Kernel/USB: Split SysFS code into its own file

This makes it controller agnostic and allows us to access it from the
USB hub code.

The copyright says "Liav A." because git blame says he wrote this.

Kernel/Bus/USB/SysFSUSB.cpp

@@ -0,0 +1,127 @@
+/*
+ * Copyright (c) 2021, Liav A. <liavalb@hotmail.co.il>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <AK/JsonArraySerializer.h>
+#include <AK/JsonObjectSerializer.h>
+#include <Kernel/Bus/USB/SysFSUSB.h>
+#include <Kernel/KBufferBuilder.h>
+
+namespace Kernel::USB {
+
+static SysFSUSBBusDirectory* s_procfs_usb_bus_directory;
+
+SysFSUSBDeviceInformation::SysFSUSBDeviceInformation(USB::Device& device)
+    : SysFSComponent(String::number(device.address()))
+    , m_device(device)
+{
+}
+
+SysFSUSBDeviceInformation::~SysFSUSBDeviceInformation()
+{
+}
+
+KResultOr<size_t> SysFSUSBDeviceInformation::read_bytes(off_t offset, size_t count, UserOrKernelBuffer& buffer, FileDescription*) const
+{
+    KBufferBuilder builder;
+    JsonArraySerializer array { builder };
+
+    auto obj = array.add_object();
+    obj.add("usb_spec_compliance_bcd", m_device->device_descriptor().usb_spec_compliance_bcd);
+    obj.add("device_class", m_device->device_descriptor().device_class);
+    obj.add("device_sub_class", m_device->device_descriptor().device_sub_class);
+    obj.add("device_protocol", m_device->device_descriptor().device_protocol);
+    obj.add("max_packet_size", m_device->device_descriptor().max_packet_size);
+    obj.add("vendor_id", m_device->device_descriptor().vendor_id);
+    obj.add("product_id", m_device->device_descriptor().product_id);
+    obj.add("device_release_bcd", m_device->device_descriptor().device_release_bcd);
+    obj.add("manufacturer_id_descriptor_index", m_device->device_descriptor().manufacturer_id_descriptor_index);
+    obj.add("product_string_descriptor_index", m_device->device_descriptor().product_string_descriptor_index);
+    obj.add("serial_number_descriptor_index", m_device->device_descriptor().serial_number_descriptor_index);
+    obj.add("num_configurations", m_device->device_descriptor().num_configurations);
+    obj.finish();
+    array.finish();
+
+    auto data = builder.build();
+    if (!data)
+        return ENOMEM;
+
+    ssize_t nread = min(static_cast<off_t>(data->size() - offset), static_cast<off_t>(count));
+    if (!buffer.write(data->data() + offset, nread))
+        return EFAULT;
+
+    return nread;
+}
+
+KResult SysFSUSBBusDirectory::traverse_as_directory(unsigned fsid, Function<bool(FileSystem::DirectoryEntryView const&)> callback) const
+{
+    ScopedSpinLock lock(m_lock);
+    // Note: if the parent directory is null, it means something bad happened as this should not happen for the USB directory.
+    VERIFY(m_parent_directory);
+    callback({ ".", { fsid, component_index() }, 0 });
+    callback({ "..", { fsid, m_parent_directory->component_index() }, 0 });
+
+    for (auto& device_node : m_device_nodes) {
+        InodeIdentifier identifier = { fsid, device_node.component_index() };
+        callback({ device_node.name(), identifier, 0 });
+    }
+    return KSuccess;
+}
+
+RefPtr<SysFSComponent> SysFSUSBBusDirectory::lookup(StringView name)
+{
+    ScopedSpinLock lock(m_lock);
+    for (auto& device_node : m_device_nodes) {
+        if (device_node.name() == name) {
+            return device_node;
+        }
+    }
+    return {};
+}
+
+RefPtr<SysFSUSBDeviceInformation> SysFSUSBBusDirectory::device_node_for(USB::Device& device)
+{
+    RefPtr<USB::Device> checked_device = device;
+    for (auto& device_node : m_device_nodes) {
+        if (device_node.device().ptr() == checked_device.ptr())
+            return device_node;
+    }
+    return {};
+}
+
+void SysFSUSBBusDirectory::plug(USB::Device& new_device)
+{
+    ScopedSpinLock lock(m_lock);
+    auto device_node = device_node_for(new_device);
+    VERIFY(!device_node);
+    m_device_nodes.append(SysFSUSBDeviceInformation::create(new_device));
+}
+
+void SysFSUSBBusDirectory::unplug(USB::Device& deleted_device)
+{
+    ScopedSpinLock lock(m_lock);
+    auto device_node = device_node_for(deleted_device);
+    VERIFY(device_node);
+    device_node->m_list_node.remove();
+}
+
+UNMAP_AFTER_INIT SysFSUSBBusDirectory::SysFSUSBBusDirectory(SysFSBusDirectory& buses_directory)
+    : SysFSDirectory("usb"sv, buses_directory)
+{
+}
+
+UNMAP_AFTER_INIT void SysFSUSBBusDirectory::initialize()
+{
+    auto directory = adopt_ref(*new SysFSUSBBusDirectory(SysFSComponentRegistry::the().buses_directory()));
+    SysFSComponentRegistry::the().register_new_bus_directory(directory);
+    s_procfs_usb_bus_directory = directory;
+}
+
+NonnullRefPtr<SysFSUSBDeviceInformation> SysFSUSBDeviceInformation::create(USB::Device& device)
+{
+    return adopt_ref(*new SysFSUSBDeviceInformation(device));
+}
+
+}