service/nvflinger,service/vi: Handle failure cases with exposed API

Converts many of the Find* functions to return a std::optional<T> as
opposed to returning the raw return values directly. This allows
removing a few assertions and handles error cases like the service
itself does.

src/core/hle/service/am/am.cpp

@@ -322,14 +322,15 @@ void ISelfController::SetScreenShotImageOrientation(Kernel::HLERequestContext& c
 
 void ISelfController::CreateManagedDisplayLayer(Kernel::HLERequestContext& ctx) {
     LOG_WARNING(Service_AM, "(STUBBED) called");
+
     // TODO(Subv): Find out how AM determines the display to use, for now just
     // create the layer in the Default display.
-    u64 display_id = nvflinger->OpenDisplay("Default");
+    const auto display_id = nvflinger->OpenDisplay("Default");
-    u64 layer_id = nvflinger->CreateLayer(display_id);
+    const auto layer_id = nvflinger->CreateLayer(*display_id);
 
     IPC::ResponseBuilder rb{ctx, 4};
     rb.Push(RESULT_SUCCESS);
-    rb.Push(layer_id);
+    rb.Push(*layer_id);
 }
 
 void ISelfController::SetHandlesRequestToDisplay(Kernel::HLERequestContext& ctx) {

src/core/hle/service/nvflinger/nvflinger.cpp

@@ -46,7 +46,7 @@ void NVFlinger::SetNVDrvInstance(std::shared_ptr<Nvidia::Module> instance) {
     nvdrv = std::move(instance);
 }
 
-u64 NVFlinger::OpenDisplay(std::string_view name) {
+std::optional<u64> NVFlinger::OpenDisplay(std::string_view name) {
     LOG_DEBUG(Service, "Opening \"{}\" display", name);
 
     // TODO(Subv): Currently we only support the Default display.
@@ -54,32 +54,48 @@ u64 NVFlinger::OpenDisplay(std::string_view name) {
 
     const auto itr = std::find_if(displays.begin(), displays.end(),
                                   [&](const Display& display) { return display.name == name; });
-
+    if (itr == displays.end()) {
-    ASSERT(itr != displays.end());
+        return {};
+    }
 
     return itr->id;
 }
 
-u64 NVFlinger::CreateLayer(u64 display_id) {
+std::optional<u64> NVFlinger::CreateLayer(u64 display_id) {
-    auto& display = FindDisplay(display_id);
+    auto* const display = FindDisplay(display_id);
 
-    ASSERT_MSG(display.layers.empty(), "Only one layer is supported per display at the moment");
+    if (display == nullptr) {
+        return {};
+    }
+
+    ASSERT_MSG(display->layers.empty(), "Only one layer is supported per display at the moment");
 
     const u64 layer_id = next_layer_id++;
     const u32 buffer_queue_id = next_buffer_queue_id++;
     auto buffer_queue = std::make_shared<BufferQueue>(buffer_queue_id, layer_id);
-    display.layers.emplace_back(layer_id, buffer_queue);
+    display->layers.emplace_back(layer_id, buffer_queue);
     buffer_queues.emplace_back(std::move(buffer_queue));
     return layer_id;
 }
 
-u32 NVFlinger::FindBufferQueueId(u64 display_id, u64 layer_id) const {
+std::optional<u32> NVFlinger::FindBufferQueueId(u64 display_id, u64 layer_id) const {
-    const auto& layer = FindLayer(display_id, layer_id);
+    const auto* const layer = FindLayer(display_id, layer_id);
-    return layer.buffer_queue->GetId();
+
+    if (layer == nullptr) {
+        return {};
+    }
+
+    return layer->buffer_queue->GetId();
 }
 
 Kernel::SharedPtr<Kernel::ReadableEvent> NVFlinger::FindVsyncEvent(u64 display_id) const {
-    return FindDisplay(display_id).vsync_event.readable;
+    auto* const display = FindDisplay(display_id);
+
+    if (display == nullptr) {
+        return nullptr;
+    }
+
+    return display->vsync_event.readable;
 }
 
 std::shared_ptr<BufferQueue> NVFlinger::FindBufferQueue(u32 id) const {
@@ -90,40 +106,60 @@ std::shared_ptr<BufferQueue> NVFlinger::FindBufferQueue(u32 id) const {
     return *itr;
 }
 
-Display& NVFlinger::FindDisplay(u64 display_id) {
+Display* NVFlinger::FindDisplay(u64 display_id) {
     const auto itr = std::find_if(displays.begin(), displays.end(),
                                   [&](const Display& display) { return display.id == display_id; });
 
-    ASSERT(itr != displays.end());
+    if (itr == displays.end()) {
-    return *itr;
+        return nullptr;
     }
 
-const Display& NVFlinger::FindDisplay(u64 display_id) const {
+    return &*itr;
+}
+
+const Display* NVFlinger::FindDisplay(u64 display_id) const {
     const auto itr = std::find_if(displays.begin(), displays.end(),
                                   [&](const Display& display) { return display.id == display_id; });
 
-    ASSERT(itr != displays.end());
+    if (itr == displays.end()) {
-    return *itr;
+        return nullptr;
     }
 
-Layer& NVFlinger::FindLayer(u64 display_id, u64 layer_id) {
+    return &*itr;
-    auto& display = FindDisplay(display_id);
-
-    const auto itr = std::find_if(display.layers.begin(), display.layers.end(),
-                                  [&](const Layer& layer) { return layer.id == layer_id; });
-
-    ASSERT(itr != display.layers.end());
-    return *itr;
 }
 
-const Layer& NVFlinger::FindLayer(u64 display_id, u64 layer_id) const {
+Layer* NVFlinger::FindLayer(u64 display_id, u64 layer_id) {
-    const auto& display = FindDisplay(display_id);
+    auto* const display = FindDisplay(display_id);
 
-    const auto itr = std::find_if(display.layers.begin(), display.layers.end(),
+    if (display == nullptr) {
+        return nullptr;
+    }
+
+    const auto itr = std::find_if(display->layers.begin(), display->layers.end(),
                                   [&](const Layer& layer) { return layer.id == layer_id; });
 
-    ASSERT(itr != display.layers.end());
+    if (itr == display->layers.end()) {
-    return *itr;
+        return nullptr;
+    }
+
+    return &*itr;
+}
+
+const Layer* NVFlinger::FindLayer(u64 display_id, u64 layer_id) const {
+    const auto* const display = FindDisplay(display_id);
+
+    if (display == nullptr) {
+        return nullptr;
+    }
+
+    const auto itr = std::find_if(display->layers.begin(), display->layers.end(),
+                                  [&](const Layer& layer) { return layer.id == layer_id; });
+
+    if (itr == display->layers.end()) {
+        return nullptr;
+    }
+
+    return &*itr;
 }
 
 void NVFlinger::Compose() {

src/core/hle/service/nvflinger/nvflinger.h

@@ -6,6 +6,7 @@
 
 #include <array>
 #include <memory>
+#include <optional>
 #include <string>
 #include <string_view>
 #include <vector>
@@ -58,15 +59,23 @@ public:
     void SetNVDrvInstance(std::shared_ptr<Nvidia::Module> instance);
 
     /// Opens the specified display and returns the ID.
-    u64 OpenDisplay(std::string_view name);
+    ///
+    /// If an invalid display name is provided, then an empty optional is returned.
+    std::optional<u64> OpenDisplay(std::string_view name);
 
     /// Creates a layer on the specified display and returns the layer ID.
-    u64 CreateLayer(u64 display_id);
+    ///
+    /// If an invalid display ID is specified, then an empty optional is returned.
+    std::optional<u64> CreateLayer(u64 display_id);
 
     /// Finds the buffer queue ID of the specified layer in the specified display.
-    u32 FindBufferQueueId(u64 display_id, u64 layer_id) const;
+    ///
+    /// If an invalid display ID or layer ID is provided, then an empty optional is returned.
+    std::optional<u32> FindBufferQueueId(u64 display_id, u64 layer_id) const;
 
     /// Gets the vsync event for the specified display.
+    ///
+    /// If an invalid display ID is provided, then nullptr is returned.
     Kernel::SharedPtr<Kernel::ReadableEvent> FindVsyncEvent(u64 display_id) const;
 
     /// Obtains a buffer queue identified by the ID.
@@ -78,16 +87,16 @@ public:
 
 private:
     /// Finds the display identified by the specified ID.
-    Display& FindDisplay(u64 display_id);
+    Display* FindDisplay(u64 display_id);
 
     /// Finds the display identified by the specified ID.
-    const Display& FindDisplay(u64 display_id) const;
+    const Display* FindDisplay(u64 display_id) const;
 
     /// Finds the layer identified by the specified ID in the desired display.
-    Layer& FindLayer(u64 display_id, u64 layer_id);
+    Layer* FindLayer(u64 display_id, u64 layer_id);
 
     /// Finds the layer identified by the specified ID in the desired display.
-    const Layer& FindLayer(u64 display_id, u64 layer_id) const;
+    const Layer* FindLayer(u64 display_id, u64 layer_id) const;
 
     std::shared_ptr<Nvidia::Module> nvdrv;
 

src/core/hle/service/vi/vi.cpp

@@ -34,6 +34,7 @@ namespace Service::VI {
 
 constexpr ResultCode ERR_OPERATION_FAILED{ErrorModule::VI, 1};
 constexpr ResultCode ERR_UNSUPPORTED{ErrorModule::VI, 6};
+constexpr ResultCode ERR_NOT_FOUND{ErrorModule::VI, 7};
 
 struct DisplayInfo {
     /// The name of this particular display.
@@ -838,11 +839,16 @@ private:
                     "(STUBBED) called. unknown=0x{:08X}, display=0x{:016X}, aruid=0x{:016X}",
                     unknown, display, aruid);
 
-        const u64 layer_id = nv_flinger->CreateLayer(display);
+        const auto layer_id = nv_flinger->CreateLayer(display);
+        if (!layer_id) {
+            IPC::ResponseBuilder rb{ctx, 2};
+            rb.Push(ERR_NOT_FOUND);
+            return;
+        }
 
         IPC::ResponseBuilder rb{ctx, 4};
         rb.Push(RESULT_SUCCESS);
-        rb.Push(layer_id);
+        rb.Push(*layer_id);
     }
 
     void AddToLayerStack(Kernel::HLERequestContext& ctx) {
@@ -950,9 +956,16 @@ private:
 
         ASSERT_MSG(name == "Default", "Non-default displays aren't supported yet");
 
+        const auto display_id = nv_flinger->OpenDisplay(name);
+        if (!display_id) {
+            IPC::ResponseBuilder rb{ctx, 2};
+            rb.Push(ERR_NOT_FOUND);
+            return;
+        }
+
         IPC::ResponseBuilder rb{ctx, 4};
         rb.Push(RESULT_SUCCESS);
-        rb.Push<u64>(nv_flinger->OpenDisplay(name));
+        rb.Push<u64>(*display_id);
     }
 
     void CloseDisplay(Kernel::HLERequestContext& ctx) {
@@ -1043,10 +1056,21 @@ private:
 
         LOG_DEBUG(Service_VI, "called. layer_id=0x{:016X}, aruid=0x{:016X}", layer_id, aruid);
 
-        const u64 display_id = nv_flinger->OpenDisplay(display_name);
+        const auto display_id = nv_flinger->OpenDisplay(display_name);
-        const u32 buffer_queue_id = nv_flinger->FindBufferQueueId(display_id, layer_id);
+        if (!display_id) {
+            IPC::ResponseBuilder rb{ctx, 2};
+            rb.Push(ERR_NOT_FOUND);
+            return;
+        }
 
-        NativeWindow native_window{buffer_queue_id};
+        const auto buffer_queue_id = nv_flinger->FindBufferQueueId(*display_id, layer_id);
+        if (!buffer_queue_id) {
+            IPC::ResponseBuilder rb{ctx, 2};
+            rb.Push(ERR_NOT_FOUND);
+            return;
+        }
+
+        NativeWindow native_window{*buffer_queue_id};
         IPC::ResponseBuilder rb{ctx, 4};
         rb.Push(RESULT_SUCCESS);
         rb.Push<u64>(ctx.WriteBuffer(native_window.Serialize()));
@@ -1062,13 +1086,24 @@ private:
 
         // TODO(Subv): What's the difference between a Stray and a Managed layer?
 
-        const u64 layer_id = nv_flinger->CreateLayer(display_id);
+        const auto layer_id = nv_flinger->CreateLayer(display_id);
-        const u32 buffer_queue_id = nv_flinger->FindBufferQueueId(display_id, layer_id);
+        if (!layer_id) {
+            IPC::ResponseBuilder rb{ctx, 2};
+            rb.Push(ERR_NOT_FOUND);
+            return;
+        }
 
-        NativeWindow native_window{buffer_queue_id};
+        const auto buffer_queue_id = nv_flinger->FindBufferQueueId(display_id, *layer_id);
+        if (!buffer_queue_id) {
+            IPC::ResponseBuilder rb{ctx, 2};
+            rb.Push(ERR_NOT_FOUND);
+            return;
+        }
+
+        NativeWindow native_window{*buffer_queue_id};
         IPC::ResponseBuilder rb{ctx, 6};
         rb.Push(RESULT_SUCCESS);
-        rb.Push(layer_id);
+        rb.Push(*layer_id);
         rb.Push<u64>(ctx.WriteBuffer(native_window.Serialize()));
     }
 
@@ -1089,6 +1124,11 @@ private:
         LOG_WARNING(Service_VI, "(STUBBED) called. display_id=0x{:016X}", display_id);
 
         const auto vsync_event = nv_flinger->FindVsyncEvent(display_id);
+        if (!vsync_event) {
+            IPC::ResponseBuilder rb{ctx, 2};
+            rb.Push(ERR_NOT_FOUND);
+            return;
+        }
 
         IPC::ResponseBuilder rb{ctx, 2, 1};
         rb.Push(RESULT_SUCCESS);