diff --git a/pci_handler.hpp b/pci_handler.hpp
index f99a811..f3ae798 100644
--- a/pci_handler.hpp
+++ b/pci_handler.hpp
@@ -24,10 +24,10 @@
 class PciDataHandler : public DataInterface
 {
   public:
-    PciDataHandler(std::uint32_t regionAddress,
+    PciDataHandler(std::uint32_t regionAddress, std::size_t regionSize,
                    const internal::Sys* sys = &internal::sys_impl) :
         regionAddress(regionAddress),
-        sys(sys){};
+        memoryRegionSize(regionSize), sys(sys){};
 
     bool open() override;
     bool close() override;
@@ -37,7 +37,11 @@
 
   private:
     std::uint32_t regionAddress;
+    std::uint32_t memoryRegionSize;
     const internal::Sys* sys;
+
+    int mappedFd = -1;
+    std::uint8_t* mapped = nullptr;
     static const std::string p2aControlPath;
 };