diff --git a/src/ipmiblob/internal/sys_interface.hpp b/src/ipmiblob/internal/sys_interface.hpp
new file mode 100644
index 0000000..ffd32b7
--- /dev/null
+++ b/src/ipmiblob/internal/sys_interface.hpp
@@ -0,0 +1,42 @@
+#pragma once
+
+/* NOTE: IIRC, wak@ is working on exposing some of this in stdplus, so we can
+ * transition when that's ready.
+ *
+ * Copied some from gpioplus to enable unit-testing of lpc nuvoton and later
+ * other pieces.
+ */
+
+#include <poll.h>
+#include <sys/mman.h>
+
+#include <cinttypes>
+#include <cstddef>
+
+namespace ipmiblob
+{
+namespace internal
+{
+
+/**
+ * @class Sys
+ * @brief Overridable direct syscall interface
+ */
+class Sys
+{
+  public:
+    virtual ~Sys() = default;
+
+    virtual int open(const char* pathname, int flags) const = 0;
+    virtual int read(int fd, void* buf, std::size_t count) const = 0;
+    virtual int close(int fd) const = 0;
+    virtual void* mmap(void* addr, std::size_t length, int prot, int flags,
+                       int fd, off_t offset) const = 0;
+    virtual int munmap(void* addr, std::size_t length) const = 0;
+    virtual int getpagesize() const = 0;
+    virtual int ioctl(int fd, unsigned long request, void* param) const = 0;
+    virtual int poll(struct pollfd* fds, nfds_t nfds, int timeout) const = 0;
+};
+
+} // namespace internal
+} // namespace ipmiblob