From 7750ab47c06aaaaee6894a403ddeae2baa8eb169 Mon Sep 17 00:00:00 2001
From: RocketRobz <bobesh8@gmail.com>
Date: Sat, 9 Oct 2021 19:39:39 -0600
Subject: [PATCH] Detect 3DS console without reading NAND

---
 arm7/source/main.c   |  6 ++++++
 arm9/source/main.cpp |  1 +
 arm9/source/nandio.c | 14 ++++++--------
 3 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/arm7/source/main.c b/arm7/source/main.c
index 5cce55e..cc3e85c 100644
--- a/arm7/source/main.c
+++ b/arm7/source/main.c
@@ -123,6 +123,12 @@ int main() {
 
 	setPowerButtonCB(powerButtonCB);
 
+	// Check for 3DS
+	u8 byteBak = i2cReadRegister(0x4A, 0x71);
+	i2cWriteRegister(0x4A, 0x71, 0xD2);
+	fifoSendValue32(FIFO_USER_05, i2cReadRegister(0x4A, 0x71));
+	i2cWriteRegister(0x4A, 0x71, byteBak);
+
 	if (isDSiMode() /*|| ((REG_SCFG_EXT & BIT(17)) && (REG_SCFG_EXT & BIT(18)))*/) {
 		/*for (int i = 0; i < 8; i++) {
 			*(u8*)(0x2FFFD00+i) = *(u8*)(0x4004D07-i);	// Get ConsoleID
diff --git a/arm9/source/main.cpp b/arm9/source/main.cpp
index d479634..7dc288c 100644
--- a/arm9/source/main.cpp
+++ b/arm9/source/main.cpp
@@ -154,6 +154,7 @@ int main(int argc, char **argv) {
 		*(vu32*)(0x0DFFFE0C) = 0x474D3969;		// Check for 32MB of RAM
 		if (*(vu32*)(0x0DFFFE0C) == 0x474D3969) {
 			ramdrive2Mount();
+			is3DS = fifoGetValue32(FIFO_USER_05) != 0xD2;
 		}
 		if (!(keysHeld() & KEY_X)) {
 			nandMounted = nandMount();
diff --git a/arm9/source/nandio.c b/arm9/source/nandio.c
index 6f0d6bf..b9f61c0 100644
--- a/arm9/source/nandio.c
+++ b/arm9/source/nandio.c
@@ -11,8 +11,6 @@
 //#define SECTOR_SIZE 512
 #define CRYPT_BUF_LEN 64
 
-extern bool is3DS;
-
 extern bool nand_Startup();
 
 static u8* crypt_buf = 0;
@@ -49,11 +47,11 @@ bool nandio_startup() {
 	if (!nand_Startup()) return false;
 
 	nand_ReadSectors(0, 1, sector_buf);
-	is3DS = parse_ncsd(sector_buf, 0) == 0;
-	//if (is3DS) return false;
+	bool isDSi = parse_ncsd(sector_buf, 0) != 0;
+	//if (!isDSi) return false;
 
 	if (*(u32*)(0x2FFD7BC) == 0) {
-		if (is3DS) {
+		if (!isDSi) {
 			FILE* cidFile = fopen("sd:/gm9/out/nand_cid.mem", "rb");
 			if (!cidFile) return false;
 			fread((void*)0x2FFD7BC, 1, 16, cidFile);
@@ -75,12 +73,12 @@ bool nandio_startup() {
 	}
 
 	// iprintf("sector 0 is %s\n", is3DS ? "3DS" : "DSi");
-	dsi_crypt_init((const u8*)consoleIDfixed, (const u8*)0x2FFD7BC, is3DS);
+	dsi_crypt_init((const u8*)consoleIDfixed, (const u8*)0x2FFD7BC, !isDSi);
 	dsi_nand_crypt(sector_buf, sector_buf, 0, SECTOR_SIZE / AES_BLOCK_SIZE);
-	parse_mbr(sector_buf, is3DS, 0);
+	parse_mbr(sector_buf, !isDSi, 0);
 
 	mbr_t *mbr = (mbr_t*)sector_buf;
-	nandio_set_fat_sig_fix(is3DS ? 0 : mbr->partitions[0].offset);
+	nandio_set_fat_sig_fix(isDSi ? mbr->partitions[0].offset : 0);
 
 	if (crypt_buf == 0) {
 		crypt_buf = (u8*)memalign(32, SECTOR_SIZE * CRYPT_BUF_LEN);