt *intr = NULL;
 137     BYTE i;
 138
 139     /* disable soft ints temporarily */
 140     CUSTOM_ACK(INTF_SOFTINT);
 141
 142     /* Don't bother if there are no software ints queued. */
 143     if( SysBase->SysFlags & SFF_SoftInt )
 144     {
 145         /* Clear Software interrupt pending flag. */
 146         SysBase->SysFlags &= ~(SFF_SoftInt);
 147
 148         for(;;)
 149         {
 150             for(i=4; i>=0; i--)
 151             {
 152                 /*
 153                  * This KrnCli() is needed because we could re-enter here after one handler has already
 154                  * been executed. In this case interrupts have been enabled before calling the handler.
 155                  */
 156                 KrnCli();
 157                 intr = (struct Interrupt *)RemHead(&SysBase->SoftInts[i].sh_List);
 158
 159                 if (intr)
 160                 {
 161                     intr->is_Node.ln_Type = NT_INTERRUPT;
 162
 163                     /*
 164                      * SoftInt handlers are called with interrupts enabled,
 165                      * this is how original AmigaOS(tm) works
 166                      */
 167                     KrnSti();
 168
 169                     /* Call the software interrupt. */
 170                     AROS_INTC1(intr->is_Code, intr->is_Data);
 171
 172                     /* Get out and start loop *all* over again *from scratch*! */
 173                     break;
 174                 }
 175             }
 176             if (!intr)
 177             {
 178                 /*
 179                  * We executed KrnCli() and attempted to fetch a request from the list,
 180                  * but the list was empty.
 181                  * We are going to exit, but before this we need to re-enable
 182                  * interrupts. Otherwise we exit this vector with disabled interrupts,
 183                  * screwing things up.
 184                  */
 185                 KrnSti();
 186                 break;
 187             }
 188         }
 189     }
 190
 191     /* re-enable soft ints */
 192     CUSTOM_ENABLE(INTB_SOFTINT);
 193
 194     return FALSE;
 195
 196     AROS_INTFUNC_EXIT
 197 }