SaveData: Added some documentation to FormatSaveData

We still don't know what the other parameters do, but they appear to be very similar to those of FormatThisUserSaveData.
Most likely FormatThisUserSaveData is just an alias for FormatSaveData with LowPathType Empty

src/core/hle/service/fs/fs_user.cpp

@@ -397,16 +397,43 @@ static void IsSdmcDetected(Service::Interface* self) {
 }
 
 /**
- * FS_User::FormatSaveData service function
+ * FS_User::FormatSaveData service function, 
+ * formats the SaveData specified by the input path.
  *  Inputs:
+ *      1  : Archive ID
+ *      2  : Archive low path type
+ *      3  : Archive low path size
+ *      10 : (LowPathSize << 14) | 2
+ *      11 : Archive low path
  *  Outputs:
  *      1 : Result of function, 0 on success, otherwise error code
  */
 static void FormatSaveData(Service::Interface* self) {
+    // TODO(Subv): Find out what the other inputs and outputs of this function are
     u32* cmd_buff = Kernel::GetCommandBuffer();
     LOG_DEBUG(Service_FS, "(STUBBED)");
 
-    // TODO(Subv): Find out what the inputs and outputs of this function are
+    auto archive_id = static_cast<FS::ArchiveIdCode>(cmd_buff[1]);
+    auto archivename_type = static_cast<FileSys::LowPathType>(cmd_buff[2]);
+    u32 archivename_size = cmd_buff[3];
+    u32 archivename_ptr = cmd_buff[11];
+    FileSys::Path archive_path(archivename_type, archivename_size, archivename_ptr);
+
+    LOG_DEBUG(Service_FS, "archive_path=%s", archive_path.DebugStr().c_str());
+
+    if (archive_id != FS::ArchiveIdCode::SaveData) {
+        // TODO(Subv): What should happen if somebody attempts to format a different archive?
+        LOG_ERROR(Service_FS, "tried to format an archive different than SaveData, %u", cmd_buff[1]);
+        cmd_buff[1] = UnimplementedFunction(ErrorModule::FS).raw;
+        return;
+    }
+
+    if (archive_path.GetType() != FileSys::LowPathType::Empty) {
+        // TODO(Subv): Implement formatting the SaveData of other games
+        LOG_ERROR(Service_FS, "archive LowPath type other than empty is currently unsupported");
+        cmd_buff[1] = UnimplementedFunction(ErrorModule::FS).raw;
+        return;
+    }
 
     cmd_buff[1] = FormatSaveData().raw;
 }