Kernel/SysFS: Rename Devices code folder => DeviceIdentifiers

This folder in the SysFS code represents everything related to /sys/dev,
which is a directory meant to be a convenient interface to track all IDs
of all block and character devices (ID = major:minor numbers).

Kernel/FileSystem/SysFS/Subsystems/DeviceIdentifiers/BlockDevicesDirectory.cpp

@@ -0,0 +1,51 @@
+/*
+ * Copyright (c) 2022, Liav A. <liavalb@hotmail.co.il>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <Kernel/FileSystem/SysFS/Registry.h>
+#include <Kernel/FileSystem/SysFS/Subsystems/DeviceIdentifiers/BlockDevicesDirectory.h>
+#include <Kernel/Sections.h>
+
+namespace Kernel {
+
+NonnullRefPtr<SysFSBlockDevicesDirectory> SysFSBlockDevicesDirectory::must_create(SysFSDeviceIdentifiersDirectory const& devices_directory)
+{
+    return adopt_ref_if_nonnull(new SysFSBlockDevicesDirectory(devices_directory)).release_nonnull();
+}
+SysFSBlockDevicesDirectory::SysFSBlockDevicesDirectory(SysFSDeviceIdentifiersDirectory const& devices_directory)
+    : SysFSDirectory(devices_directory)
+{
+}
+
+ErrorOr<void> SysFSBlockDevicesDirectory::traverse_as_directory(FileSystemID fsid, Function<ErrorOr<void>(FileSystem::DirectoryEntryView const&)> callback) const
+{
+    VERIFY(m_parent_directory);
+    TRY(callback({ "."sv, { fsid, component_index() }, 0 }));
+    TRY(callback({ ".."sv, { fsid, m_parent_directory->component_index() }, 0 }));
+
+    return SysFSComponentRegistry::the().devices_list().with_exclusive([&](auto& list) -> ErrorOr<void> {
+        for (auto& exposed_device : list) {
+            if (!exposed_device.is_block_device())
+                continue;
+            TRY(callback({ exposed_device.name(), { fsid, exposed_device.component_index() }, 0 }));
+        }
+        return {};
+    });
+}
+
+RefPtr<SysFSComponent> SysFSBlockDevicesDirectory::lookup(StringView name)
+{
+    return SysFSComponentRegistry::the().devices_list().with_exclusive([&](auto& list) -> RefPtr<SysFSComponent> {
+        for (auto& exposed_device : list) {
+            if (!exposed_device.is_block_device())
+                continue;
+            if (exposed_device.name() == name)
+                return exposed_device;
+        }
+        return nullptr;
+    });
+}
+
+}