Instead of flash0directory, have a NAND subdirectory under PSP, where you can keep flash0, flash1 etc.

Also make it configurable via command line.

Core/CmdLine.cpp

@@ -512,7 +512,6 @@ void CommandLineOptions::ApplyToConfig() const {
 	if (pauseMenuExit.has_value()) {
 		g_Config.bPauseMenuExitsEmulator = pauseMenuExit.value();
 	}
-
 	if (debuggerPort.has_value()) {
 		g_Config.iRemoteISOPort = debuggerPort.value();
 		g_Config.DoNotSaveSetting(&g_Config.iRemoteISOPort);
@@ -551,6 +550,12 @@ void CommandLineOptions::ApplyToConfig() const {
 		CreateSysDirectories();
 	}
 
+	if (nand.has_value()) {
+		// No DoNotSaveSetting() here - memStickDirectory isn't an ordinary setting and never gets
+		// written to ppsspp.ini, since the ini itself lives inside the memory stick directory.
+		g_Config.nandRootDirectory = Path(nand.value());
+	}
+
 	if (resolutionScale.has_value()) {
 		g_Config.iInternalResolution = resolutionScale.value();
 		g_Config.DoNotSaveSetting(&g_Config.iInternalResolution);

Core/CmdLine.h

@@ -59,6 +59,8 @@ struct CommandLineOptions {
 	std::optional<std::string> appendConfig;
 	std::optional<std::string> root;  // This is supposed to configure host0:.
 
+	std::optional<std::string> nand;  // Set the root nand directory (one level above flash0, ...)
+
 	// Memory stick root (the directory containing PSP/GAME, PSP/SYSTEM, ...). Mainly for headless,
 	// which otherwise always uses "memstick" next to the executable - so testing a real game there
 	// meant copying it in. Points at the same layout the app uses, so the two can share one.

Core/Config.h

@@ -706,7 +706,7 @@ public:
 	Path defaultCurrentDirectory;  // Platform dependent, initialized at startup.
 
 	Path memStickDirectory;
-	Path flash0Directory;
+	Path nandRootDirectory;
 	Path internalDataDirectory;
 	Path appCacheDirectory;
 

Core/CoreParameter.h

@@ -59,9 +59,12 @@ struct CoreParameter {
 	bool enableSound = true;  // there aren't multiple sound cores.
 
 	Path fileToStart;
+
 	Path mountIso;  // If non-empty, and fileToStart is an ELF or PBP, will mount this ISO in the background to umd1:.
 	Path mountRoot;  // If non-empty, and fileToStart is an ELF or PBP, mount this as host0:.
 
+	Path nandRoot;  // If non-empty, use this directory as the root above flash0:-flash3: (which are hosted in subdirectories flash0-flash3 of it).
+
 	std::string errorString;
 	bool loadGameConfigs = true;
 

Core/FileSystems/MetaFileSystem.cpp

@@ -195,6 +195,7 @@ int MetaFileSystem::MapFilePath(std::string_view _inpath, std::string *outpath,
 
 	// Special handling: host0:command.txt (as seen in Super Monkey Ball Adventures, for example)
 	// appears to mean the current directory on the UMD.
+	// Actually, not sure if this is still needed. It doesn't make a whole lot of sense.
 	if (startsWithNoCase(inpath.c_str(), "host0:") && !host0Mapped_) {
 		inpath = "umd0:" + inpath.substr(strlen("host0:"));
 	}

Core/Reporting.cpp

@@ -558,12 +558,6 @@ namespace Reporting
 		if (PSP_GetBootState() == BootState::Complete && g_paramSFO.GetValueString("DISC_VERSION").empty())
 			return false;
 
-		// Some users run the exe from a zip or something, and don't have fonts.
-		// This breaks things, but let's not report it since it's confusing.
-		File::FileInfo fo;
-		if (!File::Exists(g_Config.flash0Directory / "font/jpn0.pgf") || !g_VFS.GetFileInfo("flash0/font/jpn0.pgf", &fo))
-			return false;
-
 		return !everUnsupported;
 	}
 

Core/System.cpp

@@ -300,12 +300,6 @@ static void ShowCompatWarnings(const Compatibility &compat) {
 extern const std::string INDEX_FILENAME;
 
 static void MountFileSystems() {
-	// TODO: Revisit this flash0 configurability. It was added for 
-#if PPSSPP_PLATFORM(WINDOWS) || PPSSPP_PLATFORM(MACOS)
-	auto flash0System = std::make_shared<DirectoryFileSystem>(&pspFileSystem, g_Config.flash0Directory, FileSystemFlags::FLASH);
-#else
-	auto flash0System = std::make_shared<VFSFileSystem>(&pspFileSystem, "flash0");
-#endif
 	FileSystemFlags memstickFlags = FileSystemFlags::SIMULATE_FAT32 | FileSystemFlags::CARD;
 
 	Path pspDir = GetSysDirectory(DIRECTORY_PSP);
@@ -322,10 +316,13 @@ static void MountFileSystems() {
 	pspFileSystem.Mount("fatms:", memstickSystem);
 	pspFileSystem.Mount("pfat0:", memstickSystem);
 
+	// TODO: These should be made "lazy" mounts.
+	auto flash0System = std::make_shared<DirectoryFileSystem>(&pspFileSystem, g_Config.nandRootDirectory / "flash0", FileSystemFlags::FLASH);
+	auto flash1System = std::make_shared<DirectoryFileSystem>(&pspFileSystem, g_Config.nandRootDirectory / "flash1", FileSystemFlags::FLASH);
 	pspFileSystem.Mount("flash0:", flash0System);
+	pspFileSystem.Mount("flash1:", flash1System);
 
 	// NOTE: We don't handle the host0: mount here, it's in Load_PSP_ELF_PBP.
-	// Additionally, host0: is remapped to umd0: if there is an UMD inserted (old hack in MetaFileSystem).
 
 	if (g_RemasterMode) {
 		const std::string gameId = g_paramSFO.GetDiscID();

Core/Util/PathUtil.cpp

@@ -112,6 +112,8 @@ Path GetSysDirectory(PSPDirectories directoryType) {
 		return pspDirectory / "shaders";
 	case DIRECTORY_CUSTOM_THEMES:
 		return pspDirectory / "themes";
+	case DIRECTORY_NAND:
+		return pspDirectory / "NAND";
 
 	case DIRECTORY_MEMSTICK_ROOT:
 		return g_Config.memStickDirectory;

Core/Util/PathUtil.h

@@ -11,6 +11,7 @@ enum PSPDirectories {
 	DIRECTORY_CHEATS,
 	DIRECTORY_SCREENSHOT,
 	DIRECTORY_SYSTEM,
+	DIRECTORY_NAND,
 	DIRECTORY_GAME,
 	DIRECTORY_SAVEDATA,
 	DIRECTORY_PAUTH,

UI/NativeApp.cpp

@@ -595,11 +595,6 @@ void NativeInit(int argc, const char *argv[], const CommandLineOptions &cmdLineO
 		g_Config.defaultCurrentDirectory = Path(external_dir);
 	}
 
-	// Might also add an option to move it to internal / non-visible storage, but there's
-	// little point, really.
-
-	g_Config.flash0Directory = Path(external_dir) / "flash0";
-
 	Path memstickDirFile = g_Config.internalDataDirectory / "memstick_dir.txt";
 	if (File::Exists(memstickDirFile)) {
 		INFO_LOG(Log::System, "Reading '%s' to find memstick dir.", memstickDirFile.c_str());
@@ -650,13 +645,10 @@ void NativeInit(int argc, const char *argv[], const CommandLineOptions &cmdLineO
 #elif PPSSPP_PLATFORM(IOS)
 	g_Config.defaultCurrentDirectory = g_Config.internalDataDirectory;
 	g_Config.memStickDirectory = DarwinFileSystemServices::appropriateMemoryStickDirectoryToUse();
-	g_Config.flash0Directory = Path(external_dir) / "flash0";
 #elif PPSSPP_PLATFORM(MAC)
 	g_Config.memStickDirectory = DarwinFileSystemServices::appropriateMemoryStickDirectoryToUse();
-	g_Config.flash0Directory = Path(external_dir) / "flash0";
 #elif PPSSPP_PLATFORM(SWITCH)
 	g_Config.memStickDirectory = g_Config.internalDataDirectory / "config/ppsspp";
-	g_Config.flash0Directory = g_Config.internalDataDirectory / "assets/flash0";
 #elif PPSSPP_PLATFORM(WINDOWS)
 	// ...
 #else
@@ -669,7 +661,6 @@ void NativeInit(int argc, const char *argv[], const CommandLineOptions &cmdLineO
 		config = "./config";
 
 	g_Config.memStickDirectory = Path(config) / "ppsspp";
-	g_Config.flash0Directory = File::GetExeDirectory() / "assets/flash0";
 	if (getenv("HOME") != nullptr) {
 		g_Config.defaultCurrentDirectory = Path(getenv("HOME"));
 	} else {
@@ -683,6 +674,9 @@ void NativeInit(int argc, const char *argv[], const CommandLineOptions &cmdLineO
 		g_Config.currentDirectory = g_Config.defaultCurrentDirectory;
 	}
 
+	// Mount a filesystem
+	g_Config.nandRootDirectory = GetSysDirectory(DIRECTORY_NAND);
+
 	if (cache_dir && strlen(cache_dir)) {
 		g_Config.appCacheDirectory = Path(cache_dir);
 		DiskCachingFileLoaderCache::SetCacheDir(g_Config.appCacheDirectory);
@@ -702,7 +696,7 @@ void NativeInit(int argc, const char *argv[], const CommandLineOptions &cmdLineO
 
 	boot_filename.clear();
 	if (boot_filename.empty() && cmdLineOptions.bootVSH.has_value() && cmdLineOptions.bootVSH.value()) {
-		boot_filename = g_Config.flash0Directory / "vsh/module/vshmain.prx";
+		boot_filename = g_Config.nandRootDirectory / "flash0/vsh/module/vshmain.prx";
 	}
 
 	if (cmdLineOptions.appendConfig.has_value()) {

UWP/App.cpp

@@ -61,14 +61,14 @@ void App::InitialPPSSPP() {
 	g_VFS.Register("", new DirectoryReader(exePath / "Content"));
 	g_VFS.Register("", new DirectoryReader(exePath));
 
-	// Mount a filesystem
-	g_Config.flash0Directory = exePath / "assets/flash0";
-
 	// Prepare for initialization
 	std::wstring internalDataFolderW = std::wstring(winrt::Windows::Storage::ApplicationData::Current().LocalFolder().Path());
 	g_Config.internalDataDirectory = Path(internalDataFolderW);
 	g_Config.memStickDirectory = g_Config.internalDataDirectory;
 
+	// Mount a filesystem
+	g_Config.nandRootDirectory = GetSysDirectory(PSPDirectories::DIRECTORY_NAND);
+
 	// On Win32 it makes more sense to initialize the system directories here
 	// because the next place it was called was in the EmuThread, and it's too late by then.
 	CreateSysDirectories();

Windows/main.cpp

@@ -927,12 +927,10 @@ std::vector<std::wstring> GetWideCmdLine() {
 }
 
 static void InitMemstickDirectory() {
-	if (!g_Config.memStickDirectory.empty() && !g_Config.flash0Directory.empty())
+	if (!g_Config.memStickDirectory.empty() && !g_Config.nandRootDirectory.empty())
 		return;
 
 	const Path &exePath = File::GetExeDirectory();
-	// Mount a filesystem
-	g_Config.flash0Directory = exePath / "assets/flash0";
 
 	// Caller sets this to the Documents folder.
 	const Path rootMyDocsPath = g_Config.internalDataDirectory;

headless/Headless.cpp

@@ -782,11 +782,11 @@ int main(int argc, const char* argv[]) {
 	coreParameter.fastForward = true;
 
 	Path exePath = File::GetExeDirectory();
-	g_Config.flash0Directory = exePath / "assets/flash0";
 
 	// --memstick, applied by ApplyToConfig() further up, wins. This runs after it, so without the
 	// check the default below would silently overwrite whatever was asked for.
 	if (!cmdLineOptions.memStick.has_value()) {
+		// TODO: Share this derivation with the main build.
 #if PPSSPP_PLATFORM(WINDOWS)
 		// Mount a filesystem
 		g_Config.memStickDirectory = exePath / "memstick";
@@ -796,12 +796,14 @@ int main(int argc, const char* argv[]) {
 		g_Config.memStickDirectory = Path(std::string(getenv("HOME"))) / ".ppsspp";
 #endif
 	}
+	g_Config.nandRootDirectory = GetSysDirectory(DIRECTORY_NAND);
+	coreParameter.nandRoot = g_Config.nandRootDirectory;
 
-	// Try to find the flash0 directory.  Often this is from a subdirectory.
+	// Try to find the assets flash0 directory. Often this is from a subdirectory.
+	// This is needed for our fallback fonts.
 	Path nextPath = exePath;
 	for (int i = 0; i < 5; ++i) {
 		if (File::Exists(nextPath / "assets/flash0")) {
-			g_Config.flash0Directory = nextPath / "assets/flash0";
 #if !PPSSPP_PLATFORM(ANDROID)
 			g_VFS.Register("", new DirectoryReader(nextPath / "assets"));
 #endif
@@ -847,8 +849,9 @@ int main(int argc, const char* argv[]) {
 	UpdateUIState(UISTATE_INGAME);
 
 	if (cmdLineOptions.bootVSH.has_value() && cmdLineOptions.bootVSH.value()) {
-		AddToTestsByPath(&testFilenames, (g_Config.flash0Directory / "vsh/module/vshmain.prx").ToString());
+		AddToTestsByPath(&testFilenames, (coreParameter.nandRoot / "flash0/vsh/module/vshmain.prx").ToString());
 	}
+
 	if (testFilenames.empty()) {
 		return printUsage(cmdLineOptions, argv[0], argc <= 1 ? NULL : "No executables specified");
 	}

libretro/libretro.cpp

@@ -1267,10 +1267,10 @@ void retro_init(void)
    g_Config.currentDirectory = retro_base_dir;
    g_Config.defaultCurrentDirectory = retro_base_dir;
    g_Config.memStickDirectory = retro_save_dir;
-   g_Config.flash0Directory = retro_base_dir / "flash0";
    g_Config.internalDataDirectory = retro_base_dir;
    g_Config.bEnableNetworkChat = false;
    g_Config.bDiscordRichPresence = false;
+   g_Config.nandRootDirectory = GetSysDirectory(PSPDirectories::DIRECTORY_NAND);
 
    g_VFS.Register("", new DirectoryReader(retro_base_dir));