sceReg: Let a key read a bool setting, use it for VSH UMD autoboot

KeyValue gets an optional pointer to a g_Config bool, which the key
reads as 0/1. The setting wins over guest writes: since category_version
is kept low, the VSH upgrades the registry at every boot and rewrites
every key with its default.

/CONFIG/SYSTEM/umd_autoboot reads the new SystemParam VshUmdAutoboot
(default true, as before). Turned off, --vsh --mount stays in the XMB
with the disc in the Game column instead of starting it.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

Core/Config.cpp

@@ -1121,6 +1121,7 @@ static const ConfigSetting systemParamSettings[] = {
 	ConfigSetting("BypassOSKWithKeyboard", SETTING(g_Config, bBypassOSKWithKeyboard), false, CfgFlag::PER_GAME),
 	ConfigSetting("WlanPowerSave", SETTING(g_Config, bWlanPowerSave), (bool) PSP_SYSTEMPARAM_WLAN_POWERSAVE_OFF, CfgFlag::PER_GAME),
 	ConfigSetting("EncryptSave", SETTING(g_Config, bEncryptSave), true, CfgFlag::PER_GAME | CfgFlag::REPORT),
+	ConfigSetting("VshUmdAutoboot", SETTING(g_Config, bVshUmdAutoboot), true, CfgFlag::DEFAULT),
 	ConfigSetting("MemStickSize", SETTING(g_Config, iMemStickSizeGB), 16, CfgFlag::DEFAULT),
 	ConfigSetting("FuseID", SETTING(g_Config, sFuseID), "", CfgFlag::DEFAULT),
 };

Core/Config.h

@@ -594,6 +594,8 @@ public:
 	int iButtonPreference;
 	int iLockParentalLevel;
 	bool bEncryptSave;
+	// /CONFIG/SYSTEM/umd_autoboot: whether the VSH starts an inserted disc by itself.
+	bool bVshUmdAutoboot;
 
 	// Networking
 	bool bEnableAdhocServer;

Core/HLE/sceReg.cpp

@@ -8,6 +8,7 @@
 #include "Common/Serialize/Serializer.h"
 #include "Common/Serialize/SerializeMap.h"
 #include "Common/StringUtils.h"
+#include "Core/Config.h"
 
 #define SYSTEM_REGISTRY "/system"
 #define REG_KEYNAME_SIZE 27
@@ -58,6 +59,9 @@ struct KeyValue {
 	const char *strValue;  // also can be used for bin. Note: can't be std::string/string_view, will cut off the length.
 	int intValue;
 	const KeyValue *dirContents;  // intValue is the count.
+	// If set, an INT key reads this setting (as 0 or 1), even after the guest writes it: the VSH
+	// rewrites every key with its default at each boot, since category_version is below its schema.
+	const bool *boolSetting = nullptr;
 };
 
 // Guest-written registry values (sceRegCreateKey / sceRegSetKeyValue), keyed by category path
@@ -764,7 +768,7 @@ static const KeyValue tree_CONFIG_SYSTEM_CHARACTER_SET[] = {
 static const KeyValue tree_CONFIG_SYSTEM[] = {
 	{ "owner_name", ValueType::STR, "P939", 5 },
 	{ "backlight_brightness", ValueType::INT, "", (int)0x3 },  // decimal: 3
-	{ "umd_autoboot", ValueType::INT, "", (int)0x1 },  // decimal: 1
+	{ "umd_autoboot", ValueType::INT, "", (int)0x1, nullptr, &g_Config.bVshUmdAutoboot },  // decimal: 1
 	{ "usb_charge", ValueType::INT, "", (int)0x1 },  // decimal: 1
 	{ "umd_cache", ValueType::INT, "", (int)0x1 },  // decimal: 1
 	{ "usb_auto_connect", ValueType::INT, "", (int)0x1 },  // decimal: 1
@@ -1090,6 +1094,12 @@ static const MergedCategory &GetMergedCategory(const std::string &path) {
 		}
 	}
 
+	for (auto &kv : merged.keyvals) {
+		if (kv.boolSetting) {
+			kv.intValue = *kv.boolSetting ? 1 : 0;
+		}
+	}
+
 	return merged;
 }