Kernel: Move VirtIO code into the Bus source folder

The VirtIO code handles functionality related to the VirtIO bus, so it
really should be in the Bus folder.

Kernel/Bus/VirtIO/VirtIOConsolePort.h

@@ -0,0 +1,63 @@
+/*
+ * Copyright (c) 2021, the SerenityOS developers.
+ * Copyright (c) 2021, Kyle Pereira <hey@xylepereira.me>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <Kernel/Bus/VirtIO/VirtIO.h>
+#include <Kernel/Devices/CharacterDevice.h>
+#include <Kernel/FileSystem/FileDescription.h>
+#include <Kernel/Memory/RingBuffer.h>
+
+namespace Kernel {
+
+class VirtIOConsole;
+
+#define VIRTIO_CONSOLE_F_SIZE (1 << 0)
+#define VIRTIO_CONSOLE_F_MULTIPORT (1 << 1)
+#define VIRTIO_CONSOLE_F_EMERG_WRITE (1 << 2)
+
+class VirtIOConsolePort
+    : public CharacterDevice {
+public:
+    explicit VirtIOConsolePort(unsigned port, VirtIOConsole&);
+    void handle_queue_update(Badge<VirtIOConsole>, u16 queue_index);
+
+    void set_open(Badge<VirtIOConsole>, bool state) { m_open = state; }
+    bool is_open() const { return m_open; }
+
+private:
+    constexpr static size_t RINGBUFFER_SIZE = 2 * PAGE_SIZE;
+
+    virtual StringView class_name() const override { return "VirtIOConsolePort"; }
+
+    virtual bool can_read(const FileDescription&, size_t) const override;
+    virtual KResultOr<size_t> read(FileDescription&, u64, UserOrKernelBuffer&, size_t) override;
+    virtual bool can_write(const FileDescription&, size_t) const override;
+    virtual KResultOr<size_t> write(FileDescription&, u64, const UserOrKernelBuffer&, size_t) override;
+    virtual KResultOr<NonnullRefPtr<FileDescription>> open(int options) override;
+
+    mode_t required_mode() const override { return 0666; }
+
+    String device_name() const override;
+
+    void init_receive_buffer();
+
+    static unsigned next_device_id;
+    u16 m_receive_queue {};
+    u16 m_transmit_queue {};
+
+    OwnPtr<Memory::RingBuffer> m_receive_buffer;
+    OwnPtr<Memory::RingBuffer> m_transmit_buffer;
+
+    VirtIOConsole& m_console;
+    unsigned m_port;
+
+    bool m_open { false };
+    Atomic<bool> m_receive_buffer_exhausted;
+};
+
+}