Merge pull request #3985 from finalpatch/lf/idle

Support DPMI idle (INT 2FH Function 1680H) and DOS idle (INT 28H)

include/callback.h

@@ -27,7 +27,7 @@ extern CallBack_Handler CallBack_Handlers[];
 
 enum { CB_RETN,CB_RETF,CB_RETF8,CB_IRET,CB_IRETD,CB_IRET_STI,CB_IRET_EOI_PIC1,
 		CB_IRQ0,CB_IRQ1,CB_IRQ1_BREAK,CB_IRQ9,CB_IRQ12,CB_IRQ12_RET,CB_MOUSE,
-		/*CB_INT28,*/CB_INT29,CB_INT16,CB_HOOKABLE,CB_TDE_IRET,CB_IPXESR,CB_IPXESR_RET,
+		CB_INT28,CB_INT29,CB_INT16,CB_HOOKABLE,CB_TDE_IRET,CB_IPXESR,CB_IPXESR_RET,
 		CB_INT21,CB_INT13,CB_VESA_WAIT,CB_VESA_PM,CB_IRET_EOI_PIC2,CB_CPM,
         CB_RETF_STI,CB_RETF_CLI,CB_INT6F_ATOK};
 

src/cpu/callback.cpp

@@ -569,11 +569,11 @@ Bitu CALLBACK_SetupExtra(Bitu callback, Bitu type, PhysPt physAddress, bool use_
 		for (uint8_t i=0;i<=0x0b;i++) phys_writeb(physAddress+0x02+i,0x90);
 		phys_writew(physAddress+0x0e,(uint16_t)0xedeb);	//jmp callback
 		return (use_cb?0x10:0x0c);
-	/*case CB_INT28:	// DOS idle
+	case CB_INT28:	// DOS idle
 		phys_writeb(physAddress+0x00,(uint8_t)0xFB);		// STI
 		phys_writeb(physAddress+0x01,(uint8_t)0xF4);		// HLT
 		phys_writeb(physAddress+0x02,(uint8_t)0xcf);		// An IRET Instruction
-		return (0x04);*/
+		return (0x04);
 	case CB_INT29:	// fast console output
         if (IS_PC98_ARCH) LOG_MSG("WARNING: CB_INT29 callback setup not appropriate for PC-98 mode (INT 10h no longer BIOS call)");
 		if (use_cb) {

src/dos/dev_con.h

@@ -721,7 +721,29 @@ bool device_CON::Read(uint8_t * data,uint16_t * size) {
             continue;
         }
 
-		reg_ah=(IS_EGAVGA_ARCH)?0x10:0x0;
+        const uint8_t int16_poll_function=(IS_EGAVGA_ARCH)?0x11:0x1;
+        const uint8_t int16_read_function=(IS_EGAVGA_ARCH)?0x10:0x0;
+
+        static const bool idle_enabled = ((Section_prop*)control->GetSection("dos"))->Get_bool("dos idle api");
+        if (idle_enabled) {
+            // Poll the keyboard until there is a key-press ready to read. If there
+            // is no input (ZF=0) then call INT 28h to release the rest of our
+            // timeslice to host system.
+            while (true) {
+                reg_ah=int16_poll_function;
+                if (IS_PC98_ARCH)
+                    INT16_Handler_Wrap();
+                else
+                    CALLBACK_RunRealInt(0x16);
+                if (GETFLAG(ZF) == 0) {
+                    break;
+                } else {
+                    CALLBACK_RunRealInt(0x28);
+                }
+            }
+        }
+
+		reg_ah=int16_read_function;
 
         /* FIXME: PC-98 emulation should eventually use CONIO emulation that
          *        better emulates the actual platform. The purpose of this

src/dos/dos.cpp

@@ -4262,7 +4262,11 @@ public:
 		callback[4].Install(DOS_27Handler,CB_IRET,"DOS Int 27");
 		callback[4].Set_RealVec(0x27);
 
-		callback[5].Install(NULL,CB_IRET/*CB_INT28*/,"DOS idle");
+        if (section->Get_bool("dos idle api")) {
+            callback[5].Install(NULL,CB_INT28,"DOS idle");
+        } else {
+            callback[5].Install(NULL,CB_IRET,"DOS idle");
+        }
 		callback[5].Set_RealVec(0x28);
 
 		if (IS_PC98_ARCH) {

src/dos/dos_misc.cpp

@@ -25,6 +25,7 @@
 #include "dos_inc.h"
 #include "control.h"
 #include "support.h"
+#include "cpu.h"
 
 #include <array>
 #include <cstring>
@@ -396,8 +397,15 @@ static bool DOS_MultiplexFunctions(void) {
 		return false;
 	}
 	case 0x1680:	/*  RELEASE CURRENT VIRTUAL MACHINE TIME-SLICE */
-		//TODO Maybe do some idling but could screw up other systems :)
-		return true; //So no warning in the debugger anymore
+    {
+        static const bool idle_enabled = ((Section_prop*)control->GetSection("dos"))->Get_bool("dos idle api");
+        if (idle_enabled) {
+            CPU_STI();
+            CPU_HLT(reg_eip);
+            reg_al = 0;
+        }
+		return true;
+    }
 	case 0x1689:	/*  Kernel IDLE CALL */
 	case 0x168f:	/*  Close awareness crap */
 	   /* Removing warning */

src/dosbox.cpp

@@ -4503,6 +4503,10 @@ void DOSBOX_SetupConfigSections(void) {
     Pbool->Set_help("If set, DOS APIs for communications with the Windows clipboard will be enabled for shared clipboard communications.");
     Pbool->SetBasic(true);
 
+    Pbool = secprop->Add_bool("dos idle api",Property::Changeable::OnlyAtStart,true);
+    Pbool->Set_help("If set, DOSBox-X can lower the host system's CPU load when a supported guest program is idle.");
+    Pbool->SetBasic(true);
+
     secprop=control->AddSection_prop("ipx",&Null_Init,true);
     Pbool = secprop->Add_bool("ipx",Property::Changeable::WhenIdle, false);
     Pbool->Set_help("Enable ipx over UDP/IP emulation.");