From 18863e0f3db23441c0213745ad6de3722fd4c845 Mon Sep 17 00:00:00 2001
From: Felix Morgner <felix.morgner@ost.ch>
Date: Wed, 11 Oct 2023 20:16:27 +0200
Subject: x86_64: io: implement simple port I/O operations

---
 source/arch/x86_64/include/arch/io/port_io.hpp | 131 +++++++++++++++++++++++++
 1 file changed, 131 insertions(+)
 create mode 100644 source/arch/x86_64/include/arch/io/port_io.hpp

diff --git a/source/arch/x86_64/include/arch/io/port_io.hpp b/source/arch/x86_64/include/arch/io/port_io.hpp
new file mode 100644
index 0000000..736893c
--- /dev/null
+++ b/source/arch/x86_64/include/arch/io/port_io.hpp
@@ -0,0 +1,131 @@
+#ifndef TEACHOS_ARCH_X86_64_IO_PORT_IO_HPP
+#define TEACHOS_ARCH_X86_64_IO_PORT_IO_HPP
+
+#include <concepts>
+#include <cstddef>
+#include <cstdint>
+#include <type_traits>
+
+namespace teachos::arch::io
+{
+
+  /**
+   * @brief An I/O port of a given size at a given address.
+   *
+   * @tparam Address The address (port number) of the I/O port.
+   * @tparam Size The size (in bytes) of the I/O port.
+   */
+  template<std::uint16_t Address, std::size_t Size>
+  struct port
+  {
+    static_assert(Size == 1 || Size == 2 || Size == 4, "A port must be either 1, 2, or 4 bytes in size");
+
+    using io_type =
+        std::conditional_t<Size == 1, std::byte, std::conditional_t<Size == 2, std::uint16_t, std::uint32_t>>;
+
+    /**
+     * @brief Write a byte to the I/O port.
+     *
+     * @param data The data to write to the I/O port.
+     */
+    auto static write(io_type data) -> void
+      requires(Size == 1)
+    {
+      asm volatile("mov %[port], %%dx\n"
+                   "mov %[data], %%al\n"
+                   "out %%al, %%dx\n"
+                   :
+                   : [port] "i"(Address), [data] "im"(data)
+                   : "dx", "al");
+    }
+
+    /**
+     * @brief Write a word to the I/O port.
+     *
+     * @param data The data to write to the I/O port.
+     */
+    auto static write(io_type data) -> void
+      requires(Size == 2)
+    {
+      asm volatile("mov %[port], %%dx\n"
+                   "mov %[data], %%ax\n"
+                   "out %%ax, %%dx\n"
+                   :
+                   : [port] "i"(Address), [data] "im"(data)
+                   : "dx", "ax");
+    }
+
+    /**
+     * @brief Write a double-word to the I/O port.
+     *
+     * @param data The data to write to the I/O port.
+     */
+    auto static write(io_type data) -> void
+      requires(Size == 4)
+    {
+      asm volatile("mov %[port], %%dx\n"
+                   "mov %[data], %%eax\n"
+                   "out %%eax, %%dx\n"
+                   :
+                   : [port] "i"(Address), [data] "im"(data)
+                   : "dx", "eax");
+    }
+
+    /**
+     * @brief Read a byte from the I/O port.
+     *
+     * @return The data read from the I/O port.
+     */
+    auto static read() -> io_type
+      requires(Size == 1)
+    {
+      auto data = io_type{};
+      asm volatile("mov %[port], %%dx\n"
+                   "in %%dx, %%al\n"
+                   "mov %%al, %[data]\n"
+                   : [data] "=m"(data)
+                   : [port] "i"(Address)
+                   : "dx", "al");
+      return data;
+    }
+
+    /**
+     * @brief Read a word from the I/O port.
+     *
+     * @return The data read from the I/O port.
+     */
+    auto static read() -> io_type
+      requires(Size == 2)
+    {
+      auto data = io_type{};
+      asm volatile("mov %[port], %%dx\n"
+                   "in %%dx, %%ax\n"
+                   "mov %%ax, %[data]\n"
+                   : [data] "=m"(data)
+                   : [port] "i"(Address)
+                   : "dx", "ax");
+      return data;
+    }
+
+    /**
+     * @brief Read a double-word from the I/O port.
+     *
+     * @return The data read from the I/O port.
+     */
+    auto static read() -> io_type
+      requires(Size == 4)
+    {
+      auto data = io_type{};
+      asm volatile("mov %[port], %%dx\n"
+                   "in %%dx, %%eax\n"
+                   "mov %%eax, %[data]\n"
+                   : [data] "=m"(data)
+                   : [port] "i"(Address)
+                   : "dx", "eax");
+      return data;
+    }
+  };
+
+}  // namespace teachos::arch::io
+
+#endif
\ No newline at end of file
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