8 files changed, 169 insertions, 1 deletions
diff --git a/arch/x86_64/CMakeLists.txt b/arch/x86_64/CMakeLists.txt
index 4427e4c..83cae0b 100644
--- a/arch/x86_64/CMakeLists.txt
+++ b/arch/x86_64/CMakeLists.txt
@@ -15,6 +15,7 @@ target_sources("x86_64" PRIVATE
     "kapi/boot_modules.cpp"
     "kapi/cio.cpp"
     "kapi/cpu.cpp"
+    "kapi/devices.cpp"
     "kapi/interrupts.cpp"
     "kapi/memory.cpp"
     "kapi/system.cpp"
@@ -24,6 +25,9 @@ target_sources("x86_64" PRIVATE
     "src/cpu/interrupts.cpp"
     "src/cpu/interrupt_stubs.S"
 
+    # Bus Initialization
+    "src/bus/isa.cpp"
+
     # Low-level bootstrap
     "src/boot/boot32.S"
     "src/boot/entry64.s"
@@ -33,6 +37,9 @@ target_sources("x86_64" PRIVATE
     # Debug interfaces
     "src/debug/qemu_output.cpp"
 
+    # Devices
+    "src/devices/legacy_pit.cpp"
+
     # Memory management
     "src/memory/kernel_mapper.cpp"
     "src/memory/higher_half_mapper.cpp"
diff --git a/arch/x86_64/include/arch/bus/isa.hpp b/arch/x86_64/include/arch/bus/isa.hpp
new file mode 100644
index 0000000..5deed25
--- /dev/null
+++ b/arch/x86_64/include/arch/bus/isa.hpp
@@ -0,0 +1,18 @@
+#ifndef TEACHOS_X86_64_BUS_ISA_HPP
+#define TEACHOS_X86_64_BUS_ISA_HPP
+
+#include "kapi/devices/bus.hpp"
+
+#include <cstddef>
+
+namespace arch::bus
+{
+
+  struct isa final : public kapi::devices::bus
+  {
+    isa(std::size_t major);
+  };
+
+}  // namespace arch::bus
+
+#endif  // TEACHOS_X86_64_BUS_ISA_HPP
diff --git a/arch/x86_64/include/arch/device_io/port_io.hpp b/arch/x86_64/include/arch/device_io/port_io.hpp
index 70773dd..4c8d66a 100644
--- a/arch/x86_64/include/arch/device_io/port_io.hpp
+++ b/arch/x86_64/include/arch/device_io/port_io.hpp
@@ -102,6 +102,11 @@ namespace arch::io
                                                       : std::string_view{"eax"};
   };
 
+  auto inline wait() -> void
+  {
+    port<0x80, std::uint8_t, port_write>::write<std::uint8_t>(0);
+  }
+
 }  // namespace arch::io
 
 #endif
 \ No newline at end of file
diff --git a/arch/x86_64/include/arch/devices/legacy_pit.hpp b/arch/x86_64/include/arch/devices/legacy_pit.hpp
new file mode 100644
index 0000000..de742ae
--- /dev/null
+++ b/arch/x86_64/include/arch/devices/legacy_pit.hpp
@@ -0,0 +1,29 @@
+#ifndef TEACHOS_ARCH_X86_64_DEVICES_LEGACY_PIT_HPP
+#define TEACHOS_ARCH_X86_64_DEVICES_LEGACY_PIT_HPP
+
+#include "kapi/devices/device.hpp"
+#include "kapi/interrupts.hpp"
+
+#include <cstddef>
+#include <cstdint>
+
+namespace arch::devices
+{
+
+  struct legacy_pit : kapi::devices::device, kapi::interrupts::handler
+  {
+    legacy_pit(std::size_t major, std::uint32_t frequency_in_hz);
+
+    auto init() -> bool override;
+
+    auto handle_interrupt(std::uint32_t irq_number) -> kapi::interrupts::status override;
+
+  private:
+    std::uint32_t m_irq_number{};
+    std::uint32_t m_frequency_in_hz{};
+    std::uint64_t m_ticks{};
+  };
+
+}  // namespace arch::devices
+
+#endif
+\ No newline at end of file
diff --git a/arch/x86_64/kapi/devices.cpp b/arch/x86_64/kapi/devices.cpp
new file mode 100644
index 0000000..b15503d
--- /dev/null
+++ b/arch/x86_64/kapi/devices.cpp
@@ -0,0 +1,35 @@
+#include "kapi/devices.hpp"
+
+#include "arch/bus/isa.hpp"
+#include "arch/devices/legacy_pit.hpp"
+
+#include <kstd/memory>
+#include <kstd/print>
+
+#include <cstdint>
+#include <utility>
+
+namespace kapi::devices
+{
+
+  namespace
+  {
+    constexpr auto pit_frequency_in_hz = std::uint32_t{100u};
+  }
+
+  auto init_platform_devices() -> void
+  {
+    kstd::println("[x86_64:devices] Initializing ISA bus...");
+
+    auto isa_major_number = kapi::devices::allocate_major_number();
+    auto isa_bus = kstd::make_unique<arch::bus::isa>(isa_major_number);
+
+    auto pit_major_number = kapi::devices::allocate_major_number();
+    auto pit = kstd::make_unique<arch::devices::legacy_pit>(pit_major_number, pit_frequency_in_hz);
+    isa_bus->add_child(std::move(pit));
+
+    auto & root_bus = get_root_bus();
+    root_bus.add_child(std::move(isa_bus));
+  }
+
+}  // namespace kapi::devices
+\ No newline at end of file
diff --git a/arch/x86_64/src/bus/isa.cpp b/arch/x86_64/src/bus/isa.cpp
new file mode 100644
index 0000000..ff4ad71
--- /dev/null
+++ b/arch/x86_64/src/bus/isa.cpp
@@ -0,0 +1,14 @@
+#include "arch/bus/isa.hpp"
+
+#include "kapi/devices.hpp"
+
+#include <cstddef>
+
+namespace arch::bus
+{
+
+  isa::isa(std::size_t major)
+      : kapi::devices::bus{major, 0, "isa"}
+  {}
+
+}  // namespace arch::bus
+\ No newline at end of file
diff --git a/arch/x86_64/src/cpu/initialization.cpp b/arch/x86_64/src/cpu/initialization.cpp
index 878fa07..b808c76 100644
--- a/arch/x86_64/src/cpu/initialization.cpp
+++ b/arch/x86_64/src/cpu/initialization.cpp
@@ -139,7 +139,7 @@ namespace arch::cpu
     constexpr auto pic_cascade_address = std::uint8_t{0x04};
     constexpr auto pic_cascade_slave_identity = std::uint8_t{0x02};
     constexpr auto pic_use_8086_mode = std::uint8_t{0x01};
-    constexpr auto pic_master_mask = std::uint8_t{0x01};
+    constexpr auto pic_master_mask = std::uint8_t{0x00};
     constexpr auto pic_slave_mask = std::uint8_t{0x00};
 
     pic_master_control_port::write(pic_init_command);
diff --git a/arch/x86_64/src/devices/legacy_pit.cpp b/arch/x86_64/src/devices/legacy_pit.cpp
new file mode 100644
index 0000000..a8df3c3
--- /dev/null
+++ b/arch/x86_64/src/devices/legacy_pit.cpp
@@ -0,0 +1,60 @@
+#include "arch/devices/legacy_pit.hpp"
+
+#include "kapi/devices.hpp"
+#include "kapi/devices/device.hpp"
+#include "kapi/interrupts.hpp"
+
+#include "arch/device_io/port_io.hpp"
+
+#include <cstddef>
+#include <cstdint>
+
+namespace arch::devices
+{
+
+  namespace
+  {
+    using command_port = io::port<0x43, std::uint8_t, io::port_write>;
+    using channel_0_port = io::port<0x40, std::uint8_t, io::port_write>;
+    using channel_1_port = io::port<0x41, std::uint8_t, io::port_write>;
+    using channel_2_port = io::port<0x42, std::uint8_t, io::port_write>;
+
+    constexpr auto base_frequency = 1'193'182u;
+    constexpr auto square_wave_mode = 0x36;
+  }  // namespace
+
+  legacy_pit::legacy_pit(std::size_t major, std::uint32_t frequency_in_hz)
+      : kapi::devices::device{major, 0, "legacy_pit"}
+      , m_irq_number{0}
+      , m_frequency_in_hz{frequency_in_hz}
+  {}
+
+  auto legacy_pit::init() -> bool
+  {
+    auto divisor = static_cast<std::uint16_t>(base_frequency / m_frequency_in_hz);
+
+    kapi::interrupts::register_handler(m_irq_number, *this);
+
+    command_port::write<std::uint8_t>(square_wave_mode);
+    io::wait();
+    channel_0_port::write<std::uint8_t>(divisor & 0xff);
+    io::wait();
+    channel_0_port::write<std::uint8_t>(divisor >> 8 & 0xff);
+    io::wait();
+
+    return true;
+  }
+
+  auto legacy_pit::handle_interrupt(std::uint32_t irq_number) -> kapi::interrupts::status
+  {
+    if (irq_number != m_irq_number)
+    {
+      return kapi::interrupts::status::unhandled;
+    }
+
+    ++m_ticks;
+
+    return kapi::interrupts::status::handled;
+  }
+
+}  // namespace arch::devices
+\ No newline at end of file