embassy-dfu-usb: Allow application and dfu feature at the same time

Since there is no technical reason to disallow the use of both features
at the same time, remove the artifical contraint to give developers
more freedom with their implementations.

Author: paroga

embassy-usb-dfu/CHANGELOG.md

@@ -8,6 +8,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 <!-- next-header -->
 ## Unreleased - ReleaseDate
 
+- Allow enabling the `application` and `dfu` feature at the same time
+
 ## 0.2.0 - 2025-08-27
 
 - First release with changelog.

embassy-usb-dfu/src/application.rs

@@ -1,3 +1,4 @@
+//! Application part of DFU logic
 use embassy_boot::BlockingFirmwareState;
 use embassy_time::{Duration, Instant};
 use embassy_usb::control::{InResponse, OutResponse, Recipient, RequestType};

embassy-usb-dfu/src/dfu.rs

@@ -1,3 +1,4 @@
+//! DFU bootloader part of DFU logic
 use embassy_boot::{AlignedBuffer, BlockingFirmwareUpdater, FirmwareUpdaterError};
 use embassy_usb::control::{InResponse, OutResponse, Recipient, RequestType};
 use embassy_usb::driver::Driver;

embassy-usb-dfu/src/lib.rs

@@ -6,21 +6,15 @@ mod fmt;
 pub mod consts;
 
 #[cfg(feature = "dfu")]
-mod dfu;
-#[cfg(feature = "dfu")]
+pub mod dfu;
+#[cfg(all(feature = "dfu", not(feature = "application")))]
 pub use self::dfu::*;
 
 #[cfg(feature = "application")]
-mod application;
-#[cfg(feature = "application")]
+pub mod application;
+#[cfg(all(feature = "application", not(feature = "dfu")))]
 pub use self::application::*;
 
-#[cfg(any(
-    all(feature = "dfu", feature = "application"),
-    not(any(feature = "dfu", feature = "application"))
-))]
-compile_error!("usb-dfu must be compiled with exactly one of `dfu`, or `application` features");
-
 /// Provides a platform-agnostic interface for initiating a system reset.
 ///
 /// This crate exposes `ResetImmediate` when compiled with cortex-m or esp32c3 support, which immediately issues a