Kernel: Add a new abstraction for I/O mapped registers

AK/Concepts.h

@@ -38,6 +38,9 @@ concept Enum = IsEnum<T>;
 template<typename T, typename U>
 concept SameAs = IsSame<T, U>;
 
+template<typename T, typename U>
+concept SameAsIgnoringCVReference = IsSameIgnoringCV<RemoveReference<T>, RemoveReference<U>>;
+
 template<class From, class To>
 concept ConvertibleTo = IsConvertible<From, To>;
 
@@ -182,6 +185,7 @@ using AK::Concepts::IteratorPairWith;
 using AK::Concepts::OneOf;
 using AK::Concepts::OneOfIgnoringCV;
 using AK::Concepts::SameAs;
+using AK::Concepts::SameAsIgnoringCVReference;
 using AK::Concepts::Signed;
 using AK::Concepts::SpecializationOf;
 using AK::Concepts::Unsigned;

Kernel/Library/IORegister.h

@@ -0,0 +1,115 @@
+/*
+ * Copyright (c) 2024, Leon Albrecht <[email protected]>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Concepts.h>
+#include <AK/Types.h>
+#include <Kernel/Library/IOWindow.h>
+
+namespace Kernel {
+
+enum IOSize {
+    Byte,
+    Word,
+    DWord,
+};
+
+template<typename T>
+consteval IOSize io_size_for()
+{
+    if constexpr (sizeof(T) == 1)
+        return IOSize::Byte;
+    else if constexpr (sizeof(T) == 2)
+        return IOSize::Word;
+    else if constexpr (sizeof(T) == 4)
+        return IOSize::DWord;
+    else
+        static_assert(false, "Invalid IO size");
+}
+
+template<Enum E, E L, typename T>
+struct IOReg {
+    static constexpr E Location = L;
+    static constexpr IOSize Size = io_size_for<T>();
+    using Type = T;
+};
+
+template<typename T, typename E>
+concept RegisterEntry = IsEnum<E> && requires {
+    typename T::Type;
+    { T::Location } -> SameAsIgnoringCVReference<E>;
+    { T::Size } -> SameAsIgnoringCVReference<IOSize>;
+};
+
+template<Enum E, RegisterEntry<E>... Entries>
+class IORegister {
+    template<E Reg, RegisterEntry<E> First, RegisterEntry<E>... Rest>
+    static consteval auto find_entry(First, Rest...)
+    {
+        if constexpr (First::Location == Reg)
+            return First();
+        else if constexpr (sizeof...(Rest) > 0)
+            return find_entry<Reg>(Rest()...);
+        else
+            static_assert(false, "Register not found");
+    }
+
+public:
+    explicit IORegister(NonnullOwnPtr<IOWindow> window)
+        : m_window(move(window))
+    {
+    }
+
+    template<E Reg, typename Entry = decltype(find_entry<Reg>(declval<Entries>()...))>
+    requires(Entry::Size == IOSize::Byte)
+    auto read()
+    {
+        return bit_cast<typename Entry::Type>(m_window->read8(static_cast<u64>(Reg)));
+    }
+
+    template<E Reg, typename Entry = decltype(find_entry<Reg>(declval<Entries>()...))>
+    requires(Entry::Size == IOSize::Word)
+    auto read()
+    {
+        return bit_cast<typename Entry::Type>(m_window->read16(static_cast<u64>(Reg)));
+    }
+
+    template<E Reg, typename Entry = decltype(find_entry<Reg>(declval<Entries>()...))>
+    requires(Entry::Size == IOSize::DWord)
+    auto read()
+    {
+        return bit_cast<typename Entry::Type>(m_window->read32(static_cast<u64>(Reg)));
+    }
+
+    template<E Reg, typename Entry = decltype(find_entry<Reg>(declval<Entries>()...))>
+    requires(Entry::Size == IOSize::Byte)
+    void write(Entry::Type value)
+    {
+        m_window->write8(static_cast<u64>(Reg), bit_cast<u8>(value));
+    }
+
+    template<E Reg, typename Entry = decltype(find_entry<Reg>(declval<Entries>()...))>
+    requires(Entry::Size == IOSize::Word)
+    void write(Entry::Type value)
+    {
+        m_window->write16(static_cast<u64>(Reg), bit_cast<u16>(value));
+    }
+
+    template<E Reg, typename Entry = decltype(find_entry<Reg>(declval<Entries>()...))>
+    requires(Entry::Size == IOSize::DWord)
+    void write(Entry::Type value)
+    {
+        m_window->write32(static_cast<u64>(Reg), bit_cast<u32>(value));
+    }
+
+    IOWindow& window() { return *m_window; }
+
+private:
+    NonnullOwnPtr<IOWindow> m_window;
+};
+
+}