Kernel/USB: Fetch configuration descriptors on enumeration

This also introduces a new class, `USBConfiguration` that stores a
configuration. The device, when instructed, sets this configuration and
holds a pointer to it so we have a record of what configuration is
currently active.

Kernel/Bus/USB/USBConfiguration.h

@@ -0,0 +1,38 @@
+/*
+ * Copyright (c) 2022, Jesse Buhagiar <jesse.buhagiar@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Vector.h>
+#include <Kernel/Bus/USB/USBDescriptors.h>
+#include <Kernel/Bus/USB/USBDevice.h>
+
+namespace Kernel::USB {
+
+class Device;
+
+class USBConfiguration {
+public:
+    USBConfiguration() = delete;
+    USBConfiguration(Device& device, USBConfigurationDescriptor const configuration_descriptor)
+        : m_device(device)
+        , m_descriptor(configuration_descriptor)
+    {
+    }
+
+    Device const& device() const { return m_device; }
+
+    u8 interface_count() const { return m_descriptor.number_of_interfaces; }
+    u8 configuration_id() const { return m_descriptor.configuration_value; }
+    u8 attributes() const { return m_descriptor.attributes_bitmap; }
+    u16 max_power_ma() const { return m_descriptor.max_power_in_ma * 2u; } // Note: "Power" is used incorrectly here, however it's what it's called in the descriptor/documentation
+
+private:
+    Device& m_device;                  // Reference to the device linked to this configuration
+    USBConfigurationDescriptor m_descriptor; // Descriptor that backs this configuration
+};
+
+}

Kernel/Bus/USB/USBDevice.cpp

@@ -115,6 +115,26 @@ ErrorOr<void> Device::enumerate_device()
     dbgln_if(USB_DEBUG, "USB Device: Set address to {}", m_address);
 
     memcpy(&m_device_descriptor, &dev_descriptor, sizeof(USBDeviceDescriptor));
+
+    // Fetch the configuration descriptors from the device
+    m_configurations.ensure_capacity(m_device_descriptor.num_configurations);
+    for (auto configuration = 0u; configuration < m_device_descriptor.num_configurations; configuration++) {
+        USBConfigurationDescriptor configuration_descriptor;
+        transfer_length = TRY(m_default_pipe->control_transfer(USB_REQUEST_TRANSFER_DIRECTION_DEVICE_TO_HOST, USB_REQUEST_GET_DESCRIPTOR, (DESCRIPTOR_TYPE_CONFIGURATION << 8u) | configuration, 0, sizeof(USBConfigurationDescriptor), &configuration_descriptor));
+
+        if constexpr (USB_DEBUG) {
+            dbgln("USB Configuration Descriptor {}", configuration);
+            dbgln("Total Length: {}", configuration_descriptor.total_length);
+            dbgln("Number of interfaces: {}", configuration_descriptor.number_of_interfaces);
+            dbgln("Configuration Value: {}", configuration_descriptor.configuration_value);
+            dbgln("Attributes Bitmap: {:08b}", configuration_descriptor.attributes_bitmap);
+            dbgln("Maximum Power: {}mA", configuration_descriptor.max_power_in_ma * 2u); // This value is in 2mA steps
+        }
+
+        USBConfiguration device_configuration(*this, configuration_descriptor);
+        m_configurations.append(device_configuration);
+    }
+
     return {};
 }
 

Kernel/Bus/USB/USBDevice.h

@@ -8,11 +8,14 @@
 
 #include <AK/OwnPtr.h>
 #include <AK/Types.h>
+#include <AK/Vector.h>
+#include <Kernel/Bus/USB/USBConfiguration.h>
 #include <Kernel/Bus/USB/USBPipe.h>
 
 namespace Kernel::USB {
 
 class USBController;
+class USBConfiguration;
 
 //
 // Some nice info from FTDI on device enumeration and how some of this
@@ -55,6 +58,7 @@ protected:
     u16 m_vendor_id { 0 };                      // This device's vendor ID assigned by the USB group
     u16 m_product_id { 0 };                     // This device's product ID assigned by the USB group
     USBDeviceDescriptor m_device_descriptor {}; // Device Descriptor obtained from USB Device
+    Vector<USBConfiguration> m_configurations;  // Configurations for this device
 
     NonnullRefPtr<USBController> m_controller;
     NonnullOwnPtr<Pipe> m_default_pipe; // Default communication pipe (endpoint0) used during enumeration