2 files changed, 43 insertions, 13 deletions
diff --git a/kapi/include/kapi/acpi.hpp b/kapi/include/kapi/acpi.hpp
index 1068921..d5e3c87 100644
--- a/kapi/include/kapi/acpi.hpp
+++ b/kapi/include/kapi/acpi.hpp
@@ -2,16 +2,36 @@
 #define TEACHOS_KAPI_ACPI_HPP
 
 #include "kapi/memory.hpp"
+
 #include <kstd/units>
 
 #include <array>
 #include <cstddef>
 #include <cstdint>
+#include <span>
 #include <string_view>
 
 namespace kapi::acpi
 {
 
+  //! @addtogroup kapi-acpi
+  //! @{
+
+  struct [[gnu::packed]] system_description_table_header
+  {
+    std::array<char, 4> signature;
+    std::uint32_t length;
+    std::uint8_t revision;
+    std::uint8_t checksum;
+    std::array<char, 6> oem_id;
+    std::array<char, 8> oem_table_id;
+    std::uint32_t oem_revision;
+    std::uint32_t creator_id;
+    std::uint32_t create_revision;
+  };
+
+  //! @}
+
   //! @addtogroup kapi-acpi-kernel-defined
   //! @{
 
@@ -44,20 +64,18 @@ namespace kapi::acpi
     [[maybe_unused]] std::array<std::byte, 3> m_reserved;
   };
 
-  //! @}
+  //! Initialize the ACPI subsystem and discover the available tables.
+  //!
+  //! @return true iff. a valid system description tabled was found, false otherwise.
+  auto init(root_system_description_pointer const & sdp) -> bool;
 
-  struct [[gnu::packed]] system_description_table_header
-  {
-    std::array<char, 4> signature;
-    std::uint32_t length;
-    std::uint8_t revision;
-    std::uint8_t checksum;
-    std::array<char, 6> oem_id;
-    std::array<char, 8> oem_table_id;
-    std::uint32_t oem_revision;
-    std::uint32_t creator_id;
-    std::uint32_t create_revision;
-  };
+  //! Validate and ACPI entity checksum.
+  //!
+  //! @param data The data to validate the checksum of.
+  //! @return true iff. the checksum is valid, false otherwise.
+  auto validate_checksum(std::span<std::byte const> data) -> bool;
+
+  //! @}
 
 }  // namespace kapi::acpi
 
diff --git a/kapi/include/kapi/memory/layout.hpp b/kapi/include/kapi/memory/layout.hpp
index 157f41e..26b48d8 100644
--- a/kapi/include/kapi/memory/layout.hpp
+++ b/kapi/include/kapi/memory/layout.hpp
@@ -37,6 +37,18 @@ namespace kapi::memory
   //! The linear base address of the loaded kernel image.
   constexpr auto kernel_base = linear_address{0xffff'ffff'8000'0000uz};
 
+  //! Convert a physical address to a linear address using the higher-half direct map.
+  constexpr auto hhdm_to_linear(physical_address address) -> linear_address
+  {
+    return linear_address{address.raw() + higher_half_direct_map_base.raw()};
+  }
+
+  //! Convert a linear address in the higher-half direct map to a physical address.
+  constexpr auto hhdm_to_physical(linear_address address) -> physical_address
+  {
+    return physical_address{address.raw() - higher_half_direct_map_base.raw()};
+  }
+
 }  // namespace kapi::memory
 
 #endif
 \ No newline at end of file