usb: add add_class to builder, so that FooBarClass::new(&mut builder) can set up everything.

embassy-usb/Cargo.toml

@@ -10,3 +10,4 @@ defmt = { version = "0.3", optional = true }
 log = { version = "0.4.14", optional = true }
 cortex-m = "0.7.3"
 num-traits = { version = "0.2.14", default-features = false }
+heapless = "0.7.10"

embassy-usb/src/builder.rs

@@ -1,8 +1,11 @@
+use heapless::Vec;
+
 use super::class::UsbClass;
 use super::descriptor::{BosWriter, DescriptorWriter};
 use super::driver::{Driver, EndpointAllocError};
 use super::types::*;
 use super::UsbDevice;
+use super::MAX_CLASS_COUNT;
 
 #[derive(Debug, Copy, Clone)]
 #[cfg_attr(feature = "defmt", derive(defmt::Format))]
@@ -116,6 +119,7 @@ impl<'a> Config<'a> {
 /// Used to build new [`UsbDevice`]s.
 pub struct UsbDeviceBuilder<'d, D: Driver<'d>> {
     config: Config<'d>,
+    classes: Vec<&'d mut dyn UsbClass, MAX_CLASS_COUNT>,
 
     bus: D,
     next_interface_number: u8,
@@ -165,6 +169,7 @@ impl<'d, D: Driver<'d>> UsbDeviceBuilder<'d, D> {
         UsbDeviceBuilder {
             bus,
             config,
+            classes: Vec::new(),
             next_interface_number: 0,
             next_string_index: 4,
 
@@ -175,7 +180,7 @@ impl<'d, D: Driver<'d>> UsbDeviceBuilder<'d, D> {
     }
 
     /// Creates the [`UsbDevice`] instance with the configuration in this builder.
-    pub fn build(mut self, classes: &'d mut [&'d mut dyn UsbClass]) -> UsbDevice<'d, D> {
+    pub fn build(mut self) -> UsbDevice<'d, D> {
         self.config_descriptor.end_configuration();
         self.bos_descriptor.end_bos();
 
@@ -185,10 +190,16 @@ impl<'d, D: Driver<'d>> UsbDeviceBuilder<'d, D> {
             self.device_descriptor.into_buf(),
             self.config_descriptor.into_buf(),
             self.bos_descriptor.writer.into_buf(),
-            classes,
+            self.classes,
         )
     }
 
+    pub fn add_class(&mut self, class: &'d mut dyn UsbClass) {
+        if self.classes.push(class).is_err() {
+            panic!("max class count reached")
+        }
+    }
+
     /// Allocates a new interface number.
     pub fn alloc_interface(&mut self) -> InterfaceNumber {
         let number = self.next_interface_number;

embassy-usb/src/lib.rs

@@ -14,6 +14,7 @@ pub mod types;
 mod util;
 
 use class::ControlInRequestStatus;
+use heapless::Vec;
 
 use self::class::{RequestStatus, UsbClass};
 use self::control::*;
@@ -53,6 +54,8 @@ pub const CONFIGURATION_VALUE: u8 = 1;
 /// The default value for bAlternateSetting for all interfaces.
 pub const DEFAULT_ALTERNATE_SETTING: u8 = 0;
 
+pub const MAX_CLASS_COUNT: usize = 4;
+
 pub struct UsbDevice<'d, D: Driver<'d>> {
     bus: D::Bus,
     control: D::ControlPipe,
@@ -67,7 +70,7 @@ pub struct UsbDevice<'d, D: Driver<'d>> {
     self_powered: bool,
     pending_address: u8,
 
-    classes: &'d mut [&'d mut dyn UsbClass],
+    classes: Vec<&'d mut dyn UsbClass, MAX_CLASS_COUNT>,
 }
 
 impl<'d, D: Driver<'d>> UsbDevice<'d, D> {
@@ -77,7 +80,7 @@ impl<'d, D: Driver<'d>> UsbDevice<'d, D> {
         device_descriptor: &'d [u8],
         config_descriptor: &'d [u8],
         bos_descriptor: &'d [u8],
-        classes: &'d mut [&'d mut dyn UsbClass],
+        classes: Vec<&'d mut dyn UsbClass, MAX_CLASS_COUNT>,
     ) -> Self {
         let control = driver
             .alloc_control_pipe(config.max_packet_size_0 as u16)