diff --git a/board-support/raspberrypi-rp2040/src/hal/usb.zig b/board-support/raspberrypi-rp2040/src/hal/usb.zig
index 3177047..575a4d3 100644
--- a/board-support/raspberrypi-rp2040/src/hal/usb.zig
+++ b/board-support/raspberrypi-rp2040/src/hal/usb.zig
@@ -42,7 +42,6 @@ pub const utf8ToUtf16Le = usb.utf8Toutf16Le;
 
 pub var EP0_OUT_CFG: usb.EndpointConfiguration = .{
     .descriptor = &usb.EndpointDescriptor{
-        .length = @as(u8, @intCast(@sizeOf(usb.EndpointDescriptor))),
         .descriptor_type = usb.DescType.Endpoint,
         .endpoint_address = usb.EP0_OUT_ADDR,
         .attributes = @intFromEnum(usb.TransferType.Control),
@@ -57,7 +56,6 @@ pub var EP0_OUT_CFG: usb.EndpointConfiguration = .{
 
 pub var EP0_IN_CFG: usb.EndpointConfiguration = .{
     .descriptor = &usb.EndpointDescriptor{
-        .length = @as(u8, @intCast(@sizeOf(usb.EndpointDescriptor))),
         .descriptor_type = usb.DescType.Endpoint,
         .endpoint_address = usb.EP0_IN_ADDR,
         .attributes = @intFromEnum(usb.TransferType.Control),
diff --git a/core/src/core/usb.zig b/core/src/core/usb.zig
index a7b4e56..9f38ed9 100644
--- a/core/src/core/usb.zig
+++ b/core/src/core/usb.zig
@@ -511,9 +511,7 @@ pub const Dir = enum(u8) {
 };
 
 /// Describes an endpoint within an interface
-pub const EndpointDescriptor = extern struct {
-    /// Length of this struct, must be 7.
-    length: u8,
+pub const EndpointDescriptor = struct {
     /// Type of this descriptor, must be `Endpoint`.
     descriptor_type: DescType,
     /// Address of this endpoint, where the bottom 4 bits give the endpoint
@@ -530,7 +528,7 @@ pub const EndpointDescriptor = extern struct {
 
     pub fn serialize(self: *const @This()) [7]u8 {
         var out: [7]u8 = undefined;
-        out[0] = 7; // length
+        out[0] = out.len;
         out[1] = @intFromEnum(self.descriptor_type);
         out[2] = self.endpoint_address;
         out[3] = self.attributes;
@@ -542,9 +540,7 @@ pub const EndpointDescriptor = extern struct {
 };
 
 /// Description of an interface within a configuration.
-pub const InterfaceDescriptor = extern struct {
-    /// Length of this structure, must be 9.
-    length: u8,
+pub const InterfaceDescriptor = struct {
     /// Type of this descriptor, must be `Interface`.
     descriptor_type: DescType,
     /// ID of this interface.
@@ -566,7 +562,7 @@ pub const InterfaceDescriptor = extern struct {
 
     pub fn serialize(self: *const @This()) [9]u8 {
         var out: [9]u8 = undefined;
-        out[0] = 9; // length
+        out[0] = out.len;
         out[1] = @intFromEnum(self.descriptor_type);
         out[2] = self.interface_number;
         out[3] = self.alternate_setting;
@@ -580,9 +576,7 @@ pub const InterfaceDescriptor = extern struct {
 };
 
 /// Description of a single available device configuration.
-pub const ConfigurationDescriptor = extern struct {
-    /// Length of this structure, must be 9.
-    length: u8,
+pub const ConfigurationDescriptor = struct {
     /// Type of this descriptor, must be `Config`.
     descriptor_type: DescType,
     /// Total length of all descriptors in this configuration, concatenated.
@@ -610,7 +604,7 @@ pub const ConfigurationDescriptor = extern struct {
 
     pub fn serialize(self: *const @This()) [9]u8 {
         var out: [9]u8 = undefined;
-        out[0] = 9; // length
+        out[0] = out.len;
         out[1] = @intFromEnum(self.descriptor_type);
         out[2] = @intCast(self.total_length & 0xff);
         out[3] = @intCast((self.total_length >> 8) & 0xff);
@@ -625,9 +619,7 @@ pub const ConfigurationDescriptor = extern struct {
 
 /// Describes a device. This is the most broad description in USB and is
 /// typically the first thing the host asks for.
-pub const DeviceDescriptor = extern struct {
-    /// Length of this structure, must be 18.
-    length: u8,
+pub const DeviceDescriptor = struct {
     /// Type of this descriptor, must be `Device`.
     descriptor_type: DescType,
     /// Version of the device descriptor / USB protocol, in binary-coded
@@ -658,7 +650,7 @@ pub const DeviceDescriptor = extern struct {
 
     pub fn serialize(self: *const @This()) [18]u8 {
         var out: [18]u8 = undefined;
-        out[0] = 18; // length
+        out[0] = out.len;
         out[1] = @intFromEnum(self.descriptor_type);
         out[2] = @intCast(self.bcd_usb & 0xff);
         out[3] = @intCast((self.bcd_usb >> 8) & 0xff);
@@ -682,9 +674,7 @@ pub const DeviceDescriptor = extern struct {
 
 /// USB Device Qualifier Descriptor
 /// This descriptor is mostly the same as the DeviceDescriptor
-pub const DeviceQualifierDescriptor = extern struct {
-    /// Length of this structure, must be 18.
-    length: u8 = 10,
+pub const DeviceQualifierDescriptor = struct {
     /// Type of this descriptor, must be `Device`.
     descriptor_type: DescType = DescType.DeviceQualifier,
     /// Version of the device descriptor / USB protocol, in binary-coded
@@ -705,7 +695,7 @@ pub const DeviceQualifierDescriptor = extern struct {
 
     pub fn serialize(self: *const @This()) [10]u8 {
         var out: [10]u8 = undefined;
-        out[0] = 10; // length
+        out[0] = out.len;
         out[1] = @intFromEnum(self.descriptor_type);
         out[2] = @intCast(self.bcd_usb & 0xff);
         out[3] = @intCast((self.bcd_usb >> 8) & 0xff);
@@ -721,8 +711,6 @@ pub const DeviceQualifierDescriptor = extern struct {
 
 /// Layout of an 8-byte USB SETUP packet.
 pub const SetupPacket = extern struct {
-    /// Request type; in practice, this is always either OUT (host-to-device) or
-    /// IN (device-to-host), whose values are given in the `Dir` enum.
     request_type: u8,
     /// Request. Standard setup requests are in the `SetupRequest` enum.
     /// Devices can extend this with additional types as long as they don't
diff --git a/core/src/core/usb/hid.zig b/core/src/core/usb/hid.zig
index c63e28a..79f87d7 100644
--- a/core/src/core/usb/hid.zig
+++ b/core/src/core/usb/hid.zig
@@ -87,8 +87,7 @@ pub const DescType = enum(u8) {
 };
 
 /// USB HID descriptor
-pub const HidDescriptor = extern struct {
-    length: u8 = 9,
+pub const HidDescriptor = struct {
     descriptor_type: DescType = DescType.Hid,
     /// Numeric expression identifying the HID Class Specification release
     bcd_hid: u16,
@@ -103,7 +102,7 @@ pub const HidDescriptor = extern struct {
 
     pub fn serialize(self: *const @This()) [9]u8 {
         var out: [9]u8 = undefined;
-        out[0] = 9; // length
+        out[0] = out.len;
         out[1] = @intFromEnum(self.descriptor_type);
         out[2] = @intCast(self.bcd_hid & 0xff);
         out[3] = @intCast((self.bcd_hid >> 8) & 0xff);
diff --git a/examples/raspberrypi-rp2040/src/usb_device.zig b/examples/raspberrypi-rp2040/src/usb_device.zig
index 8f2d74e..4c25c48 100644
--- a/examples/raspberrypi-rp2040/src/usb_device.zig
+++ b/examples/raspberrypi-rp2040/src/usb_device.zig
@@ -38,7 +38,6 @@ fn ep1_out_callback(dc: *usb.DeviceConfiguration, data: []const u8) void {
 // add your own endpoints to...
 pub var EP1_OUT_CFG: usb.EndpointConfiguration = .{
     .descriptor = &usb.EndpointDescriptor{
-        .length = @as(u8, @intCast(@sizeOf(usb.EndpointDescriptor))),
         .descriptor_type = usb.DescType.Endpoint,
         .endpoint_address = usb.Dir.Out.endpoint(1),
         .attributes = @intFromEnum(usb.TransferType.Bulk),
@@ -55,7 +54,6 @@ pub var EP1_OUT_CFG: usb.EndpointConfiguration = .{
 
 pub var EP1_IN_CFG: usb.EndpointConfiguration = .{
     .descriptor = &usb.EndpointDescriptor{
-        .length = @as(u8, @intCast(@sizeOf(usb.EndpointDescriptor))),
         .descriptor_type = usb.DescType.Endpoint,
         .endpoint_address = usb.Dir.In.endpoint(1),
         .attributes = @intFromEnum(usb.TransferType.Bulk),
@@ -73,7 +71,6 @@ pub var EP1_IN_CFG: usb.EndpointConfiguration = .{
 // This is our device configuration
 pub var DEVICE_CONFIGURATION: usb.DeviceConfiguration = .{
     .device_descriptor = &.{
-        .length = @as(u8, @intCast(@sizeOf(usb.DeviceDescriptor))),
         .descriptor_type = usb.DescType.Device,
         .bcd_usb = 0x0110,
         .device_class = 0,
@@ -89,7 +86,6 @@ pub var DEVICE_CONFIGURATION: usb.DeviceConfiguration = .{
         .num_configurations = 1,
     },
     .interface_descriptor = &.{
-        .length = @as(u8, @intCast(@sizeOf(usb.InterfaceDescriptor))),
         .descriptor_type = usb.DescType.Interface,
         .interface_number = 0,
         .alternate_setting = 0,
@@ -101,9 +97,10 @@ pub var DEVICE_CONFIGURATION: usb.DeviceConfiguration = .{
         .interface_s = 0,
     },
     .config_descriptor = &.{
-        .length = @as(u8, @intCast(@sizeOf(usb.ConfigurationDescriptor))),
         .descriptor_type = usb.DescType.Config,
-        .total_length = @as(u8, @intCast(@sizeOf(usb.ConfigurationDescriptor) + @sizeOf(usb.InterfaceDescriptor) + @sizeOf(usb.EndpointDescriptor) + @sizeOf(usb.EndpointDescriptor))),
+        // This is calculated via the sizes of underlying descriptors contained in this configuration.
+        // ConfigurationDescriptor(9) + InterfaceDescriptor(9) * 1 + EndpointDescriptor(8) * 2
+        .total_length = 34,
         .num_interfaces = 1,
         .configuration_value = 1,
         .configuration_s = 0,
diff --git a/examples/raspberrypi-rp2040/src/usb_hid.zig b/examples/raspberrypi-rp2040/src/usb_hid.zig
index 752111a..6705054 100644
--- a/examples/raspberrypi-rp2040/src/usb_hid.zig
+++ b/examples/raspberrypi-rp2040/src/usb_hid.zig
@@ -38,7 +38,6 @@ fn ep1_out_callback(dc: *usb.DeviceConfiguration, data: []const u8) void {
 // add your own endpoints to...
 pub var EP1_OUT_CFG: usb.EndpointConfiguration = .{
     .descriptor = &usb.EndpointDescriptor{
-        .length = @as(u8, @intCast(@sizeOf(usb.EndpointDescriptor))),
         .descriptor_type = usb.DescType.Endpoint,
         .endpoint_address = usb.Dir.Out.endpoint(1),
         .attributes = @intFromEnum(usb.TransferType.Interrupt),
@@ -55,7 +54,6 @@ pub var EP1_OUT_CFG: usb.EndpointConfiguration = .{
 
 pub var EP1_IN_CFG: usb.EndpointConfiguration = .{
     .descriptor = &usb.EndpointDescriptor{
-        .length = @as(u8, @intCast(@sizeOf(usb.EndpointDescriptor))),
         .descriptor_type = usb.DescType.Endpoint,
         .endpoint_address = usb.Dir.In.endpoint(1),
         .attributes = @intFromEnum(usb.TransferType.Interrupt),
@@ -73,7 +71,6 @@ pub var EP1_IN_CFG: usb.EndpointConfiguration = .{
 // This is our device configuration
 pub var DEVICE_CONFIGURATION: usb.DeviceConfiguration = .{
     .device_descriptor = &.{
-        .length = @as(u8, @intCast(@sizeOf(usb.DeviceDescriptor))),
         .descriptor_type = usb.DescType.Device,
         .bcd_usb = 0x0200,
         .device_class = 0,
@@ -91,7 +88,6 @@ pub var DEVICE_CONFIGURATION: usb.DeviceConfiguration = .{
         .num_configurations = 1,
     },
     .interface_descriptor = &.{
-        .length = @as(u8, @intCast(@sizeOf(usb.InterfaceDescriptor))),
         .descriptor_type = usb.DescType.Interface,
         .interface_number = 0,
         .alternate_setting = 0,
@@ -103,9 +99,10 @@ pub var DEVICE_CONFIGURATION: usb.DeviceConfiguration = .{
         .interface_s = 0,
     },
     .config_descriptor = &.{
-        .length = @as(u8, @intCast(@sizeOf(usb.ConfigurationDescriptor))),
         .descriptor_type = usb.DescType.Config,
-        .total_length = @as(u8, @intCast(@sizeOf(usb.ConfigurationDescriptor) + @sizeOf(usb.InterfaceDescriptor) + @sizeOf(usb.EndpointDescriptor) + @sizeOf(usb.EndpointDescriptor))),
+        // This is calculated via the sizes of underlying descriptors contained in this configuration.
+        // ConfigurationDescriptor(9) + InterfaceDescriptor(9) * 1 + EndpointDescriptor(8) * 2
+        .total_length = 34,
         .num_interfaces = 1,
         .configuration_value = 1,
         .configuration_s = 0,