From bd585306e31889ee4fce60abb79bc3b3a58e2b84 Mon Sep 17 00:00:00 2001
From: Felix Morgner <felix.morgner@ost.ch>
Date: Mon, 6 Apr 2026 13:11:15 +0200
Subject: kapi: add basic ACPI support

---
 kapi/CMakeLists.txt        |  8 ++++--
 kapi/include/kapi/acpi.hpp | 64 +++++++++++++++++++++++++++++++++++++++++++
 kapi/src/acpi.cpp          | 68 ++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 137 insertions(+), 3 deletions(-)
 create mode 100644 kapi/include/kapi/acpi.hpp
 create mode 100644 kapi/src/acpi.cpp

(limited to 'kapi')

diff --git a/kapi/CMakeLists.txt b/kapi/CMakeLists.txt
index c9aa23f..eeda158 100644
--- a/kapi/CMakeLists.txt
+++ b/kapi/CMakeLists.txt
@@ -1,4 +1,6 @@
-add_library("kapi" INTERFACE)
+add_library("kapi" STATIC
+    "src/acpi.cpp"
+)
 add_library("os::kapi" ALIAS "kapi")
 
 file(GLOB_RECURSE KAPI_HEADERS RELATIVE ${CMAKE_CURRENT_SOURCE_DIR} "include/**.hpp")
@@ -10,11 +12,11 @@ target_sources("kapi" PUBLIC
     ${KAPI_HEADERS}
 )
 
-target_include_directories("kapi" INTERFACE
+target_include_directories("kapi" PUBLIC
     "include"
 )
 
-target_link_libraries("kapi" INTERFACE
+target_link_libraries("kapi" PUBLIC
     "libs::kstd"
 
     "gcc"
diff --git a/kapi/include/kapi/acpi.hpp b/kapi/include/kapi/acpi.hpp
new file mode 100644
index 0000000..20e5e77
--- /dev/null
+++ b/kapi/include/kapi/acpi.hpp
@@ -0,0 +1,64 @@
+#ifndef TEACHOS_KAPI_ACPI_HPP
+#define TEACHOS_KAPI_ACPI_HPP
+
+#include "kapi/memory.hpp"
+#include <kstd/units>
+
+#include <array>
+#include <cstddef>
+#include <cstdint>
+#include <string_view>
+
+namespace kapi::acpi
+{
+
+  //! @addtogroup kapi-acpi-api-defined
+  //! @{
+
+  struct [[gnu::packed]] root_system_description_pointer
+  {
+    [[nodiscard]] auto oem_id() const noexcept -> std::string_view;
+    [[nodiscard]] auto revision() const noexcept -> std::uint8_t;
+    [[nodiscard]] auto signature() const noexcept -> std::string_view;
+    [[nodiscard]] auto table_address() const noexcept -> memory::physical_address;
+    [[nodiscard]] auto validate() const noexcept -> bool;
+
+  private:
+    std::array<char, 8> m_signature;
+    [[maybe_unused]] std::uint8_t m_checksum;
+    std::array<char, 6> m_oem_id;
+    std::uint8_t m_revision;
+    std::array<std::byte, 4> m_rsdt_address;
+  };
+
+  struct [[gnu::packed]] extended_system_description_pointer : root_system_description_pointer
+  {
+    [[nodiscard]] auto length() const noexcept -> kstd::units::bytes;
+    [[nodiscard]] auto table_address() const noexcept -> memory::physical_address;
+    [[nodiscard]] auto validate() const noexcept -> bool;
+
+  private:
+    std::uint32_t m_length;
+    std::array<std::byte, 8> m_xsdt_address;
+    [[maybe_unused]] std::uint8_t m_extended_checksum;
+    [[maybe_unused]] std::array<std::byte, 3> m_reserved;
+  };
+
+  //! @}
+
+  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;
+  };
+
+}  // namespace kapi::acpi
+
+#endif
diff --git a/kapi/src/acpi.cpp b/kapi/src/acpi.cpp
new file mode 100644
index 0000000..aa0066d
--- /dev/null
+++ b/kapi/src/acpi.cpp
@@ -0,0 +1,68 @@
+#include "kapi/acpi.hpp"
+
+#include "kapi/memory.hpp"
+
+#include <kstd/units>
+
+#include <algorithm>
+#include <bit>
+#include <cstddef>
+#include <cstdint>
+#include <span>
+#include <string_view>
+
+namespace kapi::acpi
+{
+
+  namespace
+  {
+    constexpr auto validate_checksum(std::span<std::byte const> data) -> bool
+    {
+      auto sum = std::ranges::fold_left(
+          data, std::uint8_t{}, [](std::uint8_t acc, auto byte) { return static_cast<std::uint8_t>(byte) + acc; });
+      return sum == 0;
+    }
+  }  // namespace
+
+  auto root_system_description_pointer::oem_id() const noexcept -> std::string_view
+  {
+    return {m_oem_id.data(), m_oem_id.size()};
+  }
+
+  auto root_system_description_pointer::revision() const noexcept -> std::uint8_t
+  {
+    return m_revision;
+  }
+
+  auto root_system_description_pointer::signature() const noexcept -> std::string_view
+  {
+    return {m_signature.data(), m_signature.size()};
+  }
+
+  auto root_system_description_pointer::table_address() const noexcept -> memory::physical_address
+  {
+    auto raw = std::bit_cast<std::uint32_t>(m_rsdt_address);
+    return memory::physical_address{static_cast<std::uintptr_t>(raw)};
+  }
+
+  auto root_system_description_pointer::validate() const noexcept -> bool
+  {
+    return validate_checksum({reinterpret_cast<std::byte const *>(this), sizeof(root_system_description_pointer)});
+  }
+
+  auto extended_system_description_pointer::length() const noexcept -> kstd::units::bytes
+  {
+    return kstd::units::bytes{m_length};
+  }
+
+  auto extended_system_description_pointer::table_address() const noexcept -> memory::physical_address
+  {
+    return memory::physical_address{std::bit_cast<std::uintptr_t>(m_xsdt_address)};
+  }
+
+  auto extended_system_description_pointer::validate() const noexcept -> bool
+  {
+    return validate_checksum({reinterpret_cast<std::byte const *>(this), m_length});
+  }
+
+};  // namespace kapi::acpi
-- 
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