Kernel/USB: Get all interface descriptors on enumeration

This creates all interfaces when the device is enumerated, with a link
to the configuration that it is a part of. As such, a new class,
`USBInterface` has been introduced to express this state.

Kernel/Bus/USB/USBConfiguration.cpp

@@ -0,0 +1,77 @@
+/*
+ * Copyright (c) 2022, Jesse Buhagiar <jesse.buhagiar@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <AK/FixedArray.h>
+#include <Kernel/Bus/USB/USBClasses.h>
+#include <Kernel/Bus/USB/USBConfiguration.h>
+#include <Kernel/Bus/USB/USBInterface.h>
+#include <Kernel/Bus/USB/USBRequest.h>
+
+namespace Kernel::USB {
+
+ErrorOr<void> USBConfiguration::get_interfaces()
+{
+    auto descriptor_hierarchy_buffer = TRY(FixedArray<u8>::try_create(m_descriptor.total_length)); // Buffer for us to store the entire hierarchy into
+
+    // The USB spec is a little bit janky here... Interface and Endpoint descriptors aren't fetched
+    // through a `GET_DESCRIPTOR` request to the device. Instead, the _entire_ hierarchy is returned
+    // to us in one go.
+    auto transfer_length = TRY(m_device.control_transfer(USB_REQUEST_TRANSFER_DIRECTION_DEVICE_TO_HOST, USB_REQUEST_GET_DESCRIPTOR, (DESCRIPTOR_TYPE_CONFIGURATION << 8), 0, m_descriptor.total_length, descriptor_hierarchy_buffer.data()));
+
+    // FIXME: Why does transfer length return the actual size +8 bytes?
+    if (transfer_length < m_descriptor.total_length)
+        return EIO;
+
+    u8* interface_descriptors_base = descriptor_hierarchy_buffer.data() + sizeof(USBConfigurationDescriptor);
+    USBInterfaceDescriptor* interface_descriptor = reinterpret_cast<USBInterfaceDescriptor*>(interface_descriptors_base);
+    Vector<USBEndpointDescriptor> endpoint_descriptors;
+    for (auto interface = 0u; interface < m_descriptor.number_of_interfaces; interface++) {
+        endpoint_descriptors.ensure_capacity(interface_descriptor->number_of_endpoints);
+
+        if constexpr (USB_DEBUG) {
+            dbgln("Interface Descriptor {}", interface);
+            dbgln("interface_id: {:02x}", interface_descriptor->interface_id);
+            dbgln("alternate_setting: {:02x}", interface_descriptor->alternate_setting);
+            dbgln("number_of_endpoints: {:02x}", interface_descriptor->number_of_endpoints);
+            dbgln("interface_class_code: {:02x}", interface_descriptor->interface_class_code);
+            dbgln("interface_sub_class_code: {:02x}", interface_descriptor->interface_sub_class_code);
+            dbgln("interface_protocol: {:02x}", interface_descriptor->interface_protocol);
+            dbgln("interface_string_descriptor_index: {}", interface_descriptor->interface_string_descriptor_index);
+        }
+
+        // Get all the endpoint descriptors
+        for (auto endpoint = 0u; endpoint < interface_descriptor->number_of_endpoints; endpoint++) {
+            u8* raw_endpoint_descriptor_offset = interface_descriptors_base + sizeof(USBInterfaceDescriptor) + (endpoint * sizeof(USBEndpointDescriptor));
+
+            // FIXME: It looks like HID descriptors come BEFORE the endpoint descriptors for a HID device, so we should load
+            // these too eventually.
+            // See here: https://www.usb.org/defined-class-codes
+            if (interface_descriptor->interface_class_code == USB_CLASS_HID)
+                raw_endpoint_descriptor_offset += sizeof(USBHIDDescriptor); // Skip the HID descriptor (this was worked out via buffer inspection)
+
+            USBEndpointDescriptor endpoint_descriptor;
+            memcpy(&endpoint_descriptor, raw_endpoint_descriptor_offset, sizeof(USBEndpointDescriptor));
+
+            if constexpr (USB_DEBUG) {
+                dbgln("Endpoint Descriptor {}", endpoint);
+                dbgln("Endpoint Address: {}", endpoint_descriptor.endpoint_address);
+                dbgln("Endpoint Attribute Bitmap: {:08b}", endpoint_descriptor.endpoint_attributes_bitmap);
+                dbgln("Endpoint Maximum Packet Size: {}", endpoint_descriptor.max_packet_size);
+                dbgln("Endpoint Poll Interval (in frames): {}", endpoint_descriptor.poll_interval_in_frames);
+            }
+
+            endpoint_descriptors.append(endpoint_descriptor);
+        }
+
+        USBInterface device_interface(*this, *interface_descriptor, endpoint_descriptors);
+        m_interfaces.append(device_interface);
+        interface_descriptor += interface_descriptor->number_of_endpoints * sizeof(USBEndpointDescriptor);
+    }
+
+    return {};
+}
+
+}