Remove length fields as they are obsolete. The lengths is only required

during the serialization and therefore is already hardcoded. The only
other convinience is the calculation of the descriptor size, but this is
already wrong. extern structs are padded and therefore do not have the
right sizes.

Signed-off-by: Tobias Kohlbau <[email protected]>

build/build.zig

@@ -523,7 +523,6 @@ pub const BuildEnvironment = struct {
         if (options.target.configure) |configure| {
             configure(fw.env, fw);
         }
-
 
         return fw;
     }

core/src/core/usb.zig

@@ -11,6 +11,7 @@
 //! 5. Call `usb.task()` within the main loop
 
 const std = @import("std");
+const sizeOfCheck = @import("../core.zig").sizeOfCheck;
 
 /// USB Human Interface Device (HID)
 pub const hid = @import("usb/hid.zig");
@@ -511,9 +512,7 @@ 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 = 7,
+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 +529,7 @@ pub const EndpointDescriptor = extern struct {
 
     pub fn serialize(self: *const @This()) [7]u8 {
         var out: [7]u8 = undefined;
-        out[0] = self.length;
+        out[0] = out.len;
         out[1] = @intFromEnum(self.descriptor_type);
         out[2] = self.endpoint_address;
         out[3] = self.attributes;
@@ -542,9 +541,7 @@ 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 = 9,
+pub const InterfaceDescriptor = struct {
     /// Type of this descriptor, must be `Interface`.
     descriptor_type: DescType,
     /// ID of this interface.
@@ -566,7 +563,7 @@ pub const InterfaceDescriptor = extern struct {
 
     pub fn serialize(self: *const @This()) [9]u8 {
         var out: [9]u8 = undefined;
-        out[0] = self.length;
+        out[0] = out.len;
         out[1] = @intFromEnum(self.descriptor_type);
         out[2] = self.interface_number;
         out[3] = self.alternate_setting;
@@ -580,9 +577,7 @@ 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 = 9,
+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 +605,7 @@ pub const ConfigurationDescriptor = extern struct {
 
     pub fn serialize(self: *const @This()) [9]u8 {
         var out: [9]u8 = undefined;
-        out[0] = self.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 +620,7 @@ 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 = 18,
+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 +651,7 @@ pub const DeviceDescriptor = extern struct {
 
     pub fn serialize(self: *const @This()) [18]u8 {
         var out: [18]u8 = undefined;
-        out[0] = self.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 +675,7 @@ 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 +696,7 @@ pub const DeviceQualifierDescriptor = extern struct {
 
     pub fn serialize(self: *const @This()) [10]u8 {
         var out: [10]u8 = undefined;
-        out[0] = self.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 +712,6 @@ 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

core/src/core/usb/hid.zig

@@ -42,6 +42,7 @@
 //! The HID descriptor identifies the length and type of subordinate descriptors for device.
 
 const std = @import("std");
+const sizeOfCheck = @import("../../core.zig").sizeOfCheck;
 
 // +++++++++++++++++++++++++++++++++++++++++++++++++
 // Common Data Types
@@ -87,8 +88,7 @@ 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 +103,7 @@ pub const HidDescriptor = extern struct {
 
     pub fn serialize(self: *const @This()) [9]u8 {
         var out: [9]u8 = undefined;
-        out[0] = self.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);

examples/raspberrypi-rp2040/src/usb_device.zig

@@ -98,7 +98,9 @@ pub var DEVICE_CONFIGURATION: usb.DeviceConfiguration = .{
     },
     .config_descriptor = &.{
         .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,

examples/raspberrypi-rp2040/src/usb_hid.zig

@@ -100,7 +100,9 @@ pub var DEVICE_CONFIGURATION: usb.DeviceConfiguration = .{
     },
     .config_descriptor = &.{
         .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,