1 files changed, 7 insertions, 1 deletions

diff --git a/embassy-usb-dfu/src/application.rs b/embassy-usb-dfu/src/application.rs
index 6ad07a78c..4b7b72073 100644
--- a/embassy-usb-dfu/src/application.rs
+++ b/embassy-usb-dfu/src/application.rs
@@ -2,7 +2,7 @@ use embassy_boot::BlockingFirmwareState;
 use embassy_time::{Duration, Instant};
 use embassy_usb::control::{InResponse, OutResponse, Recipient, RequestType};
 use embassy_usb::driver::Driver;
-use embassy_usb::{Builder, Handler};
+use embassy_usb::{Builder, FunctionBuilder, Handler};
 use embedded_storage::nor_flash::NorFlash;
 
 use crate::consts::{
@@ -130,8 +130,14 @@ pub fn usb_dfu<'d, D: Driver<'d>, MARK: DfuMarker, RST: Reset>(
     builder: &mut Builder<'d, D>,
     handler: &'d mut Control<MARK, RST>,
     timeout: Duration,
+    func_modifier: impl Fn(&mut FunctionBuilder<'_, 'd, D>),
 ) {
     let mut func = builder.function(0x00, 0x00, 0x00);
+
+    // Here we give users the opportunity to add their own function level MSOS headers for instance.
+    // This is useful when DFU functionality is part of a composite USB device.
+    func_modifier(&mut func);
+
     let mut iface = func.interface();
     let mut alt = iface.alt_setting(USB_CLASS_APPN_SPEC, APPN_SPEC_SUBCLASS_DFU, DFU_PROTOCOL_RT, None);
     let timeout = timeout.as_millis() as u16;