nvdrv: stub device for nvgpu nodes Switch 1 never had

Unknown /dev/nvhost-* nodes (first: /dev/nvhost-tsg-gpu, opened by the
Switch 2 NvRm during NVN device init) open as nx2_stub_device: every
ioctl succeeds with the input echoed and the rest zeroed, and is logged.
With this NVN device init completes and the title reaches
nn::wsi::ounce::native::NativeWindow::Acquire (first frame).

4 files changed, 72 insertions, 0 deletions

diff --git a/src/core/CMakeLists.txt b/src/core/CMakeLists.txt
index 231f0db451..6058ce82ce 100644
--- a/src/core/CMakeLists.txt
+++ b/src/core/CMakeLists.txt
@@ -866,6 +866,7 @@ add_library(core STATIC
     hle/service/nvdrv/devices/nvhost_vic.h
     hle/service/nvdrv/devices/nvmap.cpp
     hle/service/nvdrv/devices/nvmap.h
+    hle/service/nvdrv/devices/nx2_stub_device.h
     hle/service/nvdrv/nvdata.h
     hle/service/nvdrv/nvdrv.cpp
     hle/service/nvdrv/nvdrv.h
diff --git a/src/core/hle/service/nvdrv/devices/nx2_stub_device.h b/src/core/hle/service/nvdrv/devices/nx2_stub_device.h
new file mode 100644
index 0000000000..1dc2f8b7fa
--- /dev/null
+++ b/src/core/hle/service/nvdrv/devices/nx2_stub_device.h
@@ -0,0 +1,54 @@
+// SPDX-FileCopyrightText: Copyright 2026 Eden Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#pragma once
+
+#include <algorithm>
+#include <string>
+
+#include "common/logging.h"
+#include "core/hle/service/nvdrv/devices/nvdevice.h"
+
+namespace Service::Nvidia::Devices {
+
+// Device node that Switch 2 nvgpu drivers open but Switch 1 never had (e.g. /dev/nvhost-tsg-gpu).
+// Every ioctl succeeds with a zeroed reply and is logged, so the driver's use of it shows up.
+class nx2_stub_device final : public nvdevice {
+public:
+    explicit nx2_stub_device(Core::System& system_, std::string name_)
+        : nvdevice{system_}, name{std::move(name_)} {}
+
+    NvResult Ioctl1(DeviceFD fd, Ioctl command, std::span<const u8> input,
+                    std::span<u8> output) override {
+        return Stub(fd, command, input, output, {});
+    }
+    NvResult Ioctl2(DeviceFD fd, Ioctl command, std::span<const u8> input,
+                    std::span<const u8> inline_input, std::span<u8> output) override {
+        return Stub(fd, command, input, output, {});
+    }
+    NvResult Ioctl3(DeviceFD fd, Ioctl command, std::span<const u8> input, std::span<u8> output,
+                    std::span<u8> inline_output) override {
+        return Stub(fd, command, input, output, inline_output);
+    }
+
+    void OnOpen(NvCore::SessionId session_id, DeviceFD fd) override {
+        LOG_WARNING(Service_NVDRV, "(STUBBED) {} opened as fd {}", name, fd);
+    }
+    void OnClose(DeviceFD fd) override {}
+
+private:
+    NvResult Stub(DeviceFD fd, Ioctl command, std::span<const u8> input, std::span<u8> output,
+                  std::span<u8> inline_output) {
+        LOG_WARNING(Service_NVDRV, "(STUBBED) {} fd={} ioctl={:08X} group={:01X} command={:02X} in={:#x}",
+                    name, fd, command.raw, command.group, command.cmd, input.size());
+        // Echo the input (in/out ioctls keep their fields), zero the rest.
+        std::fill(output.begin(), output.end(), u8{0});
+        std::copy_n(input.begin(), std::min(input.size(), output.size()), output.begin());
+        std::fill(inline_output.begin(), inline_output.end(), u8{0});
+        return NvResult::Success;
+    }
+
+    std::string name;
+};
+
+} // namespace Service::Nvidia::Devices
diff --git a/src/core/hle/service/nvdrv/nvdrv.cpp b/src/core/hle/service/nvdrv/nvdrv.cpp
index b252a2efa5..5cac2693c5 100644
--- a/src/core/hle/service/nvdrv/nvdrv.cpp
+++ b/src/core/hle/service/nvdrv/nvdrv.cpp
@@ -23,6 +23,7 @@
 #include "core/hle/service/nvdrv/devices/nvhost_nvjpg.h"
 #include "core/hle/service/nvdrv/devices/nvhost_vic.h"
 #include "core/hle/service/nvdrv/devices/nvmap.h"
+#include "core/hle/service/nvdrv/devices/nx2_stub_device.h"
 #include "core/hle/service/nvdrv/nvdrv.h"
 #include "core/hle/service/nvdrv/nvdrv_interface.h"
 #include "core/hle/service/nvdrv/nvmemp.h"
@@ -125,6 +126,11 @@ void LoopProcess(Core::System& system) {
 
 Module::Module(Core::System& system)
     : container{system.Host1x()}, service_context{system, "nvdrv"}, events_interface{*this} {
+    nx2_stub_builder = [this, &system](DeviceFD fd, const std::string& name) {
+        auto device = std::make_shared<Devices::nx2_stub_device>(system, name);
+        open_files.emplace(fd, device);
+        return std::static_pointer_cast<Devices::nvdevice>(device);
+    };
     builders["/dev/nvhost-as-gpu"] = [this, &system](DeviceFD fd) {
         auto device = std::make_shared<Devices::nvhost_as_gpu>(system, *this, container);
         return open_files.emplace(fd, std::move(device)).first;
@@ -181,6 +187,15 @@ NvResult Module::VerifyFD(DeviceFD fd) const {
 
 DeviceFD Module::Open(const std::string& device_name, NvCore::SessionId session_id) {
     auto it = builders.find(device_name);
+    if (it == builders.end() && device_name.starts_with("/dev/nvhost-")) {
+        // Newer nvgpu nodes used by Switch 2 drivers (e.g. /dev/nvhost-tsg-gpu): serve them with
+        // a logged stub instead of failing the open.
+        LOG_WARNING(Service_NVDRV, "Opening unknown device {} as a Switch 2 stub", device_name);
+        const DeviceFD fd = next_fd++;
+        auto device = nx2_stub_builder(fd, device_name);
+        device->OnOpen(session_id, fd);
+        return fd;
+    }
     if (it == builders.end()) {
         LOG_ERROR(Service_NVDRV, "Trying to open unknown device {}", device_name);
         return INVALID_NVDRV_FD;
diff --git a/src/core/hle/service/nvdrv/nvdrv.h b/src/core/hle/service/nvdrv/nvdrv.h
index f503f108c3..ba8ab6a40e 100644
--- a/src/core/hle/service/nvdrv/nvdrv.h
+++ b/src/core/hle/service/nvdrv/nvdrv.h
@@ -98,6 +98,8 @@ private:
     friend class EventInterface;
 
     /// Manages syncpoints on the host
+    /// Builds a logged stub for nvgpu device nodes only Switch 2 drivers use.
+    std::function<std::shared_ptr<Devices::nvdevice>(DeviceFD, const std::string&)> nx2_stub_builder;
     NvCore::Container container;
 
     /// Id to use for the next open file descriptor.