Updating PR after review

src/device_builder.rs

@@ -33,6 +33,8 @@ pub enum BuilderError {
     InvalidPacketSize,
     /// Configuration specifies higher USB power draw than allowed
     PowerTooHigh,
+    /// The provided control buffer is too small for the provided maximum packet size.
+    ControlBufferTooSmall,
 }
 
 /// Provides basic string descriptors about the device, including the manufacturer, product name,
@@ -110,8 +112,16 @@ impl<'a, B: UsbBus> UsbDeviceBuilder<'a, B> {
     }
 
     /// Creates the [`UsbDevice`] instance with the configuration in this builder.
-    pub fn build(self) -> UsbDevice<'a, B> {
-        UsbDevice::build(self.alloc, self.config, self.control_buffer)
+    pub fn build(self) -> Result<UsbDevice<'a, B>, BuilderError> {
+        if self.control_buffer.len() < self.config.max_packet_size_0 as usize {
+            return Err(BuilderError::ControlBufferTooSmall);
+        }
+
+        Ok(UsbDevice::build(
+            self.alloc,
+            self.config,
+            self.control_buffer,
+        ))
     }
 
     builder_fields! {
@@ -194,6 +204,10 @@ impl<'a, B: UsbBus> UsbDeviceBuilder<'a, B> {
             _ => return Err(BuilderError::InvalidPacketSize),
         }
 
+        if self.control_buffer.len() < max_packet_size_0 as usize {
+            return Err(BuilderError::ControlBufferTooSmall);
+        }
+
         self.config.max_packet_size_0 = max_packet_size_0;
         Ok(self)
     }

src/lib.rs

@@ -158,7 +158,7 @@ pub mod endpoint;
 ///         .product("Serial port")])
 ///         .expect("Failed to set strings")
 ///     .device_class(usb_serial::DEVICE_CLASS)
-///     .build();
+///     .build().unwrap();
 ///
 /// // At this point the USB peripheral is enabled and a connected host will attempt to enumerate
 /// // it.

src/test_class.rs

@@ -96,7 +96,7 @@ impl<B: UsbBus> TestClass<'_, B> {
 
     /// Convenience method to create a UsbDevice that is configured correctly for TestClass.
     pub fn make_device<'a>(&self, usb_bus: &'a UsbBusAllocator<B>) -> UsbDevice<'a, B> {
-        self.make_device_builder(usb_bus).build()
+        self.make_device_builder(usb_bus).build().unwrap()
     }
 
     /// Convenience method to create a UsbDeviceBuilder that is configured correctly for TestClass.