service: sm: Update to match official IPC interface

Updates the SM service implementation to better match the official
"nn::sm::detail::IUserInterface" interface. Key changes include:

- Replace Initialize with RegisterClient command (cmd 0)
- Add DetachClient command implementation (cmd 4)
- Update service name handling to use u64-encoded names
- Add proper PID descriptor handling for RegisterClient/DetachClient
- Add ResultNotAllowed error code
- Update handler registration for both CMIF and TIPC

This brings the implementation closer to the official documentation while
maintaining compatibility with existing code.

Refs: switchbrew.org/wiki/Services_API#sm:

src/core/hle/service/sm/sm.cpp

@@ -22,6 +22,7 @@ constexpr Result ResultInvalidClient(ErrorModule::SM, 2);
 constexpr Result ResultAlreadyRegistered(ErrorModule::SM, 4);
 constexpr Result ResultInvalidServiceName(ErrorModule::SM, 6);
 constexpr Result ResultNotRegistered(ErrorModule::SM, 7);
+constexpr Result ResultNotAllowed(ErrorModule::SM, 1);
 
 ServiceManager::ServiceManager(Kernel::KernelCore& kernel_) : kernel{kernel_} {
     controller_interface = std::make_unique<Controller>(kernel.System());
@@ -157,9 +158,10 @@ void SM::GetServiceTipc(HLERequestContext& ctx) {
 }
 
 static std::string PopServiceName(IPC::RequestParser& rp) {
-    auto name_buf = rp.PopRaw<std::array<char, 8>>();
+    const u64 name_encoded = rp.PopRaw<u64>();
     std::string result;
-    for (const auto& c : name_buf) {
+    for (int i = 0; i < 8; i++) {
+        const char c = static_cast<char>((name_encoded >> (i * 8)) & 0xFF);
         if (c >= ' ' && c <= '~') {
             result.push_back(c);
         }
@@ -250,22 +252,48 @@ void SM::UnregisterService(HLERequestContext& ctx) {
     rb.Push(service_manager.UnregisterService(name));
 }
 
+void SM::RegisterClient(HLERequestContext& ctx) {
+    LOG_DEBUG(Service_SM, "called");
+
+    IPC::RequestParser rp{ctx};
+
+    // Read PID descriptor
+    rp.Skip(2, false); // Skip PID descriptor and reserved u64
+
+    ctx.GetManager()->SetIsInitializedForSm();
+
+    IPC::ResponseBuilder rb{ctx, 2};
+    rb.Push(ResultSuccess);
+}
+
+void SM::DetachClient(HLERequestContext& ctx) {
+    LOG_DEBUG(Service_SM, "called");
+
+    IPC::RequestParser rp{ctx};
+    rp.Skip(2, false); // Skip PID descriptor and reserved u64
+
+    ctx.GetManager()->SetIsInitializedForSm();
+
+    IPC::ResponseBuilder rb{ctx, 2};
+    rb.Push(ResultSuccess);
+}
+
 SM::SM(ServiceManager& service_manager_, Core::System& system_)
     : ServiceFramework{system_, "sm:", 4},
       service_manager{service_manager_}, kernel{system_.Kernel()} {
     RegisterHandlers({
-        {0, &SM::Initialize, "Initialize"},
+        {0, &SM::RegisterClient, "RegisterClient"},
         {1, &SM::GetServiceCmif, "GetService"},
         {2, &SM::RegisterServiceCmif, "RegisterService"},
         {3, &SM::UnregisterService, "UnregisterService"},
-        {4, nullptr, "DetachClient"},
+        {4, &SM::DetachClient, "DetachClient"},
     });
     RegisterHandlersTipc({
-        {0, &SM::Initialize, "Initialize"},
+        {0, &SM::RegisterClient, "RegisterClient"},
         {1, &SM::GetServiceTipc, "GetService"},
         {2, &SM::RegisterServiceTipc, "RegisterService"},
         {3, &SM::UnregisterService, "UnregisterService"},
-        {4, nullptr, "DetachClient"},
+        {4, &SM::DetachClient, "DetachClient"},
     });
 }
 

src/core/hle/service/sm/sm.h

@@ -38,12 +38,14 @@ public:
     ~SM() override;
 
 private:
+    void RegisterClient(HLERequestContext& ctx);
     void Initialize(HLERequestContext& ctx);
     void GetServiceCmif(HLERequestContext& ctx);
     void GetServiceTipc(HLERequestContext& ctx);
     void RegisterServiceCmif(HLERequestContext& ctx);
     void RegisterServiceTipc(HLERequestContext& ctx);
     void UnregisterService(HLERequestContext& ctx);
+    void DetachClient(HLERequestContext& ctx);
 
     Result GetServiceImpl(Kernel::KClientSession** out_client_session, HLERequestContext& ctx);
     void RegisterServiceImpl(HLERequestContext& ctx, std::string name, u32 max_session_count,