From 4d938cd31a35cd4322fe914edd568faa5391c9c2 Mon Sep 17 00:00:00 2001
From: Felix Morgner <felix.morgner@ost.ch>
Date: Mon, 6 Apr 2026 15:10:04 +0200
Subject: kernel/acpi: implement basic table discovery

---
 kapi/include/kapi/acpi.hpp             | 29 +++++++++++++++-------
 kernel/include/kernel/acpi/manager.hpp |  5 +++-
 kernel/kapi/acpi.cpp                   | 45 ++++++++++++++++++++++++++++++++++
 kernel/src/acpi/manager.cpp            | 42 +++++++++++++++++++++++++++++--
 libs/kstd/include/kstd/flat_map        | 18 ++++++++++++++
 5 files changed, 127 insertions(+), 12 deletions(-)

diff --git a/kapi/include/kapi/acpi.hpp b/kapi/include/kapi/acpi.hpp
index d5e3c87..11068d1 100644
--- a/kapi/include/kapi/acpi.hpp
+++ b/kapi/include/kapi/acpi.hpp
@@ -19,15 +19,26 @@ namespace 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;
+    [[nodiscard]] auto checksum() const noexcept -> std::uint8_t;
+    [[nodiscard]] auto creator_revision() const noexcept -> std::uint32_t;
+    [[nodiscard]] auto creator_id() const noexcept -> std::uint32_t;
+    [[nodiscard]] auto length() const noexcept -> kstd::units::bytes;
+    [[nodiscard]] auto oem_id() const noexcept -> std::string_view;
+    [[nodiscard]] auto oem_revision() const noexcept -> std::uint32_t;
+    [[nodiscard]] auto oem_table_id() const noexcept -> std::string_view;
+    [[nodiscard]] auto revision() const noexcept -> std::uint8_t;
+    [[nodiscard]] auto signature() const noexcept -> std::string_view;
+
+  private:
+    std::array<char, 4> m_signature;
+    std::uint32_t m_length;
+    std::uint8_t m_revision;
+    std::uint8_t m_checksum;
+    std::array<char, 6> m_oem_id;
+    std::array<char, 8> m_oem_table_id;
+    std::uint32_t m_oem_revision;
+    std::uint32_t m_creator_id;
+    std::uint32_t m_creator_revision;
   };
 
   //! @}
diff --git a/kernel/include/kernel/acpi/manager.hpp b/kernel/include/kernel/acpi/manager.hpp
index fc76685..437d4c8 100644
--- a/kernel/include/kernel/acpi/manager.hpp
+++ b/kernel/include/kernel/acpi/manager.hpp
@@ -3,8 +3,11 @@
 
 #include "kapi/acpi.hpp"
 
+#include <kstd/flat_map>
 #include <kstd/vector>
 
+#include <string_view>
+
 namespace kernel::acpi
 {
 
@@ -17,7 +20,7 @@ namespace kernel::acpi
   private:
     kapi::acpi::root_system_description_pointer const * m_sdp{};
     kapi::acpi::system_description_table_header const * m_rsdt{};
-    kstd::vector<kapi::acpi::system_description_table_header> m_tables{};
+    kstd::flat_map<std::string_view, kapi::acpi::system_description_table_header const *> m_tables{};
     bool m_extended{};
   };
 
diff --git a/kernel/kapi/acpi.cpp b/kernel/kapi/acpi.cpp
index 787bcff..998d7a0 100644
--- a/kernel/kapi/acpi.cpp
+++ b/kernel/kapi/acpi.cpp
@@ -65,6 +65,51 @@ namespace kapi::acpi
     return validate_checksum({reinterpret_cast<std::byte const *>(this), m_length});
   }
 
+  [[nodiscard]] auto system_description_table_header::checksum() const noexcept -> std::uint8_t
+  {
+    return m_checksum;
+  }
+
+  [[nodiscard]] auto system_description_table_header::creator_revision() const noexcept -> std::uint32_t
+  {
+    return m_creator_revision;
+  }
+
+  [[nodiscard]] auto system_description_table_header::creator_id() const noexcept -> std::uint32_t
+  {
+    return m_creator_id;
+  }
+
+  [[nodiscard]] auto system_description_table_header::length() const noexcept -> kstd::units::bytes
+  {
+    return kstd::units::bytes{m_length};
+  }
+
+  [[nodiscard]] auto system_description_table_header::oem_id() const noexcept -> std::string_view
+  {
+    return {m_oem_id.data(), m_oem_id.size()};
+  }
+
+  [[nodiscard]] auto system_description_table_header::oem_revision() const noexcept -> std::uint32_t
+  {
+    return m_oem_revision;
+  }
+
+  [[nodiscard]] auto system_description_table_header::oem_table_id() const noexcept -> std::string_view
+  {
+    return {m_oem_table_id.data(), m_oem_table_id.size()};
+  }
+
+  [[nodiscard]] auto system_description_table_header::revision() const noexcept -> std::uint8_t
+  {
+    return m_revision;
+  }
+
+  [[nodiscard]] auto system_description_table_header::signature() const noexcept -> std::string_view
+  {
+    return {m_signature.data(), m_signature.size()};
+  }
+
   auto init(root_system_description_pointer const & sdp) -> bool
   {
     auto static constinit initialized = std::atomic_flag{};
diff --git a/kernel/src/acpi/manager.cpp b/kernel/src/acpi/manager.cpp
index 6a17920..180d458 100644
--- a/kernel/src/acpi/manager.cpp
+++ b/kernel/src/acpi/manager.cpp
@@ -4,7 +4,10 @@
 #include "kapi/memory.hpp"
 #include "kapi/system.hpp"
 
+#include <kstd/print>
+
 #include <cstddef>
+#include <cstdint>
 
 namespace kernel::acpi
 {
@@ -43,12 +46,47 @@ namespace kernel::acpi
 
   auto manager::load_tables() -> bool
   {
-    if (!kapi::acpi::validate_checksum({reinterpret_cast<std::byte const *>(m_rsdt), m_rsdt->length}))
+    if (!kapi::acpi::validate_checksum({reinterpret_cast<std::byte const *>(m_rsdt), m_rsdt->length().value}))
     {
       kapi::system::panic("[OS:ACPI] Invalid RSDT checksum!");
     }
 
-    return false;
+    auto entry_size = m_extended ? sizeof(std::uint64_t) : sizeof(std::uint32_t);
+    auto entry_count = (m_rsdt->length().value - sizeof(kapi::acpi::system_description_table_header)) / entry_size;
+    auto entries_base =
+        reinterpret_cast<std::byte const *>(m_rsdt) + sizeof(kapi::acpi::system_description_table_header);
+
+    for (std::size_t i = 0; i < entry_count; ++i)
+    {
+      auto physical_table_address = kapi::memory::physical_address{};
+
+      if (m_extended)
+      {
+        auto entry = reinterpret_cast<std::uint64_t const *>(entries_base + (i * entry_size));
+        physical_table_address = kapi::memory::physical_address{*entry};
+      }
+      else
+      {
+        auto entry = reinterpret_cast<std::uint32_t const *>(entries_base + (i * entry_size));
+        physical_table_address = kapi::memory::physical_address{*entry};
+      }
+
+      auto linear_table_address = kapi::memory::hhdm_to_linear(physical_table_address);
+      auto table = static_cast<kapi::acpi::system_description_table_header const *>(linear_table_address);
+
+      if (!kapi::acpi::validate_checksum({reinterpret_cast<std::byte const *>(table), table->length().value}))
+      {
+        kstd::println(kstd::print_sink::stderr, "[OS:ACPI] Invalid table checksum!");
+      }
+      else
+      {
+        kstd::println("[OS:ACPI] Found table: {}@{:#x}/{:#x} OEM: {} Rev: {}", table->signature(), linear_table_address,
+                      physical_table_address, table->oem_id(), table->creator_revision());
+        m_tables.emplace(table->signature(), table);
+      }
+    }
+
+    return !m_tables.empty();
   }
 
 }  // namespace kernel::acpi
diff --git a/libs/kstd/include/kstd/flat_map b/libs/kstd/include/kstd/flat_map
index 6ffbbcf..3b13754 100644
--- a/libs/kstd/include/kstd/flat_map
+++ b/libs/kstd/include/kstd/flat_map
@@ -205,6 +205,24 @@ namespace kstd
       return const_reverse_iterator{cbegin()};
     }
 
+    //! Check whether this flat map is empty or not
+    [[nodiscard]] auto empty() const noexcept -> bool
+    {
+      return m_containers.keys.empty();
+    }
+
+    //! Get the number of elements in this flat map.
+    [[nodiscard]] auto size() const noexcept -> size_type
+    {
+      return m_containers.keys.size();
+    }
+
+    //! Get the maximum number of elements possible in this flat map
+    [[nodiscard]] auto max_size() const noexcept -> size_type
+    {
+      return std::min(m_containers.keys.max_size(), m_containers.values.max_size());
+    }
+
     //! Try to insert a new key-value pair into the map.
     //!
     //! @param args Arguments to use for constructing the key-value pair.
-- 
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