GB Video: Implement MLT_REQ controller iterating

include/mgba/internal/gb/gb.h

@@ -62,7 +62,7 @@ enum GBSGBCommand {
 	SGB_PICON_EN,
 	SGB_DATA_SND,
 	SGB_DATA_TRN,
-	SGB_MLT_REG,
+	SGB_MLT_REQ,
 	SGB_JUMP,
 	SGB_CHR_TRN,
 	SGB_PCT_TRN,
@@ -107,6 +107,8 @@ struct GB {
 	int sgbBit;
 	int currentSgbBits;
 	uint8_t sgbPacket[16];
+	uint8_t sgbControllers;
+	uint8_t sgbCurrentController;
 
 	struct mCoreCallbacksList coreCallbacks;
 	struct mAVStream* stream;

include/mgba/internal/gb/serialize.h

@@ -258,7 +258,9 @@ DECL_BITS(GBSerializedMemoryFlags, ActiveRtcReg, 5, 3);
 DECL_BITFIELD(GBSerializedSGBFlags, uint32_t);
 DECL_BITS(GBSerializedSGBFlags, P1Bits, 0, 2);
 DECL_BITS(GBSerializedSGBFlags, RenderMode, 2, 2);
-DECL_BITS(GBSerializedSGBFlags, BufferIndex, 4, 3)
+DECL_BITS(GBSerializedSGBFlags, BufferIndex, 4, 3);
+DECL_BITS(GBSerializedSGBFlags, CurrentController, 7, 2);
+DECL_BITS(GBSerializedSGBFlags, ReqControllers, 9, 2);
 
 #pragma pack(push, 1)
 struct GBSerializedState {

src/gb/gb.c

@@ -446,6 +446,8 @@ void GBReset(struct LR35902Core* cpu) {
 	}
 
 	gb->sgbBit = -1;
+	gb->sgbControllers = 0;
+	gb->sgbCurrentController = 0;
 	gb->currentSgbBits = 0;
 	memset(gb->sgbPacket, 0, sizeof(gb->sgbPacket));
 

src/gb/io.c

@@ -113,6 +113,9 @@ static void _writeSGBBits(struct GB* gb, int bits) {
 		return;
 	}
 	gb->currentSgbBits = bits;
+	if (bits == 3) {
+		gb->sgbCurrentController = (gb->sgbCurrentController + 1) & gb->sgbControllers;
+	}
 	if (gb->sgbBit == 128 && bits == 2) {
 		GBVideoWriteSGBPacket(&gb->video, gb->sgbPacket);
 		++gb->sgbBit;
@@ -503,10 +506,13 @@ void GBIOWrite(struct GB* gb, unsigned address, uint8_t value) {
 
 static uint8_t _readKeys(struct GB* gb) {
 	uint8_t keys = *gb->keySource;
+	if (gb->sgbCurrentController != 0) {
+		keys = 0;
+	}
 	switch (gb->memory.io[REG_JOYP] & 0x30) {
 	case 0x30:
 	// TODO: Increment
-		keys = (gb->video.sgbCommandHeader >> 3) == SGB_MLT_REG ? 0xF : 0;
+		keys = (gb->video.sgbCommandHeader >> 3) == SGB_MLT_REQ ? 0xF - gb->sgbCurrentController : 0;
 		break;
 	case 0x20:
 		keys >>= 4;

src/gb/serialize.c

@@ -213,6 +213,8 @@ void GBSGBSerialize(struct GB* gb, struct GBSerializedState* state) {
 	flags = GBSerializedSGBFlagsSetP1Bits(flags, gb->currentSgbBits);
 	flags = GBSerializedSGBFlagsSetRenderMode(flags, gb->video.renderer->sgbRenderMode);
 	flags = GBSerializedSGBFlagsSetBufferIndex(flags, gb->video.sgbBufferIndex);
+	flags = GBSerializedSGBFlagsSetReqControllers(flags, gb->sgbControllers);
+	flags = GBSerializedSGBFlagsSetCurrentController(flags, gb->sgbCurrentController);
 	STORE_32LE(flags, 0, &state->sgb.flags);
 
 	memcpy(state->sgb.packet, gb->video.sgbPacketBuffer, sizeof(state->sgb.packet));
@@ -244,6 +246,8 @@ void GBSGBDeserialize(struct GB* gb, const struct GBSerializedState* state) {
 	gb->currentSgbBits = GBSerializedSGBFlagsGetP1Bits(flags);
 	gb->video.renderer->sgbRenderMode = GBSerializedSGBFlagsGetRenderMode(flags);
 	gb->video.sgbBufferIndex = GBSerializedSGBFlagsGetBufferIndex(flags);
+	gb->sgbControllers = GBSerializedSGBFlagsGetReqControllers(flags);
+	gb->sgbCurrentController = GBSerializedSGBFlagsGetCurrentController(flags);
 
 	memcpy(gb->video.sgbPacketBuffer, state->sgb.packet, sizeof(state->sgb.packet));
 	memcpy(gb->sgbPacket, state->sgb.inProgressPacket, sizeof(state->sgb.inProgressPacket));

src/gb/video.c

@@ -701,7 +701,8 @@ void GBVideoWriteSGBPacket(struct GBVideo* video, uint8_t* data) {
 	case SGB_ATTR_TRN:
 	case SGB_ATTR_SET:
 		break;
-	case SGB_MLT_REG:
+	case SGB_MLT_REQ:
+		video->p->sgbControllers = video->sgbPacketBuffer[1] & 0x3;
 		return;
 	case SGB_MASK_EN:
 		video->renderer->sgbRenderMode = video->sgbPacketBuffer[1] & 0x3;