service/am: Unstub SetExpectedMasterVolume()

This function passes in the desired main applet and library applet
volume levels. We can then just pass those values back within the
relevant volume getter functions, allowing us to unstub those as well.

The initial values for the library and main applet volumes differ. The
main applet volume is 0.25 by default, while the library applet volume
is initialized to 1.0 by default in the services themselves.

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

@@ -2,10 +2,10 @@
 // Licensed under GPLv2 or any later version
 // Refer to the license.txt file included.
 
+#include <algorithm>
 #include <array>
 #include <cinttypes>
 #include <cstring>
-#include <stack>
 #include "audio_core/audio_renderer.h"
 #include "core/core.h"
 #include "core/file_sys/savedata_factory.h"
@@ -93,38 +93,50 @@ void IWindowController::AcquireForegroundRights(Kernel::HLERequestContext& ctx)
 }
 
 IAudioController::IAudioController() : ServiceFramework("IAudioController") {
+    // clang-format off
     static const FunctionInfo functions[] = {
         {0, &IAudioController::SetExpectedMasterVolume, "SetExpectedMasterVolume"},
-        {1, &IAudioController::GetMainAppletExpectedMasterVolume,
-         "GetMainAppletExpectedMasterVolume"},
-        {2, &IAudioController::GetLibraryAppletExpectedMasterVolume,
-         "GetLibraryAppletExpectedMasterVolume"},
+        {1, &IAudioController::GetMainAppletExpectedMasterVolume, "GetMainAppletExpectedMasterVolume"},
+        {2, &IAudioController::GetLibraryAppletExpectedMasterVolume, "GetLibraryAppletExpectedMasterVolume"},
         {3, nullptr, "ChangeMainAppletMasterVolume"},
         {4, nullptr, "SetTransparentVolumeRate"},
     };
+    // clang-format on
+
     RegisterHandlers(functions);
 }
 
 IAudioController::~IAudioController() = default;
 
 void IAudioController::SetExpectedMasterVolume(Kernel::HLERequestContext& ctx) {
-    LOG_WARNING(Service_AM, "(STUBBED) called");
+    IPC::RequestParser rp{ctx};
+    const float main_applet_volume_tmp = rp.Pop<float>();
+    const float library_applet_volume_tmp = rp.Pop<float>();
+
+    LOG_DEBUG(Service_AM, "called. main_applet_volume={}, library_applet_volume={}",
+              main_applet_volume_tmp, library_applet_volume_tmp);
+
+    // Ensure the volume values remain within the 0-100% range
+    main_applet_volume = std::clamp(main_applet_volume_tmp, min_allowed_volume, max_allowed_volume);
+    library_applet_volume =
+        std::clamp(library_applet_volume_tmp, min_allowed_volume, max_allowed_volume);
+
     IPC::ResponseBuilder rb{ctx, 2};
     rb.Push(RESULT_SUCCESS);
 }
 
 void IAudioController::GetMainAppletExpectedMasterVolume(Kernel::HLERequestContext& ctx) {
-    LOG_WARNING(Service_AM, "(STUBBED) called");
+    LOG_DEBUG(Service_AM, "called. main_applet_volume={}", main_applet_volume);
     IPC::ResponseBuilder rb{ctx, 3};
     rb.Push(RESULT_SUCCESS);
-    rb.Push(volume);
+    rb.Push(main_applet_volume);
 }
 
 void IAudioController::GetLibraryAppletExpectedMasterVolume(Kernel::HLERequestContext& ctx) {
-    LOG_WARNING(Service_AM, "(STUBBED) called");
+    LOG_DEBUG(Service_AM, "called. library_applet_volume={}", library_applet_volume);
     IPC::ResponseBuilder rb{ctx, 3};
     rb.Push(RESULT_SUCCESS);
-    rb.Push(volume);
+    rb.Push(library_applet_volume);
 }
 
 IDisplayController::IDisplayController() : ServiceFramework("IDisplayController") {

src/core/hle/service/am/am.h

@@ -82,7 +82,11 @@ private:
     void GetMainAppletExpectedMasterVolume(Kernel::HLERequestContext& ctx);
     void GetLibraryAppletExpectedMasterVolume(Kernel::HLERequestContext& ctx);
 
-    u32 volume{100};
+    static constexpr float min_allowed_volume = 0.0f;
+    static constexpr float max_allowed_volume = 1.0f;
+
+    float main_applet_volume{0.25f};
+    float library_applet_volume{max_allowed_volume};
 };
 
 class IDisplayController final : public ServiceFramework<IDisplayController> {