x86_64/device_io: split port read/write features

2 files changed, 56 insertions, 46 deletions

diff --git a/arch/x86_64/include/x86_64/device_io/port_io.hpp b/arch/x86_64/include/x86_64/device_io/port_io.hpp
index 9f115eb..c3e5271 100644
--- a/arch/x86_64/include/x86_64/device_io/port_io.hpp
+++ b/arch/x86_64/include/x86_64/device_io/port_io.hpp
@@ -21,73 +21,79 @@ namespace teachos::io::x86_64
                            std::conditional_t<sizeof(ValueType) == 2, std::uint16_t, std::uint32_t>>{});
   };
 
-  //! An I/O port of a given size at a given address.
-  //!
-  //! Port I/O leverages a separate address space to communicate with devices via the memory bus, allowing for byte to
-  //! double-word sized transfers.
-  //!
-  //! @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, port_io_type ValueType>
-  struct port
+  template<typename Derived>
+  struct port_read
   {
-    //! The type of data available for reading and writing through this port.
-    using value_type = ValueType;
-
-    //! The size of the I/O port
-    constexpr auto static size = sizeof(value_type);
-
     //! Read from the I/O port.
     //!
     //! @return The data read from the I/O port.
-    auto static read() noexcept -> value_type
+    auto static read() noexcept
     {
-      auto data = value_type{};
-      asm volatile((read_code[asm_template_index])
+      auto data = typename Derived::value_type{};
+      asm volatile((code[Derived::size / 2])
                    : [data] "=m"(data)
-                   : [port] "i"(Address)
-                   : "dx", (data_register[asm_template_index]));
+                   : [port] "i"(Derived::size)
+                   : "dx", (Derived::data_register));
       return data;
     }
 
+  private:
+    //! The assembly templates used for reading from an I/O port.
+    constexpr auto static code = std::array{
+      std::string_view{"mov %[port], %%dx\nin %%dx, %%al\nmov %%al, %[data]"},
+      std::string_view{"mov %[port], %%dx\nin %%dx, %%ax\nmov %%ax, %[data]"},
+      std::string_view{"mov %[port], %%dx\nin %%dx, %%eax\nmov %%eax, %[data]"},
+    };
+  };
+
+  template<typename Derived>
+  struct port_write
+  {
     //! Write data to the I/O port.
     //!
     //! @param data The data to write to the I/O port.
-    auto static write(value_type data) noexcept -> void
+    auto static write(std::same_as<typename Derived::value_type> auto data) noexcept -> void
     {
-      asm volatile((write_code[asm_template_index])
+      asm volatile((code[Derived::size / 2])
                    :
-                   : [port] "i"(Address), [data] "im"(data)
-                   : "dx", (data_register[asm_template_index]));
+                   : [port] "i"(Derived::address), [data] "im"(data)
+                   : "dx", (Derived::data_register));
     }
 
   private:
-    //! The index into the assembly template and register arrays.
-    //!
-    //! This index is used to select the correct assembly templates for the given operation (read or write), as well as
-    //! the clobbered data register, from the relevant template arrays.
-    constexpr auto static asm_template_index = size / 2;
-
-    //! The assembly templates used for reading from an I/O port.
-    constexpr auto static read_code = std::array{
-      std::string_view{"mov %[port], %%dx\nin %%dx, %%al\nmov %%al, %[data]"},
-      std::string_view{"mov %[port], %%dx\nin %%dx, %%ax\nmov %%ax, %[data]"},
-      std::string_view{"mov %[port], %%dx\nin %%dx, %%eax\nmov %%eax, %[data]"},
-    };
-
     //! The assembly templates used for writing to an I/O port.
-    constexpr auto static write_code = std::array{
+    constexpr auto static code = std::array{
       std::string_view{"mov %[port], %%dx\nmov %%dx, %[data]\nout %%al, %%dx"},
       std::string_view{"mov %[port], %%dx\nmov %%dx, %[data]\nout %%ax, %%dx"},
       std::string_view{"mov %[port], %%dx\nmov %%dx, %[data]\nout %%eax, %%dx"},
     };
+  };
 
-    //! The registers clobbered by the I/O operation.
-    constexpr auto static data_register = std::array{
-      std::string_view{"al"},
-      std::string_view{"ax"},
-      std::string_view{"eax"},
-    };
+  //! An I/O port of a given size at a given address.
+  //!
+  //! Port I/O leverages a separate address space to communicate with devices via the memory bus, allowing for byte
+  //! to double-word sized transfers.
+  //!
+  //! @tparam Address The address (port number) of the I/O port.
+  //! @tparam Size The size (in bytes) of the I/O port.
+  //! @tparam Features The features (readable, writeable)
+  template<std::uint16_t Address, port_io_type ValueType, template<typename> typename... Features>
+    requires(sizeof...(Features) > 0)
+  struct port : Features<port<Address, ValueType, Features...>>...
+  {
+    //! The type of the data of this port.
+    using value_type = ValueType;
+
+    //! The address of this I/O port.
+    constexpr auto static address = Address;
+
+    //! The size of this I/O port.
+    constexpr auto static size = sizeof(value_type);
+
+    //! The register clobbered by the I/O operation.
+    constexpr auto static data_register = size == 1   ? std::string_view{"al"}
+                                          : size == 2 ? std::string_view{"ax"}
+                                                      : std::string_view{"eax"};
   };
 
 }  // namespace teachos::io::x86_64
diff --git a/arch/x86_64/include/x86_64/vga/crtc.hpp b/arch/x86_64/include/x86_64/vga/crtc.hpp
index b2c8028..d4b4f51 100644
--- a/arch/x86_64/include/x86_64/vga/crtc.hpp
+++ b/arch/x86_64/include/x86_64/vga/crtc.hpp
@@ -7,15 +7,19 @@
 
 namespace teachos::vga::x86_64::crtc
 {
+  namespace io = io::x86_64;
+
   /**
    * @brief The address port of the CRT Controller.
    */
-  using address = io::x86_64::port<0x3d4, std::byte>;  // NOLINT(cppcoreguidelines-avoid-magic-numbers)
+  // NOLINTNEXTLINE(cppcoreguidelines-avoid-magic-numbers)
+  using address = io::port<0x3d4, std::byte, io::port_write>;
 
   /**
    * @brief The data port of the CRT Controller.
    */
-  using data = io::x86_64::port<0x3d5, std::byte>;  // NOLINT(cppcoreguidelines-avoid-magic-numbers)
+  // NOLINTNEXTLINE(cppcoreguidelines-avoid-magic-numbers)
+  using data = io::port<0x3d5, std::byte, io::port_read, io::port_write>;
 
   namespace registers
   {