GB MBC: Support for unlicensed Wisdom Tree Game Boy mapper

CHANGES

@@ -17,6 +17,7 @@ Features:
  - Ports: Ability to crop SGB borders off screen (closes mgba.io/i/1204)
  - Cheats: Add support for loading Libretro-style cht files
  - GBA Cheats: Add support for loading EZ Flash-style cht files
+ - Support for unlicensed Wisdom Tree Game Boy mapper
 Emulation fixes:
  - GBA: All IRQs have 7 cycle delay (fixes mgba.io/i/539, mgba.io/i/1208)
  - GBA: Reset now reloads multiboot ROMs

README.md

@@ -49,6 +49,7 @@ The following mappers are fully supported:
 - MBC5
 - MBC5+Rumble
 - MBC7
+- Wisdom Tree (unlicensed)
 
 The following mappers are partially supported:
 

include/mgba/gb/interface.h

@@ -34,6 +34,7 @@ enum GBMemoryBankControllerType {
 	GB_HuC3 = 0x12,
 	GB_POCKETCAM = 0x13,
 	GB_TAMA5 = 0x14,
+	GB_UNL_WISDOM_TREE = 0x20,
 	GB_MBC3_RTC = 0x103,
 	GB_MBC5_RUMBLE = 0x105
 };

src/gb/mbc.c

@@ -35,6 +35,7 @@ static void _GBHuC1(struct GB*, uint16_t address, uint8_t value);
 static void _GBHuC3(struct GB*, uint16_t address, uint8_t value);
 static void _GBPocketCam(struct GB* gb, uint16_t address, uint8_t value);
 static void _GBTAMA5(struct GB* gb, uint16_t address, uint8_t value);
+static void _GBWisdomTree(struct GB* gb, uint16_t address, uint8_t value);
 
 static uint8_t _GBMBC2Read(struct GBMemory*, uint16_t address);
 static uint8_t _GBMBC6Read(struct GBMemory*, uint16_t address);
@@ -119,6 +120,24 @@ static bool _isMulticart(const uint8_t* mem) {
 	return success;
 }
 
+static bool _isWisdomTree(const uint8_t* mem) {
+	int i;
+	for (i = 0x134; i < 0x14C; i += 4) {
+		if (*(uint32_t*) &mem[i] != 0) {
+			return false;
+		}
+	}
+	for (i = 0xF0; i < 0x100; i += 4) {
+		if (*(uint32_t*) &mem[i] != 0) {
+			return false;
+		}
+	}
+	if (mem[0x14D] != 0xE7) {
+		return false;
+	}
+	return true;
+}
+
 void GBMBCSwitchSramBank(struct GB* gb, int bank) {
 	size_t bankStart = bank * GB_SIZE_EXTERNAL_RAM;
 	if (bankStart + GB_SIZE_EXTERNAL_RAM > gb->sramSize) {
@@ -180,6 +199,11 @@ void GBMBCInit(struct GB* gb) {
 		if (gb->memory.mbcType == GB_MBC_AUTODETECT) {
 			switch (cart->type) {
 			case 0:
+				if (_isWisdomTree(gb->memory.rom)) {
+					gb->memory.mbcType = GB_UNL_WISDOM_TREE;
+					break;
+				}
+				// Fall through
 			case 8:
 			case 9:
 				gb->memory.mbcType = GB_MBC_NONE;
@@ -310,6 +334,9 @@ void GBMBCInit(struct GB* gb) {
 			gb->memory.cam->startRequestImage(gb->memory.cam, GBCAM_WIDTH, GBCAM_HEIGHT, mCOLOR_ANY);
 		}
 		break;
+	case GB_UNL_WISDOM_TREE:
+		gb->memory.mbcWrite = _GBWisdomTree;
+		break;
 	}
 
 	gb->memory.currentBank = 1;
@@ -1167,6 +1194,21 @@ uint8_t _GBTAMA5Read(struct GBMemory* memory, uint16_t address) {
 	}
 }
 
+void _GBWisdomTree(struct GB* gb, uint16_t address, uint8_t value) {
+	UNUSED(value);
+	int bank = address & 0x3F;
+	switch (address >> 14) {
+	case 0x0:
+		GBMBCSwitchBank0(gb, bank * 2);
+		GBMBCSwitchBank(gb, bank * 2 + 1);
+		break;
+	default:
+		// TODO
+		mLOG(GB_MBC, STUB, "Wisdom Tree unknown address: %04X:%02X", address, value);
+		break;
+	}
+}
+
 void GBMBCRTCRead(struct GB* gb) {
 	struct GBMBCRTCSaveBuffer rtcBuffer;
 	struct VFile* vf = gb->sramVf;