Kernel: Move a bunch of generic devices code into new subdirectory

Kernel/Devices/Generic/NullDevice.cpp

@@ -0,0 +1,44 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <AK/Singleton.h>
+#include <Kernel/Devices/DeviceManagement.h>
+#include <Kernel/Devices/Generic/NullDevice.h>
+#include <Kernel/Sections.h>
+
+namespace Kernel {
+
+UNMAP_AFTER_INIT NonnullLockRefPtr<NullDevice> NullDevice::must_initialize()
+{
+    auto null_device_or_error = DeviceManagement::try_create_device<NullDevice>();
+    // FIXME: Find a way to propagate errors
+    VERIFY(!null_device_or_error.is_error());
+    return null_device_or_error.release_value();
+}
+
+UNMAP_AFTER_INIT NullDevice::NullDevice()
+    : CharacterDevice(1, 3)
+{
+}
+
+UNMAP_AFTER_INIT NullDevice::~NullDevice() = default;
+
+bool NullDevice::can_read(OpenFileDescription const&, u64) const
+{
+    return true;
+}
+
+ErrorOr<size_t> NullDevice::read(OpenFileDescription&, u64, UserOrKernelBuffer&, size_t)
+{
+    return 0;
+}
+
+ErrorOr<size_t> NullDevice::write(OpenFileDescription&, u64, UserOrKernelBuffer const&, size_t buffer_size)
+{
+    return buffer_size;
+}
+
+}