Updated the audout:u and IAudioOut, now it might work with RetroArch without trigger an assert, however it's not the ideal implementation

src/core/hle/service/audio/audout_u.cpp

@@ -3,30 +3,140 @@
 // Refer to the license.txt file included.
 
 #include "common/logging/log.h"
+#include "core/core_timing.h"
 #include "core/hle/ipc_helpers.h"
 #include "core/hle/kernel/hle_ipc.h"
+#include "core/hle/kernel/event.h"
 #include "core/hle/service/audio/audout_u.h"
 
 namespace Service {
 namespace Audio {
 
+// switch sample rate frequency
+constexpr u32 sample_rate = 48000;
+// TODO(st4rk): dynamic number of channels, as I think Switch has support
+// to more audio channels (probably when Docked I guess)
+constexpr u32 audio_channels = 2;
+// TODO(st4rk): find a proper value for the audio_ticks
+constexpr u64 audio_ticks = static_cast<u64>(BASE_CLOCK_RATE / 1000);
+
 class IAudioOut final : public ServiceFramework<IAudioOut> {
 public:
     IAudioOut() : ServiceFramework("IAudioOut") {
         static const FunctionInfo functions[] = {
             {0x0, nullptr, "GetAudioOutState"},
-            {0x1, nullptr, "StartAudioOut"},
-            {0x2, nullptr, "StopAudioOut"},
-            {0x3, nullptr, "AppendAudioOutBuffer_1"},
-            {0x4, nullptr, "RegisterBufferEvent"},
-            {0x5, nullptr, "GetReleasedAudioOutBuffer_1"},
+            {0x1, &IAudioOut::StartAudioOut, "StartAudioOut"},
+            {0x2, &IAudioOut::StopAudioOut, "StopAudioOut"},
+            {0x3, &IAudioOut::AppendAudioOutBuffer_1, "AppendAudioOutBuffer_1"},
+            {0x4, &IAudioOut::RegisterBufferEvent, "RegisterBufferEvent"},
+            {0x5, &IAudioOut::GetReleasedAudioOutBuffer_1, "GetReleasedAudioOutBuffer_1"},
             {0x6, nullptr, "ContainsAudioOutBuffer"},
             {0x7, nullptr, "AppendAudioOutBuffer_2"},
             {0x8, nullptr, "GetReleasedAudioOutBuffer_2"},
         };
         RegisterHandlers(functions);
+
+        // This is the event handle used to check if the audio buffer was released
+        buffer_event = Kernel::Event::Create(Kernel::ResetType::OneShot, "IAudioOut buffer released event handle");
+
+        // Register event callback to update the Audio Buffer
+        audio_event = CoreTiming::RegisterEvent(
+            "IAudioOut::UpdateAudioBuffersCallback",
+            [this](u64 userdata, int cycles_late) {
+                UpdateAudioBuffersCallback();
+                CoreTiming::ScheduleEvent(audio_ticks - cycles_late, audio_event);
+            });
+
+        // Start the audio event
+        CoreTiming::ScheduleEvent(audio_ticks, audio_event);
+
+        // start with the audio stopped
+        audio_out_state = 1;
     }
+
     ~IAudioOut() = default;
+private:
+
+    void StartAudioOut(Kernel::HLERequestContext& ctx) {
+        LOG_WARNING(Service, "(STUBBED) called");
+
+        // start audio
+        audio_out_state = 0x0;
+
+        IPC::RequestBuilder rb{ctx, 2, 0, 0, 0};
+        rb.Push(RESULT_SUCCESS);
+    }
+
+    void StopAudioOut(Kernel::HLERequestContext& ctx) {
+        LOG_WARNING(Service, "(STUBBED) called");
+
+        // stop audio
+        audio_out_state = 0x1;
+
+        IPC::RequestBuilder rb{ctx, 2, 0, 0, 0};
+        rb.Push(RESULT_SUCCESS);
+    }
+
+    void RegisterBufferEvent(Kernel::HLERequestContext& ctx) {
+        LOG_WARNING(Service, "(STUBBED) called");
+
+        IPC::RequestBuilder rb{ctx, 2, 1};
+        rb.Push(RESULT_SUCCESS);
+        rb.PushCopyObjects(buffer_event);
+    }
+
+    void AppendAudioOutBuffer_1(Kernel::HLERequestContext& ctx) {
+        LOG_WARNING(Service, "(STUBBED) called");
+        IPC::RequestParser rp{ctx};
+
+        released_buffer = rp.Pop<u64>();
+
+        IPC::RequestBuilder rb{ctx, 2, 0, 0, 0};
+        rb.Push(RESULT_SUCCESS);
+    }
+
+    void GetReleasedAudioOutBuffer_1(Kernel::HLERequestContext& ctx) {
+        LOG_WARNING(Service, "(STUBBED) called");
+
+        const auto& buffer = ctx.BufferDescriptorB()[0];
+
+        // TODO(st4rk): this is how libtransistor currently implements the
+        // GetReleasedAudioOutBuffer, it should return the key (a VA) to
+        // the APP and this address is used to know which buffer should
+        // be filled with data and send again to the service through
+        // AppendAudioOutBuffer. Check if this is the proper way to
+        // do it.
+
+        Memory::WriteBlock(buffer.Address(), &released_buffer, sizeof(u64));
+
+        IPC::RequestBuilder rb{ctx, 3, 0, 0, 0};
+        rb.Push(RESULT_SUCCESS);
+        // This might be the total of released buffers
+        rb.Push<u32>(0);
+    }
+
+    void UpdateAudioBuffersCallback() {
+        if (!audio_out_state) {
+            buffer_event->Signal();
+        }
+    }
+
+    // This is used to trigger the audio event callback that is going
+    // to read the samples from the audio_buffer list and enqueue the samples
+    // using the sink (audio_core).
+    CoreTiming::EventType* audio_event;
+
+    // This is the evend handle used to check if the audio buffer was released
+    Kernel::SharedPtr<Kernel::Event> buffer_event;
+
+    // (st4rk): this is just a temporary workaround for the future implementation.
+    // Libtransistor uses the key as an address in the App, so we need to return
+    // when the GetReleasedAudioOutBuffer_1 is called, otherwise we'll run in
+    // problems, because libtransistor uses the key returned as an pointer;
+    u64 released_buffer;
+
+    // current audio state: 0 is started and 1 is stopped
+    u32 audio_out_state;
 };
 
 void AudOutU::ListAudioOuts(Kernel::HLERequestContext& ctx) {
@@ -52,14 +162,25 @@ void AudOutU::ListAudioOuts(Kernel::HLERequestContext& ctx) {
 void AudOutU::OpenAudioOut(Kernel::HLERequestContext& ctx) {
     LOG_WARNING(Service, "(STUBBED) called");
 
-    IPC::RequestBuilder rb{ctx, 6};
+    if (audio_out_interface == nullptr) {
+        audio_out_interface = std::make_shared<IAudioOut>();
+    }
+
+    auto sessions = Kernel::ServerSession::CreateSessionPair(audio_out_interface->GetServiceName());
+    auto server = std::get<Kernel::SharedPtr<Kernel::ServerSession>>(sessions);
+    auto client = std::get<Kernel::SharedPtr<Kernel::ClientSession>>(sessions);
+    audio_out_interface->ClientConnected(server);
+    LOG_DEBUG(Service, "called, initialized IAudioOut -> session=%u",
+              client->GetObjectId());
+    IPC::RequestBuilder rb{ctx, 6,0,1};
 
     rb.Push(RESULT_SUCCESS);
-    rb.Push<u32>(48000); // Sample Rate
-    rb.Push<u32>(2);     // Channels
-    rb.Push<u32>(2);     // PCM Format (INT16)
-    rb.Push<u32>(0);     // Unknown
-    rb.PushIpcInterface<Audio::IAudioOut>();
+    rb.Push<u32>(sample_rate);
+    rb.Push<u32>(audio_channels);
+    rb.Push<u32>(PCM_FORMAT::INT16);
+    // this field is unknown
+    rb.Push<u32>(0);
+    rb.PushMoveObjects(std::move(client));
 }
 
 AudOutU::AudOutU() : ServiceFramework("audout:u") {

src/core/hle/service/audio/audout_u.h

@@ -13,14 +13,28 @@ class HLERequestContext;
 namespace Service {
 namespace Audio {
 
+class IAudioOut;
+
 class AudOutU final : public ServiceFramework<AudOutU> {
 public:
     AudOutU();
     ~AudOutU() = default;
 
 private:
+    std::shared_ptr<IAudioOut> audio_out_interface;
+
     void ListAudioOuts(Kernel::HLERequestContext& ctx);
     void OpenAudioOut(Kernel::HLERequestContext& ctx);
+
+    enum PCM_FORMAT {
+        INVALID,
+        INT8,
+        INT16,
+        INT24,
+        INT32,
+        PCM_FLOAT,
+        ADPCM
+    };
 };
 
 } // namespace Audio